Deterrents And Reinforcement The Psychology Of Insufficient Reword

DOUGLAS H. LAWRENCE
LEON FESTINGER

tfirciir, .aid Reinforcement
The Psychology of Insufficient Reward

DOUGLAS H, LAWRENCE AND
LEON FESTINGER

Leon Festinger's theory of cognitive
dissonance has been widely recognized
as an important and influential concept
in certain areas of motivation and social
psychology, The theory of dissonance is
here applied to the problem of why par-
tial reward, delay of reward, and effort
expenditure during training result in in-
creased resistance to extinction.

The authors contend that a state of
impasse exists within learning theory
largely because some of its major as-
sumptions stand in apparent opposition
to certain well-established experimental
results. They put forward in this book
a new theory that seems to reconcile
these data and assumptions. This new
theory, the authors maintain, can account
for data with which other theories have
difficulty, it integrates empirical phe-
nomena that have been regarded as un-
related, and it is supported by the results
of experiments designed specifically to
test its implications. These experiments
are fully described in the text.

The authors present a critical review
as well as new data on alternative ex-
planations, and In the final chapter take
a look at the broader implications of the
new theory.

The authors are Professors of Psy-
chology at Stanford University.

15*- lAM 62-11898

Lawence

Deterrents and reinforcement

DETERRENTS

AND

REINFORCEMENT

Stanford Studies in Psychology, II

EDITORS

Robert R. Sears

Leon Festinger

Douglas H. Lawrence

DETERRENTS

and

REINFORCEMENT

The Psychology of Insufficient Reward

Douglas H. Lawrence

and

Leon Festinger

STANFORD UNIVERSITY PRESS

STANFOED, CALIFORNIA
1962

Stanford University Press
Stanford, California

1962 by the Board of Trustees of the
Leland Stanford Junior University

AH rights reserved

Library of Congress Catalog Card Number; 62-8664
Printed in the United States of America

Preface

About four years ago it occurred to us that the theory of dis-
sonance, which seems to explain some unusual human behavior
quite well, might be relevant to some bothersome data concern-
ing extinction in animals. Our enthusiasm for the idea was not,
at the time, completely unrestrained. On the one hand, the idea
seemed to have good possibilities of explaining some of the
theoretical problems connected with the consequences of partial
reward. On the other hand, it seemed somewhat unusual to
apply a theory developed on the basis of human behavior to
explain rat behavior. And, in addition, could we seriously as-
sume that rats reacted to dissonance in the way that human
beings do?

Nevertheless, we proceeded to investigate the idea. We
searched the existing literature and were encouraged. We
started to do some preliminary, exploratory experiments of our
own and were further encouraged. The present book reports
the results of our four years of research. In the course of these
four years our ideas became considerably clarified, suggesting
new extensions of the theory, and new experiments. We per-
formed a total of sixteen experiments which are reported in
this book.

It would be unfortunate to give the impression that this book
is solely the product of the two authors. A number of people
were active collaborators in the experimentation. A majority of
the experiments we report were done in collaboration with
John M. Theios and Edward Uyeno. Theios was also responsible

VI PREFACE

for the idea of the "partially placed" condition in Experiment 15.

There were many others who also helped in various aspects
of the experimental work. We should like to express our thanks
to Elaine Hatfield, William Lawton, Peter Poison, James Schoon-
ard, Bernard Sjoberg, Herbert Smith, Laurence Stettner, and
Neil Sullivan. We also wish to thank Gordon H. Bower, William
K. Estes, Frank J. Restle, and Robert R. Sears for reading the
manuscript of this book and offering many constructive and
helpful suggestions.

We should also like to express our appreciation to the Na-
tional Institutes of Health (Grant M-1689 to Douglas H. Law-
rence) and to the Ford Foundation ( a grant to Leon Festinger )
for liberally supporting our work.

DOUGLAS H. LAWRENCE
LEON FESTINGER
PALO ALTO, CALIFOBNIA
July 4, 1961

Contents

1. An Impasse for Learning Theory 1

2. Dissonance Reduction Effects in Learning Situations 30

3. Evidence for the Development of Attractions 60

4. Cumulative Effects of Dissonance Reduction 84

5. The Effects of a Zero Reward Schedule 103

6. The Effect of Weak Drive States 116

7. Effort, Expectation, and Amount of Reward 139

8. A Speculative Summary 156
References 171
Index 177

DETERRENTS

AND

REINFORCEMENT

1

An Impasse for Learning Theory

A ma|oi:.function of theory in jmy science Js the integration and
explanation^oF^erse empirical relationships. La its early stages
aTcientific tiEeory may deal with a few variables in an attempt
to account for data in a delimited area. When a theory becomes
highly developed it usually encompasses a large number of var-
iables and, from the hypothesized interrelationships among these
variables, is able to integrate and explain a large number of ob-
served phenomena. Needless to say, the growth of a theory from
its beginning stages to a point where it may be termed highly
developed is beset with many difficulties. The course of devel-
opment is never smooth.

No sooner does a theory establish itself as being able to ex-
plain a given body of data than there begins to appear evidence
that is apparently inconsistent with it. Sometimes this new evi-
dence points to a new variable that must be incorporated into
the theory; sometimes the new evidence leads to a minor modi-
fication of the assumptions underlying the theory; and some-
times there is no clear way to change or enlarge the theory so
as to take into account the new and contradictory evidence.
When the latter is the case, the theory usually continues to be
developed along its own lines, contradictory evidence simply
being ignored. But this new evidence also continues to accumu-
late until it is no longer merely "hew" but is an established and
considerable body of knowledge. Then an impasse is reached.
Progress becomes very difficult until some major modification
or extension of the theory is invented. In the^field of psychology
there are few theories that have beien developed ,ta a point

2 AN IMPASSE FOR LEABNING THEORY

where such an impasse is even possible. In the field of learn-
ing, however, theory has been developed this far. And, unfor-
tunately, just such an impasse has been reached.

It is the purpose of this chapter to point out the nature and
locus of this impasse. We shall review first some of the major
assumptions underlying learning theory. We shall then show
that these assumptions stand in apparent opposition to some
well-established experimental results.

It will be the purpose of the remainder of this volume to
suggest a major theoretical extension that reconciles these data
and assumptions. In addition, we shall present a considerable
amount of new data that provides added support for the theo-
retical extension we are offering.

The Focus of Learning Theory

It is difficult to summarize "learning theory" in general since
there is still no single uniformly accepted theoretical statement.
There is, however, a core of theory that stems from the work of
Hull (1943). Although there are exceptions among learning
theorists, these core assumptions are widely accepted, and it is
this core to which we shall address ourselves.

Darning theory is, of course, concerned basically with the
explanation of how the behavipr of an organism is progressively
modified as the result of experiential factors. Such modification
of behavior obviously involves increasing frequency of some
actions and decreasing frequency of other actions in any given
situation. In giving a theoretical account of .such changes, it
proveiiisefuljvery early in the development of learning theory
to think in terms of a concept that may be called "response
strength," representing the magnitude of the tendency for a
given response to be evoked in a given situation, It, of course,
became necessary to specify how response strength can be meas-
ured. Three measures of response strength have been commonly
used. All of them are plausible and have been proved valid
by data.

1. Relative frequency of^esponse.It has been plausibly ar-
gued that the stronger a response tendency is, the more likely
is the response to be elicited by the stimulus with which it is

AN IMPASSE FOR LEARNING THEORY 3

associated. In the early stages of establishing an association be-
tween a stimulus and a response this does indeed seem to be a
good measure. For example, in discrimination-learning prob-
lems, maze-learning situations, or situations where the organism
has to learn to make one of a number of possible instrumental
responses, the relative frequency with which the response oc-
curs upon presentation of the stimulus is an excellent indicator of
the course of learning. The data show that as the number of
stimulus-response sequences that have been rewarded increases,
there is an increase in the likelihood that the "correct" response
will be elicited upon a subsequent presentation of the stimulus.
This measure of response strength, however, seems to be a sen-
sitive measure only rather early in the learning process.

2. Latency of response. It has been plausibly argued that
the stronger the response strength the less time will elapse be-
tween presentation of the stimulus and the elicitation of the
response. This measure has proved to be rather generally useful
and also quite sensitive. As the number of rewarded stimulus-
response sequences increases, the latency of the response be-
comes shorter and shorter until it reaches some stable value.
At the beginning stages of learning there are usually very
marked changes in latency, and, in addition, this measure con-
tinues to show progressive changes toward shorter and shorter
times, even after relative frequency of response has reached 100
per cent.

3. Resistance to extinction. A third generally accepted
measure of response strength is resistance to extinction. Let us
imagine that a given stimulus-response sequence has been re-
warded a large number of times and, consequently, the response
strength is relatively strong. If we continued to elicit the re-
sponse by presenting the stimulus, but never again provided any
reward in the situation, we would expect the animal to persist
in its behavior until the response strength had weakened suffi-
ciently. Starting with a response of considerable strength, it
might take many trials before the animal stopped responding.
On the other hand, if the response strength had been quite weak
at the beginning of the series of unrewarded elicitations of the
response, we would expect extinction to occur much more rap-
idly. Thus, the resistance that the animal shows to extinction

4 AN IMPASSE FOR IJEAKNJNG THEORY

can be taken as a measure of the response strength, at the be-
ginning of the series of unrewarded experiences.

Thus, we have three measures of response strength.* Al-
though all of these measures are operationally independent,
theoretically they are all measures of the same thing and should,
of course, be interrelated in predictable ways. As response
strength increases because of the occurrence of stimulus-re-
sponse sequences followed by reward, the relative frequency
of response should increase, latency of response should simul-
taneously decrease, and subsequent tests should show that the
response is more resistant to extinction. It is, of course, possible
to uncorrelate these three measures, as shown by the work of
Logan (1960) and others, and clearly each of these is more
appropriate to some experimental arrangements than to others.
Nonetheless, these relationships do tend to be characteristic of
most learning situations.

With the use of this concept of response strength, the basic
task for the field of learning became the specification of those
variables that strengthen and those that weaken it. The prob-
lem for learning theory was to integrate these variables into a
useful explanatory system. Over the years a number of fairly
extensive theories have been developed that effectively deal
with many of these variables. These theories differ in a variety
of aspects, but they do have many assumptions in common.
This is not surprising since they all try to account for the same
set of experimental results. These assumptions, held in common
by most theorists., are, however, precisely the ones that seem to
be clearly contradicted by a variety of empirical findings. In
reviewing these assumptions, we shall be very brief, ignoring
many of the more subtle points of controversy and interpreta-
tion that have centered around them.

1. The function ofjeward.It has been known for a long
time thaf if an organism is motivated, perhaps by hunger, and
some response that it makes is followed by an appropriate re-

* A f ourth measure of "response strength," namely, amplitude of response,
has also been employed frequently. Since this particular measure is not relevant
to the lands of experimental situations with which we shall deal, we shall not
discuss it further.

AN IMPASSE FOR LEARNING THEORY 5

ward, such as food, the likelihood that the organism will per-
form this action again is increased. Thus, most theories of learn-
ing propose that if ? in a given situation, a response is followed
by reward, the response strength increases. It is also well known
that if a response in a situation is not followed by a reward ap-
propriate to the motivation of the organism, the likelihood that
the organism will again perform that action is diminished.
Learning theory has therefore adopted a proposition to deal
appropriately with this phenomenon. In short, in order to ac-
count for known data concerning rewards in a learning situa-
tion, learning theory proposes that if a response is followed by
a reward, response strength is increased; if not followed by a
reward, response strength is decreased. This basic proposition
has been very useful in helping to explain a good deal of data.

2. Delay of reward. It has been observed many times that
if a reward follows a given response almost immediately, learn-
ing is very rapid* On the other hand, if there is a temporal de-
lay between the response and the reward, learning proceeds
more slowly. In experiments on discrimination learning in rats,
for example, a delay of even a few seconds between the response
and the reward produces a considerable decrement in the rate
at which the response is learned. In order to account for these
data, learning theories generally agree on what may be called a
"gradient of reward effect." The theoretical proposition is that
a given reward produces the greatest increment of response
strength if the reward immediately follows the response. The
longer the time that elapses -between the performance of the
response and the occurrence of the reward^ the smaQefTs^the
ensuing increment in response strength. This theoretical state-
ment has been tested extensively, and we may feel confident
that it is valid.

3. Effort expenditure. lihere is one more variable that we
should like to mention at this point. Although it is not nearly
so central to learning theory as the two variables we have
already discussed, nevertheless it is important and well docu-
mented. Experimental studies have shown rather consistently
that the more effort a response dei^ajCtds, the less willing is the
animal to make the response. Learning tends to proceed more

6 AN IMPASSE FOR LEARNING THEORY

slowly the greater the effort involved in the response. Some
theories of learning have proposed that effort increases response
inhibition. Other theories have been inclined to regard effort
as a negative incentive. But, in one form or another, most learn-
ing theories include the proposition that increased effort weak-
ens the response strength.

These three variables reward, delay of reward, and effort-
fulness of response are, of course, only a small part of what is
dealt with by learning theory. We have mentioned these three
because they are the ones that are so integrally involved in the
theoretical difficulties with which we are concerned.

A Major Difficulty for Learning Theory

Recently, there has accumulated a considerable body of ex-
perimental evidence suggesting that these common assumptions
underlying learning theory fail to give an adequate description
of changes in response strength. In fact, there is the suggestion
that under some circumstances the variables of reward, tempo-
ral delay, and effort may have just the opposite effects from
those predicted by the assumptions we have outlined. The prob-
lem, and its seriousness, can best be illustrated by describing
three lines of experimental work.

1. The effects of partial regard!. Partial reward refers to a
training procedure in which only a proportion of the stimulus-
response sequences are rewarded: the occurrences of rewarded
and unrewarded trials are randomly determined so that an ani-
mal cannot anticipate the outcome on any given trial. For in-
stance, a hungry rat may be trained to run a maze in order to
find food in the goal box. If this training is done by means of
a 50 per cent reward schedule, there will be food in the goal
box on only half the trials. On the other half of the trials, the
box will be empty. The important theoretical issue centers about
the question of the response strength at the end of training when
a partial reward schedule has been used in contrast to a 100 per
cent reward schedule, that is, one on which the animal is re-
warded on every trial.

The theoretical issue was forced on the attention of learning
theorists by the early studies of Humphreys (1939) and others

AN IMPASSE FOR LEARNING THEORY 7

(c. Jenkins and Stanley, 1950, and Lewis, 1960). It became
apparent that there was a direct conflict between theory and
data. Learning theory predicted that performance should be of
maximum strength with a 100 per cent reward schedule, in
which every trial was rewarded, and of less strength after a
partial reward schedule in which rewarded and unrewarded
trials are intermixed. The experimental data, on the other hand,
indicated that just the converse was true. A partial reward
schedule established a stronger performance than did continu-
ous reward when response strength was measured by resistance
to extinction. These data indicated that there was something
wrong with those theoretical assumptions that say response
strength increases as the number of reward experiences in-
creases, and decreases with the accumulation of non-reward ex-
periences.

To make the issue somewhat more concrete, let us review a
recent study done by Weinstock ( 1954 ) . He trained four groups
of hungry rats to run an alleyway for food. The percentage of
trials on which each group was rewarded was, respectively, 100
per cent, 80 per cent, 50 per cent, and 30 per cent. Only one
trial a day was given until each animal had had 75 trials. All
groups were then run for an additional 20 trials without reward.
On each trial of training and extinction a speed score was re-
corded.

Under these training conditions, it is clear what the assump-
tions underlying learning theory should predict about the
strength of performance at the end of 75 trials. The 100 per
cent reward group has had 75 rewarded trials, and if perform-
ance strength is a cumulative function of reward, this group
should show the strongest tendency to run and to persist in this
response. On the other hand, the 30 per cent reward group has
had only about 23 rewarded trials, far fewer than the 100 per
cent reward group, in which to build up performance strength.
Furthermore, it has had 52 unrewarded trials, each of which
should have subtracted from the response strength. Conse-
quently, at the end of training it should show relatively poor
performance as measured both by the latency of the response
and by resistance to extinction.

8 AN IMPASSE FOR LEARNING THEORY

The main results of this study only partially support this
theoretical expectation. At the end of training the speed scores
indicated that the 100 per cent reward group was, indeed, fast-
est. Then came the 80 per cent, 50 per cent, and 30 per cent
reward groups, in order. Thus, in terms of this latency or speed
measure there is good support for the theoretical prediction that
the more frequently rewarded group should have the stronger
tendency to run. However, if we look at a measure of resistance
to extinction we get just the opposite ordering of the groups.
Using an arbitrary criterion of extinction ( a speed score of . 2 ) ,
this criterion is reached on the fourth trial by the 100 per cent
group, on the twelfth trial by the 80 per cent group, on the
eighteenth trial by the 50 per cent group, and not at all during
the twenty trials by the 30 per cent reward group. Thus, there
are clear and marked differences among the groups in their
tendency to persist in this behavior. The group rewarded most
infrequently was the most resistant to extinction. In theoretical
terms, it means thajtihe partially rewarded groups had greater
response strength than did the 100 per cent reward group. These
results^are very difficult to reconcile with the theories of learn-
ing.

There is nothing artifactual about the Weinstock experi-
ment. The same results occur over and over again in the litera-
ture. In most of these studies, we find that at the end of ^training
the 100 per cent reward group runs faster than the partially re-
warded group, fust as in Weinstock's experiment. And in prac-
tically all studies, the partially rewarded group is more resistant
to extinction than is the 100 per cent reward group.

2. The efectpf delay of reward. A. similar and equally dif-
ficult problem confronts us in a number of recent studies on de-
lay of reward. This latter term refers to a training, procedure in
which an interval of time is interposed between the performance
of the response and the presentation of the reward. For ex-
ample, a hungry animal may be trained to run to a goal box
where it is restrained for twenty to thirty seconds before being
given food. As we have indicated previously, learning theory
assumes that the longer this delay of reward, the smaller is the
increment of response strength. Rewards are most effective

AN IMPASSE FOR LEARNING THEORY 9

when they are immediate. It has been known for a long time
that delay of reward during training slows the rate of learning
and produces relatively long latencies in the performance of the
response. It is precisely these findings that give strong support
to some of the assumptions of learning theory.

Recently, however, there have been investigations of the
effect of these delays on resistance to extinction. When this
measure of response strength is used, the experimental results
are again in direct opposition to our theoretical expectations.
A group of animals trained with delay intervals between the re-
sponse and the reward shows more persistence during extinction
than does a comparable group that has had immediate reward
on each training trial. This finding has been replicated suffi-
ciently often by now that we can have complete faith in it. But
if this is true, it contradicts learning theory. It indicates that a
delay in reward has increased, not decreased, the strength of
the tendency to perform the response.

The problem involved can best be underlined by describing
an experiment on delay of reward. Wike and McNamara ( 1957 )
did a study to determine the effect on resistance to extinction
of differing percentages of trials on which delay of reward was
present. They trained three groups of hungry animals on a run-
way. One group was delayed for thirty seconds on 25 per cent
of the trials before entering the goal box and finding food. On
the remaining trials, no delay at all was involved. These delay
and no-delay trials occurred in an unpredictable order. The
second group was delayed for thirty seconds on 50 per cent of
its trials, and the third group on 75 per cent of its trials.

According to learning theory, we should expect the third
group, which experienced the greatest number of delays, to
have the weakest response strength and the first group, which
experienced the fewest delay trials, to have the strongest. Again
we find that measures of latency of response during training
support the learning theory prediction. At the end of 28 train-
ing trials, the running times were fastest for the group with the
least percentage of delay and slowest for the group with the
greatest percentage of delay. However, once more we find a
contradiction between theory and performance during extinc-

10 AN IMPASSE FOR LEARNING THEOHY

tion. Resistance to extinction is least for those with the fewest
delay trials (25 per cent delay group) and greatest for those
with the most delay trials ( 75 per cent delay group ) . Thus, this
study clearly indicates that the more frequently an animal has
experieucecLdelay of reward the greater is its persistence during
extinction. This outcome is very difficult to reconcile with the
assumptions that learning theory makes about the effects of the
gradient of reward on response strength.

It should be emphasized that this type of result has been
obtained so frequently that it can be accepted as a generaliza-
tion. The partial delay aspect of the above experiment is not a
crucial feature. The same result obtains even when one group
is delayed on each training trial and the other group is never
delayed (Fehrer, 1956). Thus, granting that resistance to ex-
tinction is a valid index of response strength, we are confronted
by the dflemma that delay of reward strengthens performance
when on theoretical grounds we have every right to expect that
it would weaken it.

3. The effect ofefort.K third area of conflict between the-
ory and empirical findings concerns the effect of effort on re-
sponse strength. Here it must be granted that the experimental
evidence is scanty. Nonetheless, there are sufficient data to sug-
gest that future findings will be a source of embarrassment to
learning theory.

We have indicated that effort is conceptualized in learning
theory as a negative incentive or else as a variable that builds
up an inhibitory state opposing the response being learned. In
either instance we should expect that the more effort required
of the animal in order to obtain a given reward, the weaker
would be its response strength. And data show that effortful
responses are usually learned more slowly and show longer la-
tencies than non-effortful ones. The source of conflict between
learning theory and data here again only becomes apparent
when we look at the effect of effort on persistence during ex-
tinction.

One of the most clear-cut studies on the effect of effort is
reported by Aiken (1957). He used an apparatus where the
animal had to press against a panel in order to obtain a pellet
of food. The pressure, and thus the effort, required to activate

AN IMPASSE FOR LEARNING THEORY 11

the panel could be varied. For one group of animals, 32 grams
of pressure were required during training whereas for the other
group only 5 grams were required. After training, the animals
were extinguished to a criterion of two consecutive failures to
respond within thirty seconds. During the extinction trials half
of each training group was required to exert 5 grains of pressure
and the other half, 32 grams of pressure.

The 5-gram and the 32-gram training groups differ, as one
would expect, in how quickly they learn. The group exerting
greater effort learns more slowly. During extinction, however,
there are clear differences in persistence that are contrary to
theoretical expectation. The data from this experiment are
shown in Table 1 . 1.

TABLE 1.1

AVERAGE NUMBER OF TRIALS TO EXTINCTION
(From Aiken, 1957)

Effort

During Effort During Acquisition

Extinction 5 grams 32 grams

5 grams 45.5 56.5

32 grams 35.6 46.8

Let us look first at the figures in the upper left and lower
right quadrants. It is clear from the data that when animals are
extinguished under the same effort condition on which they
were trained, there is no difference in resistance to extinction.
This is true even though for one group 32 grams of effort is in-
volved and for the other only 5 grams. This is in itself some-
what surprising. If effort is a negative incentive, then a group
trained and extinguished on 32 grams should certainly have
less response strength than one trained and extinguished on 5
grams. This same type of result has been found by Weiss ( 1961 ) ,
Maatsch, Adelman, and Denny (1954), and others.

Of even more importance, however, is the comparison be-
tween columns in the table. Within either row, we can compare
two groups that were extinguished under exactly the same effort
condition; they differ only with respect to the effort they had
expended during training. In each of the two comparisons, the
group that expended the most effort during training takes more
trials to reach the criterion of extinction. If this result proves

12 AN IMPASSE FOR LEARNING THEORY

to be valid, it is disconcerting from the viewpoint of the assump-
tions of learning theory. The more effort the animal is required
to expend during training, the less should be the strength of its
response. Why, then, does it persist longer during extinction?

This brief survey is sufficient to indicate that there is a con-
siderable body of data that represents a persistent irritant to
the learning theorist. It is clear that partial reward, delay of
reward, and effort are variables that increase resistance to ex-
tinction when theoretically they should decrease it.

We should like to emphasize the fundamental quality of this
conflict between fact and theory. First of all, it is not as though
these findings were concerned with complex phenomena rela-
tively remote from the main areas of learning theory. If they
were, we could always console ourselves with the thought that
they would eventually fall into place once our theories were de-
veloped sufficiently to deal with them. Unfortunately, however,
these results concern phenomena that are directly within the
province of our present theories. And these theories, as they
are presently formulated, make clear-cut predictions as to what
should occur. The conflict between fact and prediction cannot
be ignored.

Second, and probably more important, the strategy for
handling this contradiction is not clear. It is simple enough to
say that when a well-established fact contradicts a theoretical
prediction, the assumptions of the theory should be changed.
But in the present instance this procedure might well result in
a very great loss for relatively little gain. The present assump-
tions of learning theory do account in an adequate manner for
a wide range of behavior. Even more significantly, they do ac-
count adequately for some aspects of the data from partial re-
ward, delay of reward, and effort studies. For instance, they dp
predict the_slqwer learning and the longer latencies that nor-
mally are observed whenthese variables are introduced into the
training procedure. What they fail primarily to predict is one
aspect of these studies, namely, the effect of these variables on
resistance to extinction. Consequently, it is not at all clear that
we can make a simple change in assumptions to account for the
latter effects without giving up the present predictive power for
the other aspects of the behavior.

AN IMPASSE FOR LEARNING THEORY 13

At first glance it would appear that we might circumvent the
apparent contradiction by contending that resistance to extinc-
tion is a poor measure of response strength. This approach is
totally unacceptable, however, because it cuts the theory loose
from just those aspects of behavior that we wish to predict. No
one desires this sort of solution. Furthermore, such an approach
indirectly would admit that there are unknown variables, other
than rewards, that can build up resistance to extinction. These
other variables would have to be seen as even more potent than
rewards because no accumulation of rewarded experiences ever
makes a 100 per cent reward group as resistant to extinction as
a partially rewarded one.

Attempted Explanations

The contradiction between learning theory and data has
stimulated many people to try to find some explanation. These
explanations have centered, almost exclusively, on the data con-
cerning partial reward. The reason for this exclusive focus is
historically simple. The partial reward effect was the first one
to be noted, whereas the data concerning the effect of delay of
reward are relatively recent. The role that effort has in increas-
ing resistance to extinction has been largely overlooked in spite
of the data in the literature.

The task for those who have attempted to explain these ap-
parent contradictions has not been an easy one. The explana-
tions that have been offered represented great theoretical inge-
nuity and were, on the whole, adequate to explain what was
known at the time. Like all good explanations, they stimulated
further research. Unfortunately, this further research tended
to make them less tenable. Nonetheless, it is because of these
explanations that there is now sufficient data to permit new ex-
planations. We shall review the past critically for the purpose
of providing a background for the explanation we wish to offer.

Attempts to explain the partial reward effect have been so
numerous that it is not feasible to review all of them. We shall
review, and attempt to evaluate, those that have seemed most
plausible and have gained at least temporary acceptance. We
shall concentrate on those that have led to current formulations
and, of course, on those that are still current.

14 AN IMPASSE FOR LEABNING THEORY

The Humphreys Hypothesis. -One of the earliest explana-
tions of the partial reward effect was suggested by Humphreys
( 1939 ) . In an experiment using human eye-blink conditioning,
Humphreys demonstrated clearly that resistance to extinction
was greater after a sequence in which, on some occasions, the
conditioned stimulus was not followed by a puff of air to the
eye than after a sequence in which the puff always followed the
conditioned stimulus. To account for this he offered an explana-
tion that has provided the basis for much of the subsequent
theorizing about the effects of partial reward.

According to Humphreys, the subject continues to respond
until he has had sufficient experience with the conditions during
extinction to convince himself that the reinforcing event no
longer occurs in this situation. This explanation can account
for the difference in resistance to extinction between a 100 per
cent rewarded group and a partially rewarded one. A given
reward is present on every training trial for the 100 per cent
group, and then it is suddenly removed when extinction trials
begin. This sharp and sudden change of stimulus conditions
permits these subjects to realize quickly that there has been a
change. For the partially rewarded subjects, however, there is
less change in the stimulus conditions between the training trials
and the extinction trials. During the training trials the subjects
frequently experience omission of reward, and therefore extinc-
tion trials do not represent a totally new situation for these indi-
viduals. This overlap in stimulus conditions makes it difficult
for them to discriminate between the end of training and the
beginning of extinction. This greater difficulty of discrimination
reveals itself as a slower rate of extinction.

There are really two aspects to this explanation of extinction
effects that Humphreys has offered. Although they are similar
in nature, it is advantageous to discuss them separately. One
of these aspects we should like to call an "amount of information
explanation." The other has been called a "discrimination ex-
planation." The former says that extinction occurs only when
the subject has had sufficient experience to expect consistent
absence of reward. Subjects trained on a partial reward sched-
ule have come to expect a certain number of unrewarded trials

AN IMPASSE FOR LEARNING THEORY 15

mixed in with rewarded ones; consequently, when extinction
starts, it takes them longer to realize that reward is totally absent
than it takes subjects that have been always rewarded. If sub-
jects are trained with a very low ratio of rewarded to unre-
warded trials, extinction may take very long indeed.

This explanation, although somewhat vague, and certainly
not well integrated with conventional learning theory, does ex-
plain the major data on the partial reward effect. It does not,
of course, explain the increased resistance to extinction follow-
ing delay of reward, nor does it explain the fact that increased
effort increases resistance to extinction. But these latter facts
were not known at the time when Humphreys offered his ex-
planation. So far as data relating to the effects of partial reward
are concerned, this "information" hypothesis has never been in-
validated. Its lack of general acceptance among learning theo-
rists may be due to a number of things. First of all, it is difficult
to integrate this idea into learning theory in any precise manner.
Second, there is undoubtedly some suspicion that the magnitude
of the effects obtained in experiments is not fully consistent with
this explanation. We shall leave it at this for now, although
later in this book we shall present new data on the basis of which
we may discard this "information explanation."

The second aspect of the explanation offered by Humphreys
has been much more widely accepted. This "discrimination ex-
planation" focuses on the fact that there are more elements in
the situation that are common to both extinction and acquisition
for partially rewarded than for continuously rewarded subjects.
This is true whether one is dealing with eye-blink conditioning
or with a hungry animal running an alley. The common element
for the partially rewarded animal is the presence of non-re-
warded trials both during training and during extinction, an
overlap that is not experienced by the continuously rewarded
one. It has long been known that an animal finds it more difficult
to establish a discrimination between two stimulus situations
that differ in only a few aspects than between two that differ
in many. Consequently, if the partially rewarded animal learns
to respond on unrewarded trials during training, it is not at all
surprising that it transfers this responding to the extinction situ-

16 AN IMPASSE FOR LEARNING THEORY

ation to a far greater extent than does the continuously rewarded
one that has never learned to respond on such trials. This "dis-
crimination hypothesis" has been taken over in one form or
another by many other theorists (Bitterman et al, 1953; Mow-
rer, 1960).

If one examines this explanation closely, however, it turns
out that it does not really relate the partial reward effect to an
organized set of theoretical concepts. Actually, it is mainly an
extension of an empirical generalization. We have observed in
a variety of conventional discrimination experiments that the
greater the similarity of the stimuli in two situations the harder
it is for an animal to establish differential responses to those
situations. We then observe that there is at least one sense in
which the training and extinction conditions for the partially
rewarded animal are more similar than they are for the con-
tinuously rewarded animal. From this we infer that the partially
rewarded animal wfll have more difficulty in establishing differ-
ential behaviors, those of responding and not responding, in
the two conditions.

There is nothing wrong in the use of such empirical generali-
zations. Often they are the only basis for prediction that we
have. The great difficulty is that there are always gross excep-
tions to the rule which we tend to gloss over. An example with
respect to the present generalization arises in the case of delay
of reward. Wike and McNamara (1957) did a study which
differed in design from the conventional one involving delay of
reward. Their apparatus consisted of a runway leading into a
delay compartment, which in turn exited into a goal box. The
control animals ran directly through the delay compartment and
immediately found food in the goal box. The experimental ani-
mals were trapped for a few seconds in the delay compartment,
and then released to find food immediately in the goal box.
During extinction both groups were permitted to run directly
through the delay compartment into the goal box, but of course
there was no longer any food.

If we ask what the similarities are between training and ex-
tinction conditions, it is clear that the two conditions are more
similar for the control than for the delay group. The control

AN IMPASSE FOR LEARNING THEORY 17

group always ran directly through the delay compartment in
both training and extinction conditions. The delay group, on
the other hand, had been retained there during training, but
not in extinction. Clearly, this switch from delay to no delay is
an abrupt change in conditions for the latter. So, in terms of
our empirical generalization, we have every right to expect that
the delay animals will extinguish more rapidly than the control
ones. But this is not what happens; instead, just the converse
is true.

Strong believers in the "discrimination hypothesis'* may not
appreciate this exception to their generalization, even though
in terms of "obvious" similarities the argument is impeccable.
They will point to other possible similarities, such as the fact
that the delay animals have experienced delay without food at
least some place in the apparatus during training, whereas the
control animals have not. This experience of not obtaining food,
it may be argued, is the characteristic common to the training
and extinction situations for the delay animals that is important
in increasing resistance to extinction.

This counterargument, however, reveals the weakness of an
empirical generalization as compared with a true theoretical
explanation. There are always a multitude of similarities and
differences between training and extinction conditions for both
experimental and control animals. Consequently, depending
upon which ones are picked and how they are weighted, a va-
riety of predictions about extinction can be made. It is only
when an empirical generalization of this sort can be related to
an organized set of theoretical concepts that one has a criterion
by means of which such a selection can be made. There have
been many serious attempts to provide the needed theoretical
basis for the discrimination hypothesis. We shall proceed to
examine some of them.

The Sheffield Hypothesis. One of the most ingenious and
coherent theoretical bases for the discrimination hypothesis was
proposed by Sheffield ( 1949 ) . Her line of reasoning was cogent
and plausible. It seems reasonable to postulate that reward and
non-reward produce distinctive reactions in the animal, which
in turn produce distinctive internal stimuli. The act of eating

18 AN IMPASSE FOR LEARNING THEORY

undoubtedly produces characteristic kinesthetic stimuli. The
reaction to non-reward undoubtedly produces a very different
but equally characteristic set of stimuli. It is also quite reason-
able to assume that these characteristic internal stimuli, the
aftereffects of rewarded or unrewarded trials, persist for a period
of time.

With these assumptions in mind, Sheffield gave the follow-
ing theoretical analysis of the training experiences of animals
rewarded 100 per cent of the time and of partially rewarded
animals. If animals are rewarded on every trial, they always
have those stimulus aftereffects that are characteristic of eating.
If these aftereffects persist until the following trial, they form
part of the stimulus complex that is present when the animal
again runs in the apparatus and is again rewarded. Conse-
quently, the stimulus aftereffects of eating become associated
with the running response. Partially rewarded animals, on the
other hand, sometimes have stimulus aftereffects characteristic
of reward and sometimes have those that are characteristic of
non-reward. In so far as these persist from one trial to the fol-
lowing trial, each is sometimes present when the animal again
runs and is rewarded. Consequently, both types of stimulus
aftereffects become associated with the running response. Thus,
in contrast to the continuously rewarded animal, the partially
rewarded one has established two associations namely, running
in the presence of reward aftereffects and running in the pres-
ence of non-reward aftereffects.

During extinction all animals experience only the stimulus
aftereffects characteristic of non-reward. These have never been
associated with running for the continuously rewarded animals.
Thus, in terms of the concept of stimulus generalization, there
should be a decrement in the strength of the running response for
these animals, and they should extinguish rapidly. On the other
hand, the aftereffects of non-reward have been associated with
running during the training of the partially rewarded animals.
There is, then, little stimulus generalization decrement when
extinction trials begin, and they should extinguish more slowly.
Thus, a coherent theoretical account of partial reward effects
was given by postulating that rewards and non-rewards produce
stimulus events that persist until the start of the next trial.

AN IMPASSE FOR LEARNING THEORY 19

The crucial assumption here concerns the persistence of
these aftereffects. For both theoretical and empirical reasons,
theorists have agreed that these stimulus traces are short lived,
that is, they disappear within minutes or even seconds. Incor-
porating this knowledge concerning the durability of stimulus
traces into the theoretical explanation leads to the conclusion
that partial reward effects should be observed only under
massed training and massed extinction conditions and should
not be found when the trials are widely spaced. If spaced trials
are used during training, animals that are always rewarded and
animals that are partially rewarded would not have any differ-
ential stimulus traces to be associated with the running response
because the stimulus aftereffects of the preceding trial would
have disappeared. Thus, with widely spaced trials the partial
reward effect should disappear or perhaps even be reversed.

Realizing that this derivation concerning the effects of
spaced and massed trials was crucial for the explanation, Shef-
field conducted an experiment to test its validity. She found that
when animals were trained under conditions of massed trials ( an
intertrial interval of about fifteen seconds ) the usual difference
between partially rewarded and 100 per cent rewarded animals
appeared. If, however, the animals were trained using spaced
trials ( an intertrial interval of fifteen to twenty minutes ) there
was no significant difference between the two groups in resist-
ance to extinction.

These data, of course, gave strong support to the Sheffield
explanation. If these results could be replicated, and if the Shef-
field explanation could be accepted as correct, there would no
longer be any contradiction at all between learning theory and
the data concerning extinction after partial reward. There were,
consequently, a number of attempts to repeat the Sheffield ex-
periment. Unfortunately, the results she obtained did not stand
up. We shall review some of these studies in order to give a
fair picture of the evidence that has accumulated.

Two experiments directly attempted to replicate the Shef-
field finding. Lewis (1956) did one of these studies using an
apparatus and procedure almost identical to that used by Shef-
field. The major difference between the Sheffield and the Lewis
experiments was the time intervals between trials. Both experi-

20 AN IMPASSE FOR LEARNING THEORY

ments used a fifteen-second intertrial interval for massed train-
ing, but whereas Sheffield used a fifteen-minute interval for the
spaced trials, Lewis used only a two-minute interval. Lewis
found that the intertrial interval made no difference. The par-
tially rewarded animals extinguished more slowly than those
that were rewarded on every trial, regardless of the intertrial
interval.

Wilson, Weiss, and Amsel (1955) replicated the Sheffield
experiment using no procedural variations whatsoever. They
used the same kind of apparatus, the same procedure, and the
same time intervals that Sheffield had used. They also found
that the intertrial interval, that is, whether the training trials
were massed or spaced, made no difference at all. Regardless of
the intertrial interval, the partially rewarded animals showed
themselves to be more resistant to extinction than those that had
been rewarded 100 per cent of the time during training. These
failures to replicate the Sheffield result suggest that her finding
may have been due to sampling error.

The final blow to the Sheffield hypothesis as an adequate
explanation of partial reward effects was given by the Weinstock
experiment to which we have previously referred. When he
demonstrated that clear-cut effects of partial reward on extinc-
tion were obtained even though training trials were spaced
twenty-four hours apart, it no longer was possible to believe in
a hypothesis that made the intertrial interval the crucial vari-
able.

We have reviewed only a few of the many studies that have
been done in the last ten years. An examination of all the re-
search leads Lewis to say: "The conclusion seems to be rather
firm that the PRE [partial reward effect] obtains whatever the
spacing of the acquisition trials." (Lewis, 1960, p. 10.) One
must conclude that the Sheffield interpretation must be dis-
carded as an explanation for the effects of partial reward.

"Competing Response 9 Hypotheses. Several theorists have
offered explanations of the partial reward effect that circumvent
the need for having stimulus traces persist between trials. Some
of these theories are based on the idea that unrewarded trials
produce competing responses which are either adapted out or

AN IMPASSE FOR LEARNING THEORY 21

conditioned to miming on subsequent rewarded trials. Wein-
stock (1954) has emphasized the adaptation to non-reward.
Estes (1959) has emphasized the other possibility. We shall
base our discussion here mainly on the statement by Estes,
which represents a more complete theoretical account. Estes
says:

According to the present theory, the mechanism for extinction of an in-
strumental response is conceived as follows. The function of non-reinforce-
ment is to establish a stimulating situation in which competing responses
have high probabilities. When the competing responses are evoked in the
presence of stimulus elements which are connected to the formerly rein-
forced response, conditioning occurs in accordance with the contiguity
principle, and the competing responses gain connections at the expense of
the formerly reinforced one. During a series of reinforced trials, some one
response, e.g., approaching a food tray, becomes well conditioned to the
reinforcing situation, e.g., the goal box of a maze. Then when reinforce-
ment is first omitted, cues from the changed situation and cues arising from
the disrupted response sequence evoke competing responses with high
probability. Consequently, extinction tends to be rapid following a series
of continuously reinforced trials. Under a partial reinforcement schedule,
the situation is somewhat different. Competing responses which become
conditioned following a non-reinforcement early in the series will tend to
occur on later reinforced trials; therefore, response-produced stimuli asso-
ciated with them will become conditioned cues for the reinforced response
and will tend to maintain the latter during a subsequent extinction series.
(P. 437.)

In brief, the idea is that an unrewarded trial tends to evoke
responses in the animal that compete with the response of run-
ning to the goal box. As a result of the mixture of rewarded and
unrewarded trials, the partially rewarded animal will make
these competing responses occasionally on a rewarded trial.
Thus, because these competing responses are followed by run-
ning to the goal box and being rewarded, the stimuli produced
by these competing responses become additional cues for run-
ning to the goal box. Presumably, this does not happen to an
animal that was rewarded 100 per cent of the time, because it
rarely, if ever, makes any competing responses during the train-
ing trials. For a partially rewarded animal, therefore, many
stimuli that normally would lead to competing behavior, and
hence would hasten extinction, have become cues for eliciting
the running response. This has not happened for the animal

22 AN IMPASSE FOR LEARNING THEORY

that was always rewarded. For this reason, the partially re-
warded animal persists longer during extinction trials than does
the animal that was trained on a schedule of 100 per cent
reward.

This hypothesis seems plausible, but it is rather difficult to
evaluate. The source of the difficulty is the lack of specification
of a number of rather important points in the hypothesis, with-
out which the hypothesis cannot be tested empirically. Estes
(1959) himself admits that application of this theoretical ex-
planation to experimental data on extinction "suffers ambiguity
because there are no general rules for prescribing just what re-
sponses will 'compete' with a given response" (p. 437, note).
There are also other vaguenesses and unclarities. There is no
specification of any variables that would raise or lower the
probability of evoking competing responses during training, and
there is no specification of where in the apparatus these compet-
ing responses must be evoked in order to produce the increased
resistance to extinction.

Let us examine an experiment by Katz (1957) that seems
relevant to this explanation. Katz trained rats on two runways
simultaneously. These runways were of equal length but other-
wise quite distinguishable. Training continued for 10 days, with
runs on Alley I and Alley II alternating on each day. The time
interval between an animal's run on Alley I and its succeeding
run on Alley II was 20 seconds. There was, on the other hand,
a 15-minute interval between an animal's run on Alley II and
its next run on Alley I. All animals were given 74 acquisition
trials on each of the two alleys, and then all were extinguished
only on Alley II. Three different conditions of training were
employed: (1) One group of animals was rewarded on every
trial in both alleys. We shall refer to this as the "100 per cent
reward condition." (2) A second group received partial reward
(50 per cent) on Alley I, but on the alley used for extinction
(Alley II) this group also received 100 per cent reward. We
shall refer to this group as the "partial-100 per cent reward con-
dition." (3) The third group received 100 per cent reward on
Alley I, but on the alley used for extinction (Alley II ) this group
received 50 per cent reward. To emphasize the experience on

AN IMPASSE FOR LEARNING THEORY 23

the alley used during extinction, we shall refer to this group as
the "partial reward condition."

Katz's purpose was to assess the general importance of inter-
trial versus intratrial effects on resistance to extinction. If inter-
trial effects are important, then the "partial-100 per cent" group
should show the greatest resistance to extinction. For these
animals, any unrewarded trial on Alley I was immediately fol-
lowed by a rewarded trial on Alley II. This arrangement should
maximize the possibility that the "partial-100 per cent" group
was running to rewards when dominated by the aftereffects of
non-reward. On the other hand, what would be expected if
increased resistance to extinction in partial reward situations
results from intratrial effects, that is, effects occurring specifi-
cally on the unrewarded trials? The "partial reward" group was
the only one that experienced partial reward on the alley on
which extinction trials were run. Hence, if increased resistance
to extinction results from something that happens during the
unrewarded trial, and independently of the carryover of the
aftereffect of an unrewarded to a succeeding rewarded trial, the
"partial reward" group should be more resistant to extinction.
The results of this experiment are clear. They show that the
"partial reward" group is significantly more resistant to extinc-
tion than either of the other two. Thus, Katz concludes that
intratrial, rather than intertrial, processes are primarily involved
in partial reward effects. What implications exist here for the
competing response hypothesis?

Let us make some reasonable specifications of the Estes hy-
pothesis with respect to this experiment. Consider the "partial-
100 per cent" group that was partially rewarded on Alley I and
always rewarded on Alley II. It seems reasonable to assume
that these animals would be very likely to make competing re-
sponses when run in Alley II. After all, every unrewarded trial
in Alley I is immediately followed by a trial in Alley II. Thus,
if the occurrence of an unrewarded trial increases the likelihood
of competing responses on the very next trial, the training se-
quence for the "partial-100 per cent" group has maximized com-
peting responses in Alley II. Also, one can be certain that every
time a competing response does occur in Alley II it is followed

24 AN IMPASSE FOR LEARNING THEORY

by reward since these animals are always rewarded in Alley II.
Undoubtedly the animals make a discrimination between the
two alleys, but it seems reasonable to suppose that there is suffi-
cient generalization between them to keep the probability of
competing responses in Alley II fairly high.

What would one expect from the "partial reward" group that
was always rewarded in Alley I and partially rewarded in Alley
II? Here again, of course, one would expect competing re-
sponses to occur in Alley II. It must be remembered, however,
that immediately preceding any trial in Alley II these animals
experienced a rewarded trial in Alley I. Consequently, it is rea-
sonable to assume that the probability of such competing re-
sponses would not be too high. In addition, even when compet-
ing responses did occur in Alley II, they did not always occur
on rewarded trials, since only half of the trials in Alley II were
rewarded for this group.

If the above analysis is reasonable, what would one expect
concerning differences in the resistance to extinction between
these two groups? If one emphasizes the effect of the imme-
diately preceding trial, one would come to the conclusion that
the "partial-100 per cent" group should be somewhat more re-
sistant to extinction. If one emphasizes the discrimination that
the animal probably develops between the two alleys, one
would conclude that those that were partially rewarded in Alley
II should be somewhat more resistant to extinction. With these
two factors working in opposite directions, any reasonable ap-
plication of the Estes explanation does not lead one to expect
any great difference between these two groups.

The data, however, show a very large difference between
these two conditions. Those animals that were partially re-
warded on Alley II are very much more resistant to extinction
than those partially rewarded on Alley I. Indeed, the latter
group is only slightly more resistant to extinction than were the
animals that had received 100 per cent reward on both alleys.
Thus, if our specifications are reasonable, the data do not sup-
port the competing response interpretation. Some readers might
argue against the reasonableness of the specifications we have
made in trying to apply this interpretation to experimental data.
All we can say is that these specifications seem reasonable to us.

AN IMPASSE FOR LEARNING THEORY 25

Clearly, we have not refuted the existing explanations based
upon the concept of competing responses. All we have done is
to point to some difficulties in evaluating these explanations.
Later in this book we shall return to this problem in connection
with some new data that seem directly pertinent.

The Logan Hypothesis. It is quite possible that an unre-
warded trial has psychological effects other than the kind em-
phasized by Sheffield and by Weinstock. For instance, such a
trial might change the motivational state of the animal, and this
in turn might well produce differences in performance between
continuously and partially rewarded animals.

Logan (1960) has attempted to account for the effect of
partial rewards along such motivational lines. His account also
has the advantage of explicitly dealing with the effects of both
partial reward and delay of reward on resistance to extinction.
Logan tends to think of the two as being on the same continuum.
An unrewarded trial on a partial schedule is, to him, an infinite
delay of reward. Consequently, the same explanation should
hold for both.

Logan assumes that, when an animal runs and finds food in
the goal box, it makes a characteristic set of goal reactions-
chewing movements and the like. These goal reactions become
anticipatory on later trials. The animal begins to make them as
soon as it is placed in the start box. For Logan, it is the arousal
of these that provides "incentive motivation." To account for
the rapid extinction of continuously rewarded animals, he as-
sumes that when these animals first find an empty goal box, the
stimuli present still tend to evoke these goal reactions. During
extinction, however, these reactions weaken because they are
never followed by reward. It is the extinction of these anticipa-
tory goal reactions, and thus the decrease in the accompany-
ing "incentive motivation/* that causes the animal to run more
slowly on successive extinction trials.

Logan then accounts for the effect of partial reward and
delay of reward on resistance to extinction in the following way.
He argues that under these training procedures, the animal has
frequent experiences of running into the goal box when food
is absent. Gradually, the animal builds up a discrimination
that inhibits the tendency to make goal responses when the food

26 AN IMPASSE FOR LEARNING THEORY

is absent. On extinction trials, such an animal has very little
tendency to make these goal reactions to the empty goal box.
Consequently, these anticipatory goal reactions and the accom-
panying incentive motivation extinguish very slowly.

In many ways this explanation is very similar to the sug-
gestion made by Mowrer ( 1960) concerning adaptation to frus-
tration effects. However, Logan's greater specification of his
explanation makes it possible to attempt an evaluation of his
hypothesis. His account of the effects of delay of reward im-
plicitly assumes that the delay takes place in the goal box. It is
the empty goal cup that must become the cue for inhibiting the
anticipatory goal responses, and the full one the cue for evoking
them. Only if the animal has repeatedly experienced both of
these situations can it establish a discrimination of the type
postulated. But as was pointed out previously ( cf. Wike and
McNamara, 1957), there have been studies on delay of reward
in which the delay occurred in a special compartment prior to
the animal's entrance into the goal box. Once these animals en-
tered the goal box, food was immediately present. Clearly this
is a situation in which all the cues in the goal box should become
conditioned to eliciting the goal reactions in both the delayed
and non-delayed groups. There is no occasion for the delayed
animals to learn to inhibit these reactions to the stimulus of an
empty food dish because they never experience this condition
during training. Nonetheless, when extinction is run directly
to the goal box with no further delay for either group, the delay
of reward effect on resistance to extinction is still present. This
result is clearly at variance with what Logan's hypothesis would
predict.

Obviously, one such contradiction is not sufficient to justify
ignoring this explanation, especially when it is so far the only
one that seemingly integrates the data from both partial reward
and delay of reward studies. We believe,, however, that much
of the data we shall present in the following chapters would be
difficult to account for using Logan's concepts.

The Amsel Hypothesis. A different motivational approach
to the problem of partial reward effects is based on the work of
Amsel ( 1958 ) . Many of the concepts involved were anticipated

AN IMPASSE FOR LEARNING THEORY 27

by Spence ( I960, pp. 97 ff . ) . Amsel, however, was the first to
develop the ideas sufficiently so that they could apply to the
effects of partial reward on resistance to extinction.

His explanation rests on the notion of a frustration drive. The
presence of this drive may be inferred from the behavior of ani-
mals in an apparatus consisting of an initial runway leading to
a mid-box and a second runway leading from the mid-box to
an end box. Animals were run in this apparatus with a food
reward in the mid-box on only a fraction of the trials, but with
a reward in the end box on every trial. On unrewarded trials in
the mid-box, the animals were delayed for a period of time be-
fore being released to run the second alley. The main finding
was that the running speed in the second alley was greater after
unrewarded mid-box experiences than after rewarded ones.
Amsel's interpretation assumes that the experience of non-re-
ward produces a specific but implicit response, the frustration
response, which in turn gives rise to a specific pattern of stimu-
lation as well as to the motivational state of frustration. This
frustration drive is capable of energizing any habit the animal
has learned, such as that of running the second alley. Thus, on
unrewarded mid-box trials, according to this hypothesis, the
animals have a stronger drive state when they run the second
alley than they have on rewarded trials.

Amsel uses these concepts in interpreting the partial reward
effect as follows. He considers the frustration response to be
aroused on each unrewarded trial the animal experiences. In-
itially, it is aroused only in the goal box where the animal has
learned to expect food. But, like other responses, it can become
anticipatory, that is, it can be evoked by stimuli that occur prior
to the goal box, such as those in the runway and start box of the
apparatus. When this frustration response is aroused, it pro-
duces its own specific stimulus pattern. Since this stimulus pat-
tern is present when the animal runs, it becomes associated with
this overt behavior and, thus, eventually becomes one of the
cues for running. It should be noted that this partially rewarded
animal also has a higher drive level than a continuously re-
warded animal because of the motivational consequences of this
frustration response.

28 AN IMPASSE FOR LEARNING THEORY

As we understand the Amsel hypothesis concerning extinc-
tion, animals trained under 100 per cent reward, and then placed
on extinction, have this frustration response aroused for the first
time. As it becomes anticipatory, two things occur: (1) because
the stimulus pattern characteristic of the frustration response
has never been associated with the act of running forward, its
presence during extinction tends to arouse competing behaviors
that hasten extinction; (2) at the same time, the increase in
drive level tends to be channeled into these dominant, compet-
ing behaviors and thus also hastens the extinction process. On
the other hand, partially rewarded animals did continue to run
during training trials in spite of occasional unrewarded trials.
This permitted the stimulus pattern characteristic of the frus-
tration response to become associated with running. Conse-
quently, when these same stimuli occur during extinction trials,
they tend to elicit the running response rather than competing
behaviors. This in itself tends to increase resistance to extinc-
tion. At the same time, the frustration drive should help main-
tain the running behavior.

To the extent that one considers the stimulus functions of
this frustration response, the resulting explanation of partial re-
ward effects is not much different from that based on competing
responses. Both emphasize that the greater resistance to extinc-
tion shown by partially rewarded animals stems from the fact
that they have been trained to run to stimuli that are also char-
acteristic of the extinction situation. However, Amsel also in-
vokes a motivational principle to augment the effects attribut-
able to the association between the frustration stimuli and the
running behavior. In this respect there is a similarity to the
Logan hypothesis. An evaluation of the adequacy of the Amsel
hypothesis in accounting for partial and delayed reward effects
is difficult at present because of the paucity of relevant experi-
ments. We shall attempt such an evaluation in later chapters
in terms of our own research findings.

In this brief review, we have been unable to do justice to all
the ingenuity that has been displayed in attempts to account for
partial reward and delay of reward effects. It should be clear,
however, that there is a great family resemblance among many

AN IMPASSE FOR LEARNING THEORY 29

of the explanations that can be traced back to the discrimination
hypothesis. Most of them postulate a greater stimulus similarity
between the training and extinction situations for the partially
rewarded animal than for the continuously rewarded one. As
a consequence, the partially rewarded animal during training
forms an association between those stimuli characteristic of the
extinction situation and the response of running. This associa-
tion does not occur for the continuously rewarded ahiinal, and
since, it does not, the former continues to run during extinction
whereas the latter faces a somewhat new and novel stimulus
situation that disrupts its performance. The major shift in these
accounts over the years has been from an emphasis on intertrial
sources of stimulation, as in the Sheffield account, to a reliance
on intratrial factors such as frustration responses and competing
behaviors.

The one new and stimulating approach to the explanation
of partial reward effects has been the introduction of motiva-
tional in addition to associational concepts. Our own solution
to this theoretical problem, which we shall outline in Chapter 2,
also emphasizes the role of motivation. The nature of the moti-
vational concepts we suggest, as well as the manner of their
operation in increasing resistance to extinction, is, however,
quite different from that suggested by either Logan or Amsel.

Dissonance Reduction Effects
in Learning Situations

In Chapter 1 we considered the difficulties that learning theory
is having at present with a large body of empirical data. Let us
briefly review the problem posed by the data:

1. Although rewards are supposed to strengthen a habit, one
finds that habits that have been partially rewarded are more
resistant to extinction than those that have been continuously
rewarded.

2. Although temporal delay between performing a response
and obtaining a reward is supposed to weaken a habit, one finds
that habits that have been acquired with delayed reward are
more resistant to extinction than those acquired without delay.

3. Although expenditure of effort in the performance of a
response is supposed to build up inhibition and thus weaken the
habit, one finds that habits acquired under conditions requiring
considerable effort are more resistant to extinction than those
acquired with little expenditure of effort.

We have discussed the inadequacies ofihe attempts to rec-
oncile this conflict between learning theory and data. In this
chapter we shall propose an explanation that we feel is more
adequate. We shall begin our presentation by regarding the
data from a purely empirical point of view. The reason for doing
this is to find some unifying theme running through this diversity
of data. If we can do this, we will be closer to finding a theoreti-
cal explanation.

DISSONANCE REDUCTION EFFECTS 31

An Empirical Generalization

If one searches for factors common to the three variables of
partial reward, delay of reward, and effort, one is impressed by
one obvious similarity. This similarity is readily apparent when
we consider the animal's reactions in a free choice situation. If
an animal is given a choice between an alternative that provides
100 per cent reward and one that provides partial reward, it
chooses the 100 per cent rewarded alternative; if given a choice
between an alternative where reward is immediate and one
where it is delayed, it chooses the immediately rewarded alter-
native; and if given a choice between two alternative paths to
the same goal which differ only in the amount of work required,
it chooses the least effortful path. Clearly each of these three

*- " ln "**^,,' ,_ ..-Ml. ' ./--- r,~,-^ 1 f-l-t f

variablespartial reward^delay of jreward, and efiort-r-is some-
thing the animal will avoid if given an opportunity tojdto. so,.
This contention is easy to support with experimental evidence.

1. Partial reward. Branswik (1939) reports an experiment
in which rats were given a series of learning trials in a T-maze.
One arm led to a goal box in which food was always available.
The other arm led to a similar goal box in which food was avail-
able on only 50 per cent of the trials. The animals quickly learned
to go to the side offering 100 per cent rewards significantly more
often than chance would allow. When the reward percentages
in the two goal boxes were reversed, the animals quickly re-
versed their behavior. Clearly, animals would rather go to a
place where they are always rewarded than to one where they
are rewarded only occasionally.

2. Delay of reward. Logan (1952) reports an experiment
in which rats were given a choice between two alternatives, both
of which led to an equal reward on each trial. For one alterna-
tive, the reward appeared one second after the choice was made.
If the other alternative was chosen, however, the animal had to
wait five seconds before the reward was presented. The data
show that the animals quickly learned to choose the alternative
that yielded the more immediate rewardthey went almost 100
per cent of the time to the alternative where food was presented

32 DISSONANCE REDUCTION EFFECTS

after only one second. Furthermore, if after they had learned
this, the delay intervals were reversed between the two alterna-
tives, the animals quickly changed their choice. In short, they
clearly preferred an immediate to a delayed reward.

3. Work or effort Numerous studies have shown that rats
will choose the shorter of two paths to a goal box. It is not easy,
however, to find studies in which the variable of effort is not
confounded with other variables, such as the time elapsing be-
tween the choice point and the reward. Fortunately, Thompson
(1944) reports one experiment in which the alternatives avail-
able to the animal did differ only in the amount of effort re-
quired. This was achieved by providing a lever that the animal
had to press in order to gain access to the reward. One lever re-
quired a pressure of forty grams, the other of sixty grams. When
given free choice trials, the animals soon learned to choose the
low effort alternative on practically every trial, thus showing a
marked preference for the less effortful alternative.

Considering these facts about free choice behavior in con-
junction with what we already know about resistance to extinc-
tion, we can state an empirical generalization of broad scope:
The set of conditions that an animal chooses least often in a free
choice situation will result in increased resistance to extinction,
in a non-choice situation, if the animal has experienced them
during acquisition. In other words, consider two values of any
variable for example, a long and a short delay of reward.
Assume that, in a free choice situation, the animal consistently
chooses one in preference to the other when all other things in
the situation are equal. This variable, then, should make a dif-
ference in resistance to extinction for animals trained in a non-
choice situation such as a simple runway. A group that experi-
ences the less preferred value of the variable during training
will be more resistant to extinction.

Later we shall have to qualify this generalization, but for
the moment let us accept its correctness as stated. The accept-
ance of this generalization permits us to restate the problem
which requires theoretical explanation. We need no longer be
concerned with the specificities of partial reward, delay of re-
ward, or effort. Rather, the problem to be explained may be

DISSONANCE KEDUCTION EFFECTS 33

stated as follows: Why does an animal that has been induced to
experience repeatedly a less preferred situation show increased
resistance to extinction?

Overview of Dissonance Theory

Stating the problem in this manner suggests that we might
find a solution to it by turning to a theory that was developed
to account for similar phenomena in humans. This is the the-
ory of cognitive dissonance, initially formulated by Festinger
(1957). The theory, in part, deals with situations in which an
individual's actions are not entirely consistent with what he
knows about the environment. An animal that suffers, say, de-
lay of reward but still continues to run is in a situation where it
knows things that are inconsistent with its actions. Since there
is some similarity here, perhaps the theory of dissonance can
offer an adequate explanation of our empirical generalization.
We shall first present a brief, intuitive sketch of the theory as
it applies to humans. We shall then develop its implications
more rigorously as it applies to resistance to extinction in non-
verbal animals.

The theory of cognitive dissonance deals, in part, with the
psychological states that arise in humans as a result of taking
some action and then finding that the consequences of this act
are not sufficient to justify the action takei|. Such conditions set,
up a motivational state called dissonance. Illustrations of situ-
ations that might establish dissonance are easy to come by. For
instance, there is the new and eager Ph.D. who decides to accept
a position at Jones College. After arriving with bag and bag-
gage for the fall term, he finds that the college is very inferior
intellectually, socially, and financially. Or again there is the
conscientious saver who, after extensive house hunting, buys
one and then finds it is riddled by termites, has a leaky roof,
and needs new plumbing. In both of these situations dissonance
exists. The basis for this dissonance is the opposition between
two cognitions., or two sets, of inf ormation, the individual has.
Lf the latter example, the information that he has purchased the
house is dissonant with the information he has about undesir-
able aspects of the house. Considering only things like its ter-

34 DISSONANCE SEDUCTION EFFECTS

mites and its plumbing, he would not ordinarily have under-
taken this action. More generally, dissonance exists between
two pieces of information if the obverse of one would normally
follow from the other for that given individual

These states^ of dissonance^are^ said to have -motivational
properties .because they areiensional systems, that the individual
tends to reduce. Such reduction, however, can take place in only
one of two ways. The most common form of dissonance reduc-
tion is a change in behavior. If the homeowner were immedi-
ately to sell his house to someone else, his new behavior would
be consonant or compatible with his information about the un-
desirable aspects of its condition. However, it is frequently
impossible to reduce dissonance by such a change of behavior
because of social, financial, or other similar pressures. The home-
owner may well be stuck with his lemon. Under these condi-
tions, there is an alternative way in which the individual can
reduce the unpleasant state of dissonance, at least to some de-
gree. He can change his cognition or information about the
consequences of being the owner of the house. This can be done
in a variety of ways. By and large, however, they all involve
seeking additional information that is consonant with the act
of owning the house. He may convince himself that the splen-
did view, the excellent neighbors, and the nearness to schools
and shops more than compensate for the sad state of disrepair.
Or the consonant information he seeks may take even more
subtle forms-the "do-it-yourself" skills he must now acquire
are morally good as well as a benefit to one's health. The exact
form that this type of dissonance reduction will take is difficult
to specify, for it depends to such a large extent on the peculi-
arities of the individual and on the possibilities for finding such
dissonance-reducing information in a given situation.

An alternative way of stating this form of dissonance reduc-
tion is to say that the individual sets about discovering values
or rewards in the situation that satisfy some motivation he may
have other than the motivation that led him to take the action
in the first place. In buying a house, the individual was pri-
marily interested in providing an economical and comfortable
shelter for his family. With the arousal of dissonance, however,

DISSONANCE REDUCTION EFFECTS 35

the emphasis shifted to other motivations, such as those involved
in valuing neighborliness and the like. In the absence of dis-
sonance, these new values and rewards might not have been
sought or discovered. But once they have been discovered, they
partially reduce the dissonance by giving additional justification
for the action taken. At the same time they are now available
to influence future actions.

An example of this type of dissonance reduction in humans
is illustrated in an experiment by Aronson and Mills (1959).
The subjects in their study were college girls who volunteered
to join discussion groups. In one experimental condition the
girls were allowed to obtain membership in the group very
easily. In another condition they were subjected to a rather
painful and embarrassing selection procedure before they were
admitted. All subjects in both conditions had identical experi-
ences once they became members of the group. The results of
the experiment showed clearly that those subjects who had en-
dured unpleasantness in order to be admitted liked the group
better and thought the discussions more interesting than did
those who gained admission easily. In keeping with the theory,
those individuals who engaged in an action involving consider-
able unpleasantness found additional values in the situation that
were not apparent to others.

As applied to humans, this theory of cognitive dissonance
is not only plausible but is well documented by experimental
evidence. The question remains, however, whether it can be
formulated so as to apply to the behavior of a non-verbal animal
when it is confronted with partial reward, delayed reward, or
effort-evoking situations. We are assuming that these are un-
pleasant affairs and that when an animal voluntarily engages in
an action which involves them, a state of dissonance is aroused.
If this is true, the animal can reduce the dissonance by chang-
ing its behavior and refusing to repeat this action. If, however,
it is induced to continue in this activity (perhaps by being given
food when it is hungry), does the animal reduce its dissonance
by finding extra attractions in the situation? If it does, this
might well account for the increased resistance to extinction
that is shown under these training conditions. In light of what

36 DISSONANCE REDUCTION EFFECTS

we know about human behavior, this type of explanation has
considerable face validity. But a satisfactory test of the ade-
quacy of dissonance theory as an explanation for the empirical
generalization we stated previously is only possible if the impli-
cations of the theory are spelled out somewhat more rigorously.
This we shall do in the following section.

Definition of Dissonance

Let us specify three types of relationship that can exist be-
tween items of information. These are the following:

1. If A psychologically implies B, or B psychologically implies
A, then A and B are in a consonant relationship.

2. If A psychologically implies not-B, or B psychologically im-
plies not-A, then A and B are in a dissonant relationship.

3. If there is no psychological implication at all from A to B,
or from B to A, then A and B are in an irrelevant relationship.

We are, of course, making a number of assumptions about
the nature of these psychological implications. For instance,
we are assuming that, if A psychologically implies not-B, it
is impossible that B psychologically implies A.

Our main concern is with the second item above, the disso-
nant relationship. It also can be stated somewhat differently:
twojitems of information are in a dissonant relationship if, con-
sidering only these two items, the obverse of one follows psy-
chologically from tEe other. As an illustration, assume that a
rat has two items of information resulting from its actual ex-
perience. Item A is that it has just run the alley, and item B is
that no reward is present. Further, assume that if, at the begin-
ning of the trial, the rat had tlie information that no reward was
present (item B), this would psychologically imply for the rat
that it would not run the alley on that trial (not-A) . Thus item
B psychologically implies not-A, and the rat's information that it
has run the alley (item A) is therefore in a dissonant relation-
ship with the information that no reward is obtained (item B).

For the above definition of a dissonant relationship to have
precise meaning, it is necessary for us to specify exactly what is

DISSONANCE REDUCTION EFFECTS 37

meant by psychological implication. This is to be interpreted
as follows: if the acceptance of one item of information as true
sets up an expectation that some other item of information is
also true, then the first item psychologically implies the second.
Such psychological implication is, of course, different from logi-
cal implication. There are many bases other than logical reason-
ing for setting up expectations.

Similarly, we need to say something about our usage of the
term "item of information/' especially as it applies to non-verbal
organisms. Nothing very elaborate is intended. We assume that
the animal has information about an event, such as the presence
or absence of food, whenever that event can be shown to influ-
ence its behavior. With this usage, it is clear that it has informa-
tion both about the consequences of an act it has performed and
about the act itself. It is easy to show that its present behavior
is determined in part by the action it has just completed.

Such conceptual definitions concerning relationships be-
tween items of information, even if stated precisely, are not
useful unless one can relate them to the empirical world. We
must therefore face the problem of how to determine which
items of information have psychological implications for which
other items, and we must be able to do this for any given organ-
ism. In a like sense, we must be able to determine which items
of information an organism possesses at any given time. A com-
plete determination of this sort would, of course, demand an
operational method of measurement that would map out all the
items of information an organism possesses, and all of the inter-
relationships among these items. This we cannot give. We can
propose, however, operations that will do this for the kinds of
information with which we are here concerned. We are pri-
marily interested in only two types of information, that about
an action undertaken and that about its consequences.

To illustrate the problem concretely we shall choose, as an
example, the question of whether there is any psychological im-
plication, in one direction or the other, between the information
that a given course of action inevitably involves some unpleas-
antness and the information that an organism engages in this

38 DISSONANCE REDUCTION EFFECTS

behavior. We wish to emphasize, so as not to exaggerate the
importance of effort or unpleasantness in the reader's mind, that
absence of reward when the person has been oriented toward
it or delay of reward would be equally serviceable illustrations.

With a human subject, we could simply ask the following
question: "If the only thing you know about a given action is
that it involves pain and embarrassment, would you or would
you not engage in that action?" We can be reasonably certain
that our subject would tell us that he would not. Some subjects,
of course, would say that it would depend on other things such
as the rewards to be obtained and the possible alternatives.
But if we insisted upon knowing the expectation engendered
solely by the given piece of information, we would undoubtedly
obtain the answer we have suggested. From this we could con-
clude that for the specific person involved there was a psycho-
logical implication between the two items of information, and
we would know the direction of the implication. We would be
able to say that for this person the information that a given be-
havior involves pain is consonant with not engaging in the ac-
tion and is dissonant with engaging in it.

But how do we get an answer to this question, from a non-
verbal animal such as the white rat? Clearly, we must observe
its behavior and make some plausible inferences from this ob-
servation, For instance, we could give an animal a choice be-
tween two arms of a T-maze. If the animal turned right, it
would find food with no difficulty. If it turned left, it would
also find food but only after considerable difficulty and harass-
ment. Let us assume that, before being given this free choice,
the animal had considerable experience with both of the alter-
natives. Under these circumstances the animal undoubtedly
would choose the right turn, that is, the easy alternative. We
could then infer that for this animal, considering only the in-
formation that a given course of action leads to difficulty and
harassment, this psychologically implies that it does not engage
in that action.

Such an inference is almost justified, but not quite. It seems
justified when we are dealing with conditions that produce pain
or difficulty because our intuitive appraisal of the situation fits

DISSONANCE REDUCTION EFFECTS 39

with such an inference. Consider, however, a comparison that
might be made in the same apparatus between a small and a
large quantity of food. All other things being equal, a hungry
rat undoubtedly would choose the alternative that led to the
larger amount of food. In this case we would be unwilling to
infer that the information that a given action leads to a small
amount of food psychologically implies that the rat does not
engage in that action. Thus, the observation of such choices is
not sufficient for making this inference. Additional observations
are needed. In order to justify our inference we also need evi-
dence that the variable in question (harassment, food, etc.) is
a deterrent to action and not an incentive for it.

Suppose that a hungry animal is taught to run a simple
straight alley for food reward. After its running behavior has
become stabilized, we can introduce an increment of one of the
factors under consideration and observe its effects. If we intro-
duce an increment of delay, we have every right to expect that
this will slow up, if not prevent, the running behavior. In this
sense, delay is a deterrent to action. Indeed, any variable which,
when increased in magnitude, makes for decreased willingness
to perform an action, may be viewed as a deterrent. This type
of observation, in conjunction with the observation of choice
behavior, justifies the inference that the animal's information
that an action leads to some consequence such as delay psycho-
logically implies that it does not engage in that action. On the
other hand, if we add a small increment to the amount of food
in our runway situation there is no reason to expect that the
animal's willingness to run would decrease. Instead it would
probably increase. Thus, we can assert that even small incre-
ments of food are an incentive for action, certainly not a deter-
rent to it. Consequently, in spite of observations of choice be-
havior between large and small amounts of food, we cannot
infer that information that an action leads to a small quantity
of food psychologically implies for the animal that it does not
engage in that activity.

Thus, from these two types of observation we have usable
operational specification of when psychological implication
holds between information about an action and information

40 DISSONANCE SEDUCTION EFFECTS

about its consequences. We also can determine in this way
whether the relationship between the two items of information
is a consonant or a dissonant one. Expecting non-reward is con-
sonant with not running and dissonant with running. The con-
verse is true for an incentive factor such as food. There are, of
course, many variables that would have no influence on behavior
in either the choice or runway situations. In our terminology,
none of these would have psychological implication for the
action involved. Such variables bear an irrelevant relationship
to the behavior under consideration.

We now proceed to examine what we can say, according to
these conceptual and operational definitions, about experiences
of partial reward, delay of reward, and effort expenditure. Does
information that an action leads to any of the above conse-
quences psychologically imply that the animal does not engage
in that action? Earlier in this chapter we presented some evi-
dence that animals will choose 100 per cent reward rather than
partial reward, immediate reward rather than delayed reward,
and the less effortful rather than the more effortful action. The
remaining problem is to determine whether or not these are
also deterrents to action.

There is little or no problem in connection with delay of re-
ward. Experiments reported in the literature indicate that, as
the temporal interval between action and reward increases, the
animal performs more slowly (Logan, 1960), Consequently, we
can infer that information about enforced delay before obtain-
ing a reward is dissonant with engaging in the action.

In the case of effort or work, the evidence is also reasonably
clear cut. As effort is increased, performance becomes poorer
(Applezweig, 1951). Here, however, there is some slight am-
biguity. Changing the work requirements of a task frequently
changes the characteristics of the act that the animal must per-
form. As a result, a measure such as time may confound the
animal's willingness to perform and the time actually needed
to perform the act. Nonetheless, we can feel quite certain that
information about this work requirement is dissonant with en-
gaging in the action.

In the case of partial reward, the determination of whether
or not a dissonant relationship exists is somewhat more difficult,

DISSONANCE REDUCTION EFFECTS 41

at least at the conceptual level. Training procedures involving
partial reward always consist of a mixture of rewarded and un-
rewarded trials. As we have indicated previously, finding food
on rewarded trials is certainly consonant with performing the
given action, and therefore any dissonant relationships must
stem primarily from the unrewarded trials. But it is by no means
clear that simply the absence of some specified reward can be
considered to be a general deterrent to action. In a sense, the
absence of a given type of reward is not something that influ-
ences behavior. The absence of reward would have a deterrent
effect only if the animal were strongly motivated for a par-
ticular reward and were actively seeking it; in other words,
fasLBon-reward to introduce dissonance the animal must expect
reward.

There is a clear relationship between what we are saying
here and the concepts of expectation and disconfirmation of ex-
pectation. For our purposes, nothing more is implied than that
the present actions of the animal, such as going to and looking
into the food cup, permit us to infer that they are largely deter-
mined by its past experiences with food in this situation. Grant-
ing this, we can say that not finding a reward,, is dissonant with
performing the act only when a motivated ^aniraaLexpects^ier
ward.

"""" In summary, our operational definitions permit us to say that
pailialrey?^

eredTas consequences of an act, are in a dissonant relationship
with the performance of the act. Consequently, an animal that
experiences any of these during training should accumulate con-
siderable dissonance motivation as long as it can be induced to
continue in such activity.

The Magnitude of Dissonance

Thus far we have discussed how to determine whether or
not a relationship of dissonance or consonance exists between
two items of information. Since the existence of a dissonant re-
lationship gives rise to a motivational state, it is essential that
we specify, both conceptually and operationally, the variables
that affect the magnitude of this dissonance motivation. * Two
questions are pertinent here: (1) considering only a single dis-

42 DISSONANCE REDUCTION EFFECTS

sonant relationship between two items of information, what de-
termines the magnitude of the dissonance engendered, and (2)
considering that any given item of information may have a vari-
ety of different relationships with a number of other items of
information, what determines the total magnitude of the disso-
nance associated with this single item? We shall consider each
of these questions in turn.

In general, ^the magnitude of the dissonance that exists be-
tween any two Hems of information in a dissonant relationship
is a direct function of the importance to the individual of .each
of the items.' In the present restricted context, we deal primarily
with only two types of information, information about an action
that has been undertaken and information about the conse-
quences resulting from the action. For the sake of simplicity of
presentation, we shall develop the theory as if the importance
of the item of information about the action were a constant, re-
gardless of the context in which that action occurs. For this
simplified case, the magnitude of dissonance that exists between
items of information about an action and the consequence of
that action, when these two are in a dissonant relationship, is
a direct function of the importance to the animal of the item
concerning the consequence.

This principle, of course, says very little until one specifies
what is meant by the importance of an item of information.
Undoubtedly, any number of factors control this variable of
importance, but two of them are of primary concern in the pres-
ent context. The first involves the actual content of the item of
information: information that the consequences of an action in-
volve considerable pain or effort expenditure has more impor-
tance than the information that only a little pain or effort is
involved. The second of these factors involves the motivational
state of the animal, or at least that part of its motivational state
which is relevant to the content of the given item of informa-
tion. I^seem^reasonable-to assume.,that^if an animal is hungry,
information concerning the presence or absence of expected
food is of more importance than if the animal is not hungry;
or if an animal is very fatigued, information concerning how
much effort it must expend is of more importance than if it is

DISSONANCE REDUCTION EFFECTS 43

not fatigued. In the situations we deal with, the importance of
an item can be roughly specified either by the content of the
item or by the motivational state of the animal the hungrier an
animal js^the greater- is the magnitude of dissonances-created
whe&jt runs an alley expecting food and fails to find it Simi-
larly, the longer an animal is delayed in an apparatus before
reaching a goal box, the more dissonance is created.

A similar statement may be made concerning the role of im-
portance in consonant relationships. For example, running and
obtaining food form a consonant relationship. The item of in-
formation about the consequence of the action has a certain de-
gree of importance depending upon the content of that item
and the motivational state of the animal, A large amount of food
is of greater importance than a small amount, and any given
amount of food is of greater importance for a very hungry ani-
mal than for one only slightly hungry. Thus, consonant relations
also vary in magnitude. This magnitude is a measure of the ani-
mal's justification for performing an act and shows up as its
willingness to do so.

What we have said so far applies when only two items of
information are considered. We must now consider the case in
which a given item of information is related to several other
items. As an illustration, consider the hungry rat that runs on
a given trial in a delay-of-reward situation. The single item of
information of immediate concern is that the action has been
performed. But several consequences stem from this. First, the
animal does obtain a reward. This information is in a consonant
relationship with the action performed. At the same time, it ex-
periences an unpleasant delay. This last item of information is
in a dissonant relationship with the action. What we seek is
some form of a "combination rule" that will permit us to specify
the magnitude of the resulting dissonance.

The combination rule we propose is as follows. We sum, not
necessarily arithmetically, all the dissonant relations that may
exist, each weighted in terms of its importance, and we sum the
consonant relationships, each weighted in terms of its impor-
tance. The magnitude of the resulting dissonance is then a joint
function of these two. We are unwilling to state the exact math-

44 DISSONANCE REDUCTION EFFECTS

ematical function involved, because at the present stage of de-
velopment this would be pure guesswork. Nonetheless, this
function has two properties: (1) When the weighted sum of
the dissonant relationships is held constant, the total magnitude
of the resulting dissonance decreases as the weighted sum of the
consonant relationships increases; and (2) when the difference
of the weighted sums of the dissonant and consonant relation-
ships is constant, the total magnitude of the resulting dissonance
increases as the weighted sum of the dissonant relationships in-
creases. In other words, the magnitude of the dissonance is a
function both of the absolute value of the sum of the weighted
dissonant relationships, and of the difference between this and
the weighted sum of the consonant relationships.

In any actual empirical situation many items of information
may exist that are dissonant with, or consonant with, engaging
in an action. Thus, for example, a situation might exist where
an animal expends effort, suffers delay, and also, on occasion,
does not find food when it expects to. Given our current possi-
bilities for technical measurement, we could not specify which
of these dissonant relationships would be greatest or how much
each would contribute to the total magnitude of dissonance
when "added" together. All we can say is that each of them
would contribute.

The Reduction of Dissonance

The core of our formulation is that dissonance is a motiva-
tional state. When it exists the animal acts in ways that are
oriented toward reducing the magnitude of this dissonance. In
the present context, we are concerned only with dissonance be-
tween information about an action and about its consequences.
In general, there are only two major ways in which this par-
ticular dissonance cart be reduced. The animal can change its
information about its action, pr, alternatively, it caiL change its
information about the consequences of the action. We shall
discuss each of these in turn,

Consider an animal in a delay-of -reward experiment. It has
information that it has run in this situation. This is consonant
with the information that it obtains a reward for doing so, but

DISSONANCE REDUCTION EFFECTS 45

it is dissonant with the information that it must suffer a delay.
Consequently, some magnitude of dissonance exists, and this
creates tendencies to reduce it. One means of reducing it is for
the animal to change its behavior. Assume that there is an al-
ternative route to the goal that does not involve a delay. Choos-
ing this new alternative is consonant with its information that
the original path involved a delay. At the same time this new
action remains consonant with obtaining the reward. Thus, by
changing its behavior, it has reduced all the dissonance. Its new
action, which also implies that it refuses to engage in the original
one, is now in a consonant relationship with all the information
it has about the consequences in the situation.

This tendency to change behavior is usually the most con-
venient and the most effective way to reduce dissonance. By
changing its behavior, the organism can completely reduce dis-
sonance if the new action is ( 1 ) consonant with those items of
information that were also consonant with the previous action,
and (2) converts those items of information that were dissonant
with respect to the old action into ones consonant with the new
one. Even if a new action does not completely reduce disso-
nance, change of behavior will occur as long as the dissonance
aroused by the new action is less than that stemming from the
original one. The greater the variety of possible actions avail-
able to an animal in any situation, the greater is the likelihood
that it will adopt this method of dissonance reduction.

There are situations, however, in which a change of behavior
is not an effective means of reducing dissonance. Again con-
sider the animal in a delay-of -reward situation, but with only
one available route to the goal. We shall assume that the
weighted sum of the consonant relationships, resulting from the
fact that it obtains food, is greater than the weighted sum of
the dissonant relationships, resulting from its experiences with
the delay. Even under these conditions, considerable dissonance
can exist. If the animal now attempts to reduce the dissonance
by changing its behavior, the only possibility is to refuse to run.
In so refusing, of course, it converts its information about the
delay into a consonant relationship with the new behavior. At
the same time, however, its information that a reward is avail-

46 DISSONANCE REDUCTION EFFECTS

able is converted into a dissonant relationship with this refusal
to run. If the reward consequence has greater importance for
the animal than the delay, this means that the new action re-
sults in more dissonance than did the original one. Clearly,
under such circumstances, dissonance can not be reduced by a
change in behavior. Therefore, an animal may continue to en-
gage in a given action even though it actually experiences con-
siderable dissonance, because a refusal to act would result in
an even greater amount of dissonance.

The reader will realize that the situations with which we
are primarily concerned in this book are precisely of this type,
namely, situations in which dissonance cannot be effectively
reduced by changing behavior. Experiments on partial reward,
delay of reward, and effort are always carefully designed so as
to ensure that the animal continues to perform the required
action. In terms of our formulation, this means that the pro-
cedure has been so rigged that refusing to respond is not an
effective way of reducing dissonance.

Consequently, we are particularly concerned with how an
organism reduces dissonance when it does not change its be-
havior. The only remaining way available to it is to change the
items of information concerning the consequences of its act.
But how does it do this? Conceptually, of course, the possibili-
ties here are clear and delimitable. They are three in number:
(1) The animal can reduce the importance of those items of
information that are dissonant with the action and increase the
importance of those that are consonant with it; (2) it can rein-
terpret items of information that are dissonant with the action,
making them either irrelevant or consonant; and ( 3 ) it can make
either previously irrelevant or new items of information con-
sonant with its action. Any of these procedures will reduce the
magnitude of the dissonance.

The human being has a great capacity for self-delusion and
can employ all of these methods. With the help of social support
from others, with his freedom .to,. change jthe.iealities of Tils en-
vironment, and with Iris ability to rationalize, the hunian is*an
excellent dissonance reducer. We are dealing here, howeVer,
primarily with the white rat, presumably a much more reality-

DISSONANCE SEDUCTION EFFECTS 47

bound organism. We simply do not know which, if any, of these
various possibilities are available to the rat in reducing disso-
nance. One thing is perfectly clear, however: a theory involving
the concept of dissonance reduction must specify in fairly con-
crete fashion the mechanism, or mechanisms, by means of which
such reduction is achieved. Depending upon which mechanism
is specified, there may be different implications for behavior
even though the process by means of which dissonance is
aroused has been correctly described by us so far.

Partly on our intuitions as to what we believe is possible for
the rat, and partly because of the exciting implications for be-
havior theory, we have chosen to develop a mechanism that
provides a basis for making new items of information consonant
with behavior. But before discussing this mechanism further,
we should like to emphasize that alternative mechanisms are
possible.

An animal such as the white rat is not a simple organism.
Even when one motivation such as hunger is dominant, it simul-
taneously has a variety of other drives and motivations. We
have no intention of trying to specify these; perhaps normally
they are weak and unimportant both to the animal and to the
learning theorist. We wish to assume, however, that these sub-
ordinate motivations do exist an assumption that seems quite
plausible in terms of what is known, for example, about explora-
tory, manipulatory, and sensory stimulation needs in animals.
Granted this, such subordinate motivations may provide a
means by which the animal can reduce dissonance. If it begins
to note and pay attention to aspects of the situation that satisfy
these other motivations, it is discovering new items of informa-
tion about the consequences of its action that are consonant with
it. Loosely speaking, we can say that the animal has discovered
"extra attractions" in the situation. These can be aspects of the
action itself, of the apparatus, or of the consequences of its
behavior. We cannot specify them any more exactly without
knowing which motivations the animal has and what will satisfy
them, but we can assert that new attractions of this sort prob-
ably are discovered by the animal whenever dissonance occurs
and the behavior does not change.

48 DISSONANCE REDUCTION EFFECTS

The assumptions made in the above statement should be
emphasized. We are asserting that even though an animal has
a variety of subordinate motivations, these do not always enter
into the determination of its behavior. This is true when most
of the items of information concerning the consequences of its
act are consonant with it. If the animal is dominated by a strong
drive such as hunger, the mere fact of temporal contiguity be-
tween the subordinate motivations and their potential satisfiers
is not sufficient to relate them. The animal seeks satisfaction of
these subordinate motivations, however, if a state of dissonance
exists. In this sense, dissonance as a motivational state has a
unique property: it acts as a catalyst in relating subordinate
motives to satisfiers in a situation where this serves to reduce
the dissonance. The implication of this is that an animal that
is continuously and immediately rewarded after performing an
effortless act will not discover these "extra attractions." An
animal that experiences either partial reward, delay of reward,
or considerable effort expenditure will discover them.

We can summarize this discussion by saying that, when dis-
sonance is created Jor aa aaimal under conditions in which its
behavior does not change, "extra attractions" will develop for it
in connection with the activity, the apparatus, or the conse-
quence of the act. This occurs primarily because the pressures
to reduce dissonance result in the animal's discovering new as-
pects of the situation that serve as satisfiers for the variety of
other motivations it has at the time.

The Cumulative Aspects of Dissonance Reduction

Thus far we have discussed the theory of dissonance without
regard to any cumulative aspects. While we have defined the
conditions that create dissonance and have suggested various
means for reducing it, we have largely acted as though all of
this occurs on a single occasion. Our primary concern here,
however, is with situations of partial reward, delay of reward,
and effort, all of which typically involve a large number of re-
petitive experiences. It is therefore necessary to specify how
the state of the animal is affected by repeated experiences with
dissonant relationships.

DISSONANCE BEDUCHON EFFECTS 49

Let us consider a hungry animal that has discovered through
experience that it is rewarded with food whenever it engages
in a given action. This information about the food reward is
consonant with the information that it engages in the action.
In the following discussion we shall assume that the weighted
sum of the consonant relationships is sufficiently great so that
the animal never refuses to act.

What happens to the animal when it first acquires informa-
tion that there are aspects of the situation that are dissonant
with its action? Suppose it finds that it must expend much ef-
fort, or that it experiences an enforced delay, or that it fails to
obtain food on some occasions. All of these items of information
result in some magnitude of dissonance, which the animal at-
tempts to reduce primarily by finding "extra attractions" in the
situation. What is the state of the animal after its first expe-
rience with this dissonance?

First, consider one extreme of a possible continuum. Con-
ceivably we might have an animal that is extremely adept and
effective at reducing dissonance. On the very first occasion it
finds so many "extra attractions'* that little or no dissonance
remains. The human is sometimes capable of this. For ex-
ample, a human might persuade himself that much exercise be-
fore dinner makes the food taste better; that waiting for dinner
provides him with the one enjoyable, quiet period of each day;
and that occasionally not having dinner at all gives him a better
appreciation of the spiritual aspects of life. But even the human
cannot usually be so effective at dissonance reduction, and the
white rat certainly cannot. However, if an animal were this
effective, there would be no cumulative problem to discuss. The
next time it experienced the same situation there would be little
or no dissonance introduced and therefore, obviously, little to
reduce.

At the other end of the continuum there well may be organ-
isms, perhaps quite low in the phylogenetic order, that cannot
reduce dissonance in any of the ways we have suggested. For
these, also, there is no cumulative problem. They do not find
extra attractions in the situation, and thus there is no decrease
in the magnitude of the dissonance. Additional experiences do

50 DISSONANCE SEDUCTION EFFECTS

not modify this state of affairs in any way. For such organisms,
if our theory is correct, partial reward, delay of reward, and
effort expenditure should not enhance resistance to extinction;
if anything, they should weaken it. Very little work has been
done on the effects of dissonance-producing variables on resist-
ance to extinction in animals that are very low in the phylo-
genetic order, although there is a suggestion that fish do not
show the partial reward effect ( Wodinsky and Bittennan, 1959,
1960; Longo and Bittennan, 1960). After initial training, a 100
per cent rewarded group of fish proves more resistant to extinc-
tion than a partially rewarded group.

The white rat probably does not fall at either extreme of this
continuum. The first time dissonance occurs, it probably is able
to reduce only a minute part of the dissonance by finding "extra
attractions/' Consequently, the next time it encounters the same
situation, considerable dissonance is again aroused. Perhaps this
time it finds some additional aspects that help reduce disso-
nance. This continues to occur on successive trials. Thus, for
such an animal, we do have to account for a cumulative aspect
in dissonance reduction.

It is, of course, quite impossible to state the precise quanti-
tative function that describes the way in which "extra attrac-
tions" accumulate with the repeated introduction of dissonance,
but we can make a number of plausible specifications for this
function. First of all, it is likely that for an animal such as the
white rat these attractions build up slowly and continuously
as the number of dissonance-producing experiences increases.
Furthermore, it seems reasonable to assume that there may be
an initial acceleration in the rate of this accumulation. This is
based on the hunch that once some "extra attractions" have been
discovered, the process becomes easier. It also seems plausible
that in any given situation there is a maximum value for the
accumulation of these "extra attractions." In the usual experi-
mental situation we are discussing, this maximum is probably a
relatively low value.

One factor influencing this maximum is the nature of the
situation in which training takes place. If the development of
these "extra attractions" depends, as we assume it does, on find-

DISSONANCE REDUCTION EFFECTS 51

ing aspects of the activity or situation that act as satisfiers for
subordinate motivations, then obviously a limit is placed on
this process by what is or is not available to the animal in a given
situation. If the environment is rich, in the sense that there are
many aspects of it that can satisfy various drives, then the
amount of "extra attraction" which could develop is potentially
large. This would be most likely if an experimental apparatus
were very similar to the natural habitat of the animal involved.
If, on the other hand, the experimental situation were rather
barren of those aspects that can satisfy subordinate motivations.,
as is probably true for most of the apparatuses we use, then there
would undoubtedly be a relatively low limit placed on the accu-
mulation of these "extra attractions." In this latter case disso-
nance reduction should have only weak effects on the observed
behavior.

A second factor that might be expected to determine the
maximum development of "extra attractions" is the strength of
the animal's dominant drive. If the animal is extremely hungry,
for example, it seems plausible to assume that the subordinate
motivations are difficult to activate and that the animal is less
capable, psychologically, of discovering things that will satisfy
them; on the other hand, the activation and discovery processes
might both occur more readily when the animal is only slightly
hungry. Thus, we may reasonably assert that the stronger the
^ lower JsJtlxe .maximum

level for the development of "extra attractions."

In summary, our formulation implies
periences with a dissonance-arousing situation, the statejrf jthe
animal is different. In order to reduce the dissonance it ha
discovered "extra attractions" in the situation- that jserve to sat-
isfy its subordinate motivations. The accumulative magnitude
of these "extra attractions" depends upon the number (rf^disso-
nance-introducing experiences the animal has had, the richness
of its environment, and the strength of the dominant drive. All
else being constant, the amount of dissonance intro3uced/bn
successive occasions decreases as this accumulation process con-
tinues. ~~

TEe^discovery of these "extra attractions" clearly adds new

52 DISSONANCE BEDUCTION EFFECTS

consonant relationships. How much they increase the sum of
the weighted consonant relationships depends, of course, upon
their importance, and their importance is, in turn, a function of
the strength of the subordinate motivations. Although we know
little about these motivations, it is plausible that they are
relatively numerous and fairly stable. If this is true, then these
new consonant relationships should also be relatively stable as
long as the newly discovered attractions continue to be available
in the situation. The resulting picture of these new consonant
relationships is that of an almost intrinsic set of justifications for
continuing in the action. Even though their over-all effect on
behavior may be weak in any given experiment, they should be
relatively enduring.

There are, however, conditions that will decrease the
strength of these new attractions, either momentarily or last-
ingly. The first of these is any change in the situation. It is
certainly obvious that any change in the characteristics of the
situation may involve the elimination or modification of those
aspects that are acting as satisfiers for the subordinate motiva-
tions, and thus the elimination of the new consonant relation-
ships as well.

These "extra attractions" can also be weakened or eliminated
by changes in the animal's behavior. This is a slightly more
complicated process and needs some discussion, It will be re-
called that these attractions develop when dissonance is intro-
duced under circumstances where the animal cannot change
its behavior. They are a means of reducing this dissonance by
providing justification for continuing in that action. What
should occur, once these attractions have been developed, if the
animal is now induced to change its behavior? Such a change
in behavior can be brought about in two ways : ( 1 ) The experi-
menter can remove the original rewards in the situation, for
example, the food, as in extinction trials. This does not affect
the "extra attractions" the animal has developed, but it does
reduce the weighted sum of the consonant relationships suffi-
ciently so that the animal may now further reduce its dissonance
by changing its behavior. (2) The experimenter can provide a
very attractive alternative to the original action and the original

DISSONANCE REDUCTION EFFECTS 53

goal, thus allowing the animal to reduce the dissonance by
choosing this new alternative instead of continuing its original
behavior.

In either case, the information the animal has, that its origi-
nal action would lead to the "extra attractions/' will now be in
a dissonant relationship with its new behavior. One way in
which this new dissonance can be reduced is for the animal to
weaken the newly developed "extra attractions. " Thus, any
factor in the situation which induces the animal not to engage
in the action in which it has been trained can be expected to
start a process that is the reverse of the development of "extra
attractions."

In summary, we can expect the "extra attractions" that de-
velop in a situation, as the result of dissonance reduction, to be
stable and long enduring under normal circumstances. They
can be weakened or eliminated, however, if either the situation
is changed or the animal is induced not to engage in the original
behavior.

Implications for Behavior During Acquisition

The previous sections have defined the conditions under
which dissonance occurs and the means by which it can be re-
duced. We shall now relate these processes to the observable
performance of the animal during training or acquisition trials.

We have already stated that, in the absence of any disso-
nance, the animal's willingness to perform ( as shown by laten-
cies, running times, and similar measures) is a direct function
of the weighted sum of all the consonant relationships in the
situation. This implies that the hungrier it is or the larger the
reward the faster the animal will run. Of course, the greater the
dissonance introduced the greater is the decrease in this willing-
ness to perform. The very nature of our operational test situa-
tions for determining whether or not given variables introduced
dissonance implies this effect on willingness to perform. We
must now relate these functions to the progressive changes in
willingness to perform that occur as dissonance is created and
as it is reduced through the accumulation of "extra attractions"
in the situation.

54 DISSONANCE REDUCTION EFFECTS

To be as specific as possible, imagine an animal that is
trained to run an alley for continuous and immediate reward
with relatively little effort demanded. Assuming that the animal
is well tamed and adapted before this training begins, it should
soon reach a stable level of running. Once this has occurred,
imagine that we enforce a delay on each succeeding trial, or
else require a greater expenditure of effort. Either of these
should introduce dissonance for the first time, and this should
result in some unwillingness to run as shown by a decrease in
running speed. The animal's performance should change fairly
rapidly, but, with the same conditions on every trial, it should
then tend to become stabilized at a new value.

The situation is more complicated whenever there is varia-
bility in the conditions of training from trial to trial for example,
in partial reward situations. On some trials, the action results
in a reward, on others in a non-reward. And these consequences
occur in an unpredictable order. The same variability may be
present in experiments on delayed reward or effort expenditure
when these conditions are introduced on only a proportion of
the trials. The result is that the animal can never have complete
and certain information at the beginning of a trial of the conse-
quences that will stem from acting on that occasion. With this
uncertainty in the information, there is a question as to the
amount of variability to expect in the animal's performance on
successive trials. Largely on intuitive grounds, we should ex-
pect, in a partial reward situation, that each rewarded trial
would increase the willingness of the animal to run on the suc-
ceeding one. All the consequences of the action on that occa-
sion were consonant with that action. Similarly, we should ex-
pect each unrewarded trial to decrease this willingness because
of the dissonant consequences encountered. The result should
be more fluctuations in performance than under conditions
where each trial has the same consequences. But in any event,
it is clear that, as long as some dissonance is present, animals
being trained under either partial reward, delay of reward, or
high effort should run more slowly, on the average, than those
that receive continuous and immediate reward after little ex-
penditure of effort.

DISSONANCE REDUCTION EFFECTS 55

The above statement that under stable training conditions
even animals with dissonance will reach a stable perform-
ance level needs some qualification. Each trial provides them
with an opportunity to discover "extra attractions" in the
situation. As these accumulate, the weighted sum of the con-
sonant relationships increases, with a corresponding decrease
in total magnitude of dissonance. Consequently, their perform-
ance should gradually improve. The differences in performance
between these animals and those run without dissonance would
diminish or even disappear with continued training if the con-
ditions of acquisition permit a large accumulation of "extra at-
tractions." In fact, it is theoretically possible, under the present
formulation, that the order of performance in these two groups
could be reversed in circumstances where "extra attractions"
can be developed very readily. This, however, would undoubt-
edly be a rare finding.

Implications for Resistance to Extinction

We now come to the point of considering the implica-
tions of this formulation for measures of resistance to extinction.
Imagine two groups of animals, an experimental group trained
to engage in an action under conditions where dissonance was
created and a control group trained comparably except that
dissonance was never introduced. At the end of acquisition,
these two groups differ in at least one important aspect: the ex-
perimental group has gradually developed "extra attractions"
that are consonant with the action involved, while the control
group has not. Extinction trials are now begun. This means
that the experimenter removes from the situation all the rewards
that initially induced the animals to perform the act. In essence,
he removes all the consequences that are consonant with run-
ning which are held in common by the two groups. He does not,
however, remove any of those features that are the source of
"extra attractions" for the experimental group.

Let us now consider what happens to the control group that
never experienced dissonance. As extinction trials continue,
these animals learn that food is no longer available, and as their
certainty of this increases, they should become less and less will-

56 DISSONANCE REDUCTION EFFECTS

ing to run even though their motivation remains high. Of
course, their first discovery that rewards are no longer present
not only begins a process of change in their knowledge about
the consonant relationships in the situation, but it also gives
them their first inkling that it contains dissonant relationships.
When this dissonance exists, the animal will attempt to reduce
it. Whether the dissonance occurs on trials that the experi-
menter calls "acquisition" or "extinction" is irrelevant; the dis-
sonance can still be reduced in either of two ways. ( 1 ) The
animal can convert the consequence of the act into something
that justifies the action. This is the procedure of finding "extra
attractions" in the situation. (2) The animal can change its
behavior so that it becomes consonant with the consequence
that was experienced meaning, in the present case, that it
would refuse to ran. Here, however, there is a crucial differ-
ence between "acquisition" and "extinction" trials.

As we have pointed out previously, the animal cannot em-
ploy behavior change as a mode of dissonance reduction as
long as its expectations of finding food are strong and it is highly
motivated for such reward. To refuse to run under these circum-
stances would produce more dissonance than to continue to
run. These are the circumstances characteristic of "acquisition"
trials. "Extinction" trials, however, are different in principle in
that the animal will be able to reduce dissonance effectively by
not running. It is true that, during the first trials of extinction,
while its certainty of finding a reward is still relatively great, it
should continue in the learned behavior, and the resulting dis-
sonance would tend to reduce itself, in so far as this is possible,
by the discovery of "extra attractions." Such a process is, how-
ever, relatively slow and gradual. Meanwhile, the animal's re-
peated experiences with this extinction situation have altered
its certainties about what to expect as a consequence of running.
In essence, there has been a decrease in the weighted sum of
the consonant relationships and a corresponding increase in
the weighted sum of dissonant ones. At some point in this
process, it is clear that by refusing to run the animal will expe-
rience less dissonance as a consequence of its new behavior than

DISSONANCE EEDUCTION EFFECTS 57

if it persisted in the old running response. It is at this point that
the procedure of behavioral change becomes the dominant mode
of reducing dissonance.

This account of extinction in a control animal is relatively
imprecise and must remain so until we are willing to express the
relationships involved in a much more quantitative way. But
even at this descriptive level it is clear that extinction should be
relatively rapid for an animal that has never experienced disso-
nance during acquisition. The process hinges largely on two
factors: first, there is a change in the animal's knowledge or
certainty about the consonant and dissonant relationships that
are experienced in the situation; and second, there is an arousal
of dissonance under circumstances where it can be effectively
reduced by a change in behavior.

With this picture of the control animal in mind, we now turn
to the performance of the experimental animal during extinction
trials. As a result of its training, this animal starts the extinction
trials with an extensive background of dissonance experiences.
This training has been of such a nature that the only mode of
dissonance reduction available has been the discovery of "extra
attractions'*; behavior change was not possible. These "extra
attractions" are not removed during extinction trials. Thus,
while the control animal receives no reward at all when extinc-
tion trials start, the experimental animal continues to enjoy its
"extra attractions.'*

The initial trials of extinction should also produce gradual
changes in its certainties about the consequences that follow
the act of running just as in the case of the control animal There
should be a decrease in the weighted sum of consonant relation-
ships and a corresponding increase in the weighted sum of dis-
sonant ones as these relate to knowledge about the extrinsic
reward. Thus, one would expect a decrease in willingness to
run, but this decrease should not be of the same magnitude
as for the control animals in that the experimental animals
still have consonant relations stemming from the "extra attrac-
tions."

The experimental animals do, however, experience disso-

58 DISSONANCE REDUCTION EFFECTS

nance on each of the extinction trials. The magnitude of this
dissonance would not be as great as that experienced by the
control animals, but the experimental ones should still attempt
to reduce it. The central question is, at what point during ex-
tinction will the gradual changes that are taking place in the
weighted sums of the consonant and dissonant relationships
have reached the stage where the animal can reduce the disso-
nance more by changing its behavior than by persisting in the
old activity? Many factors would have to be taken into account
to give an answer to this question. The rate of continued de-
velopment of "extra attractions/' the rate at which information
about the absence of food is acquired, the initial strength of the
"extra attractions," and the motivations of the animal all are
relevant. Different assumptions would lead to different precise
answers to the question. Whatever the precise answer might be,
however, it is clear that, because of the "extra attractions," the
experimental animals will take longer than the controls to reach
a point where refusing to run becomes dominant. Indeed, a
refusal to run at any stage of extinction should tend to produce
more dissonance in the experimental animal than in the control
animal.

Theoretically, as we have indicated earlier, the point at
which the animal refuses to run might never be reached if the
"extra attractions" developed during training were of such a
magnitude that the experimental animal experienced little dis-
sonance when it performed the act. This outcome would be a
rare occurrence indeed considering the limitations placed on
the development of "extra attractions" by the characteristics of
the situation, the presence of a dominant motive, and similar
factors. But even in our usual experimental situations, the
arousal of dissonance during training should make for a meas-
urable increase in persistence during extinction.

Granting once more that our formulation is still largely non-
quantitative, nonetheless we believe we have stated it precisely
enough for the reader to understand the processes we envisage
and their interrelationships. The real test of the formulation,
however, is whether it can give a coherent account of the data
available on partial reward, delay of reward, effort expenditure,

DISSONANCE REDUCTION EFFECTS 59

and other dissonance-producing procedures. Even more impor-
tant is the question of whether its implications lead us to new
phenomena and relationships that have not been suggested by
other formulations. In succeeding chapters, we shall attempt
to show that both of these criteria are met by presenting a con-
siderable amount of new experimental data and by relating
these findings to the existing literature.

Evidence for the Development
of Attractions

At a gross level the empirical data that have been mentioned
in the previous chapters are consistent with the theory of dis-
sonance. This is not surprising since, if it were not so, it would
never have occurred to us to apply the theory of dissonance to
them. What we need now is a more extensive look at both ex-
isting data and new data that bear specifically on derivations
from this theory. It seems sensible first to examine the data
relevant to the basic derivation we have made, namely, that
in the process of reducing dissonance the jmimal develops a
'liking" for the activity, the place, or some ^consequence of the
action it undertakes; This derivation is basic in the sense that
it follows most immediately from the theory, and also in the
sense that the other implications concerning resistance to ex-
tinction follow from it. The question before us, then, is whether
the experimental data support this derivation. Do animals, after
repeated experience with partial reward, delAy of reward, or
effort expenditure, develop extra attractions* in the situation
which are independent of the extrinsic rewards?

On the surface, this would seem to be an easy question to
answer. Indeed, it is, if one is dealing with the verbal human
being. One can ask the subject various questions concerning
'liking" and "attractiveness" both before and after a series of
partial reward experiences and then observe whether or not
'liking" increases. Despite the negative feelings many psycholo-
gists have toward these "verbal" responses, this is undoubtedly

THE DEVELOPMENT OF ATTRACTIONS 61

the most direct way of measuring changes in the attractiveness
of a situation or activity. Aronson (1961), for example, has
shown by the use of such questions that humans increase their
liking for a color that has been associated with the unrewarded
trials in a partial reward sequence.

Despite how one feels about this procedure, however, it re-
mains a fact that it is inapplicable to the non-verbal animal.
For a non-verbal animal we are forced to infer the existence of
attractions from observation of actions. This problem has been
faced repeatedly in connnection with the study of secondary
rewards, that is, in attempts to demonstrate that attractions de-
velop through the association of stimuli with primary rewards.
The techniques used to demonstrate these secondary reward
effects have been mainly of the following types : ( 1 ) tests to see
if the animal would learn a new behavior rewarded only by the
opportunity to get back to the "attractive" situation, (2) prefer-
ence tests to see if the animal would choose the "attractive" situ-
ation over a neutral one, and (3) extinction tests to see if the
animal would persist longer in a learned action when the source
of "attraction" was present than when it was absent. All of
these tests have shortcomings, but since they are the only ones
available we shall use them to determine whether similar attrac-
tions result from dissonance reduction.

Learning a New Behavior

The most convincing evidence for the existence of an attrac-
tion would come from the demonstration that an animal will
learn a new action when the only reward is the availability of
these attractions. In order to demonstrate that, as a result of a
given set of experiences,, some previously jxeutral set of stimuli
haifbecome attractive, two things must be shown: (1) prior to
the given experiences the set of stimuli in question did not
support learning, and (2) after the experiences, the stimuli do
support learning. It is then a plausible inference that these ex-
periences have resulted in the development of some attractive-
ness. Specifically, in the case of secondary reward studies, the
animal usually has been trained to run an alley in order to find
food in a goal box. The alley has then been removed and the

62 THE DEVELOPMENT OF ATTRACTIONS

animal is required to perform some new action, such as bar
pressing, in order to gain access to the goal box, which is now
empty. It is usually known or assumed that the animal would
not learn to press the bar in order to gain entrance to the empty
box if the box had never been associated with food. If, then,
the animal does learn and maintain this bar-pressing behavior,
we conclude that the association of the box with reward during
the initial training has resulted in the box itself becoming at-
tractive.

The main difficulty of such a procedure is that it is- very
insensitive to small degrees of attractiveness. In order to pro-
vide a test situation, a totally different type of action is required
of the animal in the test than was required during training. But
this means that many aspects of the training apparatus have
been changed or eliminated along with their possible contribu-
tion to the attractiveness one is trying to measure. It is probably
for this reason that this procedure has provided very little evi-
dence for secondary reward (Myers, 1958). In the case of at-
tractiveness resulting from dissonance reduction, we also should
expect, in the usual laboratory apparatus, a relatively weak ef-
fect in the rat. Since part of this weak attractiveness may be
associated with the action involved as well as with aspects of
the goal box, changes in the activity would further weaken the
observable effects. We should thus expect that tests based on
new learning would be a very insensitive measure.

There is one outstanding example in the literature where,
by combining the effects of secondary reward with the effects
of dissonance reduction, good results were obtained. Zimmer-
man (1957) provides a demonstration of relatively strong and
lasting attractiveness by this new learning technique. His gen-
eral procedure is well illustrated by one of his studies (1959).
Animals were trained to run an alley to a goal box under partial
reward conditions. The percentage of rewarded trials was grad-
ually reduced as training proceeded until eventually rewards
were given but rarely. In terms of our formulation, this means
that the number of unrewarded, and thus the number of disso-
nance-producing trials is very great. To test for attractions that
have developed, a lever was inserted into the door of the start
box, and the animal had to learn to press it in order to gain access

THE DEVELOPMENT OF ATTRACTIONS 63

to the whole apparatus. There was, of course, no extrinsic re-
ward present during these test trials. Furthermore, as the test
trials proceeded, the animal had to press the lever an increasing
number of times in order to open the door. From the point of
view of a dissonance reduction formulation, this procedure has
two outstanding features: (1) the entire training situation is
maintained so that any attractiveness associated with aspects of
the running behavior, the alley, or the goal box can influence
the animal's desire to gain access to the apparatus; and (2) it
confounds possible secondary reward effects with the disso-
nance reduction features. Under these training and testing con-
ditions, Zimmerman obtains very clear evidence of strong and
enduring extra attractions in the situation in which partial re-
ward training has occurred.

The results of these studies are perfectly consistent with
what we would expect from dissonance theory, and to that ex-
tent they are interesting and encouraging. At the same time, it
must be admitted that they are not very helpful from a theoreti-
cal point of view. So many variables are confounded in this
procedure that it is impossible to determine how much of this
attractiveness stemmed from the processes we have emphasized
in our formulation. On the other hand, it seems clear that a less
confounded, simple test procedure makes it difficult to reveal
the existence of extra attractions which may be weak. It ap-
peared possible, however, to add to the evidence concerning
such attractions by augmenting them with a small extrinsic
reward in a simple new learning situation. If, for example, one
could find an extrinsic reward which in itself was insufficient
to produce or maintain new learning, it could be added to the
attractions developed through dissonance reduction. If this
combination produced clear-cut learning, we would then be
justified in concluding that the initial experiences of the animal
had resulted in the development of extra attractions. The fol-
lowing study was designed with this purpose in mind.

Experiment l.The Summation of Extra Attractions and
Extrinsic Reward

The idea behind this experiment was to train one group of
rats on a 100 per cent reward schedule and another on a partial

64 THE DEVELOPMENT OF ATTRACTIONS

schedule, and then to require each group to learn a new task
in order to reach the familiar goal box. To facilitate learning
of the new task, however, the animals would occasionally find
food in the goal box. The frequency of reward during the learn-
ing of this new task was intended to be so low that, by itself, it
would not produce learning. Thus, if the partially rewarded
animals developed stronger attractions in the goal box, as the
result of dissonance reduction and secondary reward, than did
the 100 per cent animals, as the result of secondary reward alone,
the partially rewarded animals would learn the new task more
rapidly.

Fifty-two female rats were trained to run a straight, un-
painted, 4-foot runway in order to reach a black goal box. The
animals were, of course, first tamed and adapted to a 22-hour
food deprivation schedule. After 14 preliminary training trials,
all of which were rewarded, the animals were divided into two
groups matched in terms of their running times. One of these
groups, the 100 per cent group, received a reward of a wet mash
pellet on each subsequent trial. The other one, the partial re-
ward group, was rewarded on only part of the subsequent trials.
All animals were given 6 trials a day for 22 days, or a total of
132 training trials. The partial reward group started these trials
on a 50 per cent schedule. As training continued, this per cent
of reward was reduced until, on the last 9 days of training, only
one of the 6 trials each day was rewarded. Altogether, a par-
tially rewarded animal received only 31 rewards during the 132
trials. The purpose of reducing the reward schedule to a very
low figure was to increase the development of extra attractions
in the goal box.

Upon completion of this training, all animals were given a
new task to learn: they were required to climb over four hurdles,
each 4 inches high, in a gray runway 68 inches long. The run-
way made four right-angled turns left, right, right, left. The
animals received 6 trials a day for 8 days on this new runway.
They were permitted 5 minutes on the first 2 trials, 3 minutes
on each of the next 4, and only one minute on the remainder to
complete a run. If they failed to enter the goal box within these
times, they were removed from the apparatus. All animals re-
ceived the same schedule of reward on this new task. To encour-

THE DEVELOPMENT OF ATTRACTIONS 65

age the animals in the beginning, the first 2 trials were rewarded.
Thereafter, the rewards were very sparse, only 5 in the next 46
trials.

Before the start of training on the new task, the 100 per cent
reward group and the partial reward group were each divided
into two subgroups. Eighteen of the 26 animals in each of these
groups had the same goal box for the new task that they were
familiar with from the initial task. Thus, any attractions devel-
oped in it during initial training should still be effective during
the new learning. On the new task, however, the remaining eight
animals from each of the groups found a very different goal box,
one differing in color, shape, size, and floor texture from the
one they had first experienced. These subgroups were essen-
tially controls. If they had developed any attractions for the
initial goal box, these should be absent or at least greatly dimin-
ished during the new learning.

One animal died during training. The results of a second
animal that was run to a new goal box were discarded because
it failed to show any learning on the new task. The composition
of the four groups is shown in Table 3 . 1.

TABLE 3.1

DESIGN OF EXPERIMENT ON NEW LEARNING AFTER PARTIAL REWARD
(EXPERIMENT 1)

Test Condition Condition of Original Learning

100 Per Cent Partial

Reward Reward

Original goal box with new task N = 18 N = 17

New goal box with new task N = 7 N = 8

Figure 3. 1 shows the average running times for each of the
four groups during the 48 trials on the new task. Since, with
such a low reward schedule, there is considerable fluctuation
in these times from trial to trial, the averages are presented for
blocks of 12 trials, that is, two consecutive days. On the first
2 trials there were no significant differences among the various
groups. It is clear that all groups showed some learning. The
fact that the two control groups, those running to a new goal box,
also showed learning is evidence that the extrinsic reward we
provided was undoubtedly somewhat larger than we had hoped

66

THE DEVELOPMENT OF ATTRACTIONS

20

15

o

5 10

2

Z

o:

tr

100% reward
o Partial reward

New goal box

Old goal box

1,2

3,4

5,6

7,8

PAIRS OF DAYS OF NEW LEARNING
(6 TRIALS PER DAY)

FIG. 3 . 1. LEARNING A NEW TASK AFTER PARTIAL AND 100 PER CENT
REWARD (EXPEBIMENT 1)

for. We must, therefore, examine the rate of learning shown by
the experimental groups in comparison to the control groups.

The group trained with a 100 per cent reward schedule, run-
ning the new task to the old goal box, does not differ materially
in its rate of learning from either of the two control groups. No
significant differences exist among them. This would tend to
indicate that the effect of secondary reward alone is very slight
even when augmented by some extrinsic reward. The slight
superiority of the partial reward group over the 100 per cent
reward group, when running to a new goal box, is probably due
to some generalization of the partial reward effect.

The animals that were partially rewarded during training
and encountered the original goal box on the new task show
a very different picture. Although starting at the same level as
the other groups on the first two trials, the animals in this group
improved more rapidly, and on the last two days they averaged
4.2 seconds per trial quite fast for this task. This value differs

THE DEVELOPMENT OF ATTRACTIONS 67

from the average of the other three at the . 05 level of signifi-
cance. It would appear from this evidence that some extra at-
traction did develop in the original goal box as the result of
partial reward experiences, and that it was stronger and more
enduring than any attraction resulting from being rewarded
there on each trial In other words, the attractions resulting
from dissonance reduction and secondary reward are clearly
greater than from the latter alone.

Considering the results of this study and those obtained by
Zimmerman, we can infer that stronger attractions develop in
the goal box during partial reward than during 100 per cent re-
ward training. This is, of course, to be expected in terms of a
dissonance reduction theory. Nonetheless, we must admit that,
at best, these extra attractions are rather weak as measured by
this new learning technique. Our conclusions would carry
greater weight if the same effect could be demonstrated by other
procedures. With this in mind, let us look at the results that have
been obtained using preference tests.

Choosing Between Alternatives

Offhand, a choice or preference procedure for determining
relative attractiveness appears to be very simple and straight-
forward. One offers the animal a choice between two alterna-
tives, such as two places or two activities, and then observes the
relative frequency with which it chooses each. Considering the
data on learning a new behavior, one is immediately inclined
to test, by a choice procedure, for the relative attractiveness
of a goal box that was rewarded 100 per cent of the time and a
goal box that was partially rewarded. Fortunately, such studies
are available in the literature. And, unfortunately, the results
of these studies seem, at first glance, to be at variance with our
theoretical expectations.

D'Amato, Lachman, and Kivy (1958) report a study in
which they tested the relative attractiveness of one goal box
that had been associated with continuous reward and another
that had been associated with partial reward. A single group
of animals was taught to run an alley. On some trials this led
to a goal box that always contained food; on the remainder of

68 THE DEVELOPMENT OF ATTRACTIONS

the trials, it led to a distinctively different goal box that con-
tained food on only 50 per cent of the trials, Following this
training, all animals were given 30 free choice trials on a single
unit T-maze with the two goal boxes, both empty, at opposite
arms of the maze. The results show that during the first 15 trials
the animals made significantly more choices of the 100 per cent
rewarded box than of the 50 per cent rewarded one. This prefer-
ence was quite consistent. Afterward, from the sixteenth trial
on, there was no clear preference for either of the two boxes.
In fact, the animals became reluctant to choose. This same
finding of an initial preference for a goal box that had been con-
tinuously rewarded over one that had been partially rewarded
is also reported by Mason (1957), using a more complex train-
ing procedure. How can one explain the apparent contradiction
between these data and our interpretation of the results of the
'learning a new task" experiment? There we came to the con-
clusion that partial reward, combining the effects of dissonance
reduction and secondary reward, resulted in stronger attractions
than secondary reward alone. Here we find data that tend to
indicate the opposite.

Let us, however, look more closely at the procedure of these
experiments in relation to the details of the dissonance formu-
lation. It must be remembered that in the choice experiments
mentioned above, the animal is choosing between alternatives
on which it has had different experiences concerning food.
Thus, one must clearly distinguish the early stages of the choice
trials from later stages. At first, when faced with the choice, the
animal's behavior is guided largely by its expectations concern-
ing the availability of food, Certainly it is not inconsistent with
dissonance theory (or any other theory) for the animal to prefer
a place where it expects food on every trial to one where it ex-
pects only occasional reward. The extra attractions developed
through dissonance reduction can hardly be expected to over-
come this difference. It is only in later choice trials, when the
animal no longer expects differential reward between the two
goal boxes, that the choices would be sensitive to the extra at-
tractions that may have developed.

There remains one disturbing aspect about these data. It

THE DEVELOPMENT OF ATTRACTIONS 69

will be recalled that in the D'Amato, Lachman, and Kivy ex-
periment, there was no preference for either goal box in the last
15 trials. By this time, however, food expectations should have
been much reduced and the choice behavior should have re-
flected whatever extra attractions existed. Why, then, did not
the animals prefer the partially rewarded to the continuously
rewarded box during these later choice trials? Our explanation
hinges around the conditions necessary for the development and
maintenance of extra attractions. As we have emphasized, these
accumulate only in circumstances where the animal does not
change its behavior. If, after this accumulation of attractive-
ness through dissonance reduction has started, the animal is
induced to change its behavior, these extra attractions weaken.
In the free choice situation of the present experiment the con-
ditions are so arranged that, during the initial trials, the animal
is induced to go consistently to the 100 per cent goal box and
to avoid the partially rewarded one. This should lead to at least
a partial breakdown of the attractions that had been established
in the latter during training, and by the time expectation of
food has vanished as a factor, there should be little basis for a
choice of either box.

In summary, it is clear that this type of experiment does not
give any direct support to our interpretation. But at least the
results are not contradictory with our formulation. We would
expect the initial preference for the continuously rewarded goal
box. Our explanation of why the animals do not eventually show
a preference for the partially rewarded one, though plausible,
may seem weak and post hoc, but it has implications that can
be tested. If it is correct, we should be able to set up choice
situations where the animal is not induced consistently to avoid
the partially rewarded goal box during the initial test trials.
Under these circumstances we should expect the extra attrac-
tions to show themselves clearly once the effects of food expec-
tation had worn off. Fortunately, there are such experimental
arrangements reported in the literature.

D'Amato, Lachman, and Kivy (1958), in the same article
referred to previously, report a second experiment in which two
groups of animals were trained on a runway. One group re-

70 THE DEVELOPMENT OF ATTRACTIONS

ceived reward 100 per cent of the time, the other only 50 per
cent of the time. Both groups were then tested for 30 trials in
a free choice situation. Now, however, the goal box of the run-
way was at the end of one arm of the T~maze and the start box
of the runway was at the end of the other arm. The assumption
was that the start box was a familiar but relatively neutral
place.

During the first 15 free choice trials both the 100 per cent
and the 50 per cent groups showed a decided preference for the
previously rewarded goal box over the start box. As one might
expect, if dissonance reduction was not complete by the end of
training, there was a tendency for the 100 per cent group to
choose the goal box somewhat more frequently during the ini-
tial trials than did the 50 per cent group. The important thing,
however, is that the partially rewarded animals did go to the
goal box; they were not induced to avoid it. Our expectation,
therefore, is that the extra attractions for these animals that
were established through dissonance reduction should not have
weakened and their effects should be apparent on later trials.
This is borne out in the last 15 test trials. Here we find that the
animals in the 100 per cent rewarded group showed a decline in
the frequency with which they chose the goal box, whereas the
50 per cent rewarded animals continued to choose it very con-
sistently. Thus, as long as the animal is not led to change its
behavior during the initial testing trials, there is evidence that
partial reward establishes stronger attractions than does con-
tinuous reward. Exactly the same kind of results have been re-
ported by Klein (1959) and by Saltzman (1949). Thu^Jther^e
is evicierLcairom botfuaew^ that

disscoiaiLce-producing experiences do lead to the development
of pxtra attractions that are at least as ^ strong; arid possibly
strongejj&an those "produced By secondary reward.

Persistence During Extinction

A measure of resistance to extinction would seem to be one
of the most obvious ways of testing for any extra attractions that
have developed in a situation, and if we can assume that even
a weak attraction tends to prolong extinction, such a test should
prove highly sensitive. Unlike a new learning procedure, it

THE DEVELOPMENT OF ATTRACTIONS 71

would not involve changes in activity and environment be-
tween training and testing, nor would it involve the problems
connected with choices between alternatives which we dis-
cussed earlier. In extinction, even weak attractions would have
a good chance of showing their effects by increasing persistence
in the task This is precisely the logic that has led to the use of
extinction tests in demonstrating secondary reward effects.

However, inferences from an extinction test for the present
purposes present some difficulties that are not encountered
using tests based on new learning or preference behavior. One
is quite willing to admit that, if an animal learns a new task in
order to get to an empty goal box, there are sources of attraction
in that box. Similarly one is willing to accept that, if an animal
chooses alternative A over alternative B, the former has attrac-
tions not found in the latter. If, however, we point to the data
which show that partial reward, delay of reward, and effort
greatly prolong extinction, many would be less willing to regard
them as supporting the idea that special attractions have de-
veloped. Throughout its history learning theory has appealed
to very different factors in attempting to explain increased re-
sistance to extinction. Because it is concerned with explaining
the strengthening and weakening of associations between stim-
uli and responses, learning theory has emphasized factors such
as stimulus similarities between training and extinction trials,
adaptation effects, and changes in the drive level of the animal.
With theoretical thinking channeled in these directions, the
possibility, that differences in extinction rates may actually be a
measurement of relative degrees of attractiveness in a situation
has been largely ignored. Therefore, if we wish to argue in favor
of this notion, it is necessary that we show at least two things:
( 1 ) that known attractions, even if weak, can prolong extinction
in a manner similar to that observed when a partial reward
group is contrasted with a continuously rewarded one; and (2)
that when an animal has dissonance-producing experiences in
an end-box, the box will act like a known attraction when it is
present during extinction trials. If these two things can be
shown, we may then convincingly interpret many of the differ-
ences observed in extinction rates as a measurement of relative
attractiveness.

72 THE DEVELOPMENT OF ATTRACTIONS

In order to test the first proposition, that known, weak at-
tractions will prolong extinction, we made use of the fact that
the white rat seemingly prefers dark places to bright ones. In
the following experiment this was tested using a brightness dif-
ferential chosen to produce only a weak difference in attractive-
ness.

Experiment 2. Influence of Natural Attractions on Extinction

The basic idea of this experiment was to train two groups
of animals in a comparable fashion, both with 100 per cent re-
ward, but with a slightly more attractive goal box for one group
than for the other. To obtain this differential attractiveness, we
used a brightness difference, since, as we have mentioned ear-
lier, there is considerable evidence that rats have a preference
for the darker of two otherwise identical places.

To be sure that this preference existed in our animals, and
to be sure that we were dealing with only a small difference in
attractiveness, we first set up the following test situation. Two
identical goal boxes were constructed, the rear walls consisting
of milk-glass plates. A 100-watt lamp could be placed behind
either of them and, when lighted, would diffuse the goal box
with a medium degree of brightness. One of these boxes was
placed at each end of the arm in a T-maze.

Eight hungry rats, after being tamed and adapted to the ap-
paratus, were given preference runs in this situation. They were
released in the stem of the T and then permitted to make a
choice between the two boxes. On half of the trials the right
goal box was lighted and the left was dark; on the other half the
left box was lighted and the right was dark. Both boxes con-
tained food on each trial

In this situation the animals failed to show any preference
between the two boxes. Instead they immediately settled into
position habits, always running either to the right or left side,
regardless of whether that box was lighted or not. Clearly, any
difference in attractiveness between the lighted and unlighted
boxes was too weak to reveal itself on this test.

The apparatus was then rearranged so that the entrances to
both goal boxes were side by side and faced directly toward the

THE DEVELOPMENT OF ATTRACTIONS 73

starting box. This latter box had a clear glass gate which en-
abled the animal, during a 10-second restraining period, to see
the interior of each goal box. Again, each o these boxes con-
tained food on every trial, with the left box being lighted on half
of the trials and the right one on the remainder. A second group
of eight hungry animals was given preference tests in this new
situation. After the 10-second restraining period, the glass door
of the start box was raised and the animal was permitted to make
a choice. Each animal was given 16 spaced trials.

Under these conditions, the animals did show a definite pref-
erence for the dark compartment. Eighty-three per cent of all
choices were for the dark side even though this varied from
right to left in a random manner. It should be noted that seven
of the eight animals made one or more runs to the lighted side,
but all of the animals chose the darker side in a majority of the
trials. One can conclude that there was a preference for the
darker compartment. This preference seemed rather weak, how-
ever, showing up only under special test conditions.

Having established that a relatively weak differential attrac-
tion existed, we then measured its influence on extinction be-
havior. Two new groups of animals were tamed and placed on
a 22-hour hunger cycle. One group of nine animals was trained
to run a 6-foot alley with a lighted goal box at the end of it on
each trial. They were given 36 spaced runs over a 9-day period.
Each run was rewarded with a pellet of food. A second group
of eight animals was trained in exactly the same way, but with
a dark goal box. All animals were then given 36 spaced extinc-
tion trials. If during extinction an animal had not entered the
goal box within 60 seconds from the time the start box door was
raised, it was removed from the apparatus.

The running times for the two groups during training were
indistinguishable. There was no evidence that the group run-
ning to the lighted box had any hesitancy about entering. Dur-
ing extinction, however, the two groups tended to diverge, as
shown in Figure 3.2. The animals running to the dark box
tended to run faster than those going to the lighted box. By
the third day of extinction the average running times for the
two groups differed, the difference being significant between

74

THE DEVELOPMENT OF ATTRACTIONS

-a

c

i

a:

LU

tr

40

30

20

10

o Lighter goal box
* Darker goal box

I 23456

DAYS OF EXTINCTION (6 TRIALS PER DAY)

FIG. 3.2. RESISTANCE TO EXTINCTION AS AFFECTED BY THE BRIGHT-
NESS OF THE GOAL Box (EXPERIMENT 2)

the . 05 and . 02 levels of significance. Using a post hoc extinc-
tion criterion of four 30-second trials, not necessarily consecu-
tive, the median number of trials to reach this criterion is 23
for the light group and 30 for the dark group. This difference
is significant between the . 05 and . 10 levels. Thus, although
the differences are not huge and dramatic, they are nonetheless
in the direction expected, considering that the animals have a
slight preference for the dark box. It should be recalled that the
preference for the darker of the two boxes was very weak. Thus,
we may conclude that slight attractions of this sort have an
effect on extinction data even when the attraction is unrelated
to the dominant motivation.

We have shown that^ w^^natjiral^attractions do prolong
step is tOLshpw

have a comparable effect when associations be-
tween the running response and the training-task stimuli are
not crucial, that is, when past experience with the go&^aJTis
th&o&ly relevant variable. We could do this by comparing^vo
groups which, during extinction, both run an alley associated

THE DEVELOPMENT OF ATTRACTIONS 75

with 100 per cent reward. One group, however, runs to a goal
box in which it has experienced partial reward while the other
group runs to a goal box in which it has always been rewarded.
Since we could find no experiments in the literature that
satisfied this requirement, we conducted our own. Our experi-
ment was designed to answer the question of whether or not
goal box attractions were independent of the schedules of re-
ward associated with the task used during extinction.

Experiment 3. Runway vs. Goal Box Effects

Two very distinctive runways and two very distinctive goal
boxes were used in this study. The goal boxes were interchange-
able with each of the runways so as to form four different task
and goal box combinations. Each animal was given trials on each
of these combinations in a random order. On three of the com-
binations the animal was rewarded on each run. On the remain-
ing combination the plan was never to reward the animal. This
design would mean that one goal box and one runway would be
associated with 100 per cent reward, and the other goal box and
the other runway would be associated with 50 per cent reward.

In this design all animals have exactly the same history of
training. Consequently, if some of the animals are extinguished
on the 100 per cent runway, half with the 100 per cent goal box
present and half with the 50 per cent goal box, any differences
in persistence must be attributed to the past experiences with
the specific goal boxes. Similarly, if the rest of the animals are
extinguished on the 50 per cent runway, half with each goal box,
any difference in persistence between these two must also be
attributed to the goal boxes. Thus, we have two tests of our
hypothesis that experiences of dissonance and dissonance reduc-
tion associated with a goal box can prolong extinction inde-
pendently of the animal's prior experiences on the task. Table
3 . 2 summarizes the design of the experiment.

The 24 rats used in this study were tamed, placed on a 22-
hour food-deprivation schedule for several days, and then adapt-
ed to eating food pellets in the two goal boxes. They were then
given 3 rewarded trials on each of the runway-goal box combi-
nations. Thereafter, they were given 8 trials a day, at 15-minute

76 THE DEVELOPMENT OF ATTRACTIONS

TABLE 3.2

DESIGN OF PKELIMINAKY EXPERIMENT ON RUNWAY vs.
GOAL Box EFFECTS (EXPERIMENT 3)

History of Reward on

Extinction Extinction

Runway Goal Box

Group 1 100% 50%

Group 2 100% 100%

Group 3 50% 50%

Group 4 50% 100%

Note: All animals had identical training experience with all four possible combinations
o runway and goal box.

intervals, for the next 20 days. All animals ran each of the four
combinations of runway and goal box equally often but in an
unpredictable order.

It was found partway through this training that a few of the
animals were beginning to make a discrimination. They became
hesitant to enter the 50 per cent goal box when it was paired
with the 50 per cent runway (the combination that was never
rewarded), but they would enter it readily when it was paired
with the 100 per cent runway. To counteract this tendency,
during the last 14 training trials on the 50 per cent runway~50
per cent goal box combination, 6 of the runs were rewarded in
an unpredictable manner. As a result of these 6 rewarded trials
the 50 per cent runway and the 50 per cent goal box were actu-
ally rewarded 57 . 5 per cent of the time.

At the completion of training, the animals were divided into
four groups of six each. One of these groups was extinguished
on each of the four combinations of runway and goal box.
Running times, from the raising of the start box door until
entrance into the goal box, were taken on each trial both during
training and extinction. Extinction trials were given at the rate
of 8 a day, with at least 15 minutes between trials. The criterion
of extinction was 6 trials, not necessarily consecutive, on which
an animal failed to enter the goal box within 120 seconds. On
such trials it was removed directly from the apparatus. On all
other trials it was retained in the goal box for 20 seconds before
being removed.

By the third day of extinction, the differences among the
groups were clear and definite. Table 3 . 3 presents the average

THE DEVELOPMENT OF ATTRACTIONS 77

TABLE 3.3

AVERAGE RUNNING TIMES (IN SECONDS) ON THIBD
DAY OF EXTINCTION (EXPERIMENT 3)

Runway Goal Box

100% Partial

100% 67.9 28.1

Partial 48.0 23.2

running times for each group of animals on the third day of ex-
tinction. This day was chosen rather than a later one since, on
subsequent days, many animals were discontinued because they
had reached the criterion of extinction.

It is clear from the table that partial reward has an effect on
prolonging runnmgiduf ing extraction both when the partial re-
ward is associated^ with the runway and when it is associated
with the goal box. The difference in ruiming times between the
100 per cent and the partially rewarded goal box groups is sig-
nificant at better than the .05 level. The difference between
the runway conditions, although favoring the partially rewarded
runway, is not significant. Precisely the same pattern of results
is shown by the number of trials to the criterion of extinction as
indicated in Table 3.4. Again, the partially rewarded goal box
makes for a big increase in resistance to extinction, significant
beyond the . 05 level. The partially rewarded runway makes for
a smaller difference which is not statistically significant. Obvi-
ously, even if runway stimuli are associated with 100 per cent
reward, partial reward experiences in the goal box have a
marked effect on resistance to extinction. Indeed, it would ap-
pear that dissonance-reducing experiences in a goal box have
resulted in the development of extra attractions. From the point
of view of dissonance theory, since attractions can also be ex-
pected to develop in connection with the activity, it is not sur-
prising to find that the runway experiences also have some effect.

TABLE 3.4

GEOMETRIC MEAN OF TRIALS TO EXTINCTION
(EXPERIMENT 3)

Runway GoalBoz

100% Partial

100% 38.9 55.0

Partial 47.9 75.9

78 THE DEVELOPMENT OF ATTRACTIONS

There are, of course, a number of difficulties with these data.
First of all, there were relatively few animals; second, there was
the difficulty during training that has been mentioned; and
finally, we did not counterbalance for initial preferences of spe-
cific runway or goal box. For these reasons a second and more
elaborate study was designed to avoid these difficulties.

Experiment 4. A Replication of Runway vs. Goal Box Effects

In this study, 60 rats, half of them males and half females,
were used. After taming, establishment of a 22-hour hunger
cycle, and adaptation to the goal boxes, they were divided into
five groups of 12 animals, with an equal number of males and
females in each. Four of these were experimental groups and
the fifth was a control. The same two runways and goal boxes
were used as in the previous experiment. One runway, painted
gray, had four right-angle turns in the sequence left, right, right,
left. Each of the four sections was 17 inches long. Four hurdles,
each 4 inches high, were spaced at equal distances throughout
the runway. The second runway was a straight alley, 48 inches
long, which contained four wooden doors under which the ani-
mal had to push. This runway also was painted gray. The same
starting box was used for both runways. One of the goal boxes
was 13 inches long, 9 inches wide, and 7 inches high. The floor
was of wood and the interior was painted black. The entrance
to it was at one end so that, after the animal entered, it ran
straight forward to the food dish. The second goal box was 18
inches long, 7 inches wide, and 7 inches high. The walls were
of unpainted plywood and the floor was hardware cloth. The
entrance was on one side so that, after the animal entered, it
had to turn to the right in order to reach the food cup. Both
boxes had guillotine entrance doors.

The design of the study, similar to the previous one, can be
illustrated by considering one experimental group. This group
was given 8 trials a day with at least half an hour between trials.
In a day's run, each of the four combinations of runway and
goal box occurred twice, but not in any set order. On three of
these combinations, the animal was rewarded with a wet mash
pellet on each run. On the fourth combination, it was rewarded
only 25 per cent of the time, in an unpredictable sequence. It

THE DEVELOPMENT OF ATTRACTIONS 79

is apparent from this description that one nmway and one goal
box were associated with 100 per cent reward while the others
were associated with 62.5 per cent reward. Any pre-experi-
mental preferences for a specific goal box or runway were coun-
terbalanced by having the partial reward associated with a dif-
ferent combination for each of the four experimental groups.
The fifth, or control group, was run in exactly the same way as
an experimental group except that all combinations were re-
warded 100 per cent of the time. All animals were run for 24
days, which resulted in 36 unrewarded runs for the experimental
animals. On unrewarded trials, the animal was left in the goal
box for 20 seconds.

At the completion of training, each group was divided into
four subgroups of three animals each. One of these was extin-
guished on each of the four combinations of runway and goal
box. Thus, for the experimental groups, one subgroup was ex-
tinguished on a combination involving a partially rewarded run-
way and a partially rewarded goal box, a second on a partially
rewarded runway and a 100 per cent rewarded goal box, a third
on a runway rewarded 100 per cent of the time with a partially
rewarded goal box, and the fourth on a runway and goal box
each of which had been rewarded 100 per cent of the time. Ex-
tinction trials were given at the rate of six a day, with at least 30
minutes between trials. The criterion of extinction was five
trials, not necessarily consecutive, on which the animal refused
to enter the goal box within 120 seconds. On these trials the
animal was removed from the apparatus. On trials when the
animal did enter the goal box, it was kept there 20 seconds be-
fore being removed.

The 12 animals in the control group showed no significant
differences in speed of running on each of the four combinations
of runway and goal box on the last four days of training (aver-
age of 5 . 5 seconds ) . There are no apparent differences among
the four combinations in terms of difficulty or preference. A
similar analysis for the four experimental groups also shows no
significant differences among the four training combinations or
among the four training groups. However, when the data were
grouped according to whether or not a runway-goal box combi-
nation was associated with partial reward, there were differ-

80 THE DEVELOPMENT OF ATTRACTIONS

TABLE 3.5

AVERAGE RUNNING TIMES (IN SECONDS) DUKING LAST Fotoa
DAYS OF TRAINING (EXPERIMENT 4)

Runway Goal Box

100% Partial

100% 4.7 4.6

Partial 5.3 6.3

ences significant between the .01 and .05 levels. Table 3.5
shows these data. There is some tendency for the animals to
run more slowly on a runway associated with partial reward
than on one associated with 100 per cent reward. On the other
hand, whether or not the goal box has been associated with par-
tial reward has no measurable effect on running speed during
training. This lack of difference is undoubtedly due to the fact
that the animal did not know which box was present until it
arrived there.

The results for the average running time on the third day
of extinction, and for the average number of trials to the ex-
tinction criterion, are presented in Tables 3 . 6 and 3 . 7, respec-
tively. It can be seen that the same pattern of results is ob-
tained here as in the previous study. Animals running to a
partially rewarded goal box extinguish at a considerably slower
rate than animals running to a continuously rewarded one. This
difference is significant only at the . 15 level for running times
on the third day, but it is significant at the . 01 level for trials
to extinction. Partial reward on the runway has a similar effect
on both measures, but neither of these differences is statistically
significant.

It will be recalled that in this experiment there was a con-
trol group that never experienced partial reward during train-

TABLE 3.6

AVERAGE RUNNING TIMES (IN SECONDS) ON THIRD DAY OF
EXTINCTION (EXPERIMENT 4)

Runway Goal Box

100% Partial

100% 34.8 24.3

Partial 32.9 21.8

THE DEVELOPMENT OF ATTRACTIONS 81

TABLE 3.7

GEOMETRIC MEAN OF TRIALS TO EXTINCTION"
(EXPERIMENT 4)

Runway Goal Box

100% Partial

100% 29.4 37.2

Partial 30.7 44.3

ing. The results for this control group are interesting. The
average running time for these animals on the third day of ex-
tinction was 87.8 seconds, significantly slower ( .01 level) than
any of the other groups. They also reached the criterion of ex-
tinction in an average of 19 . 4 trials, which is also significantly
less ( .01 level) than any of the other groups. A comparison of
these figures with the comparable ones for the experimental
group, which was extinguished on a combination of runway
and goal box that had always been 100 per cent rewarded, raises
some problems. For all four experimental groups, the general-
ized effect of partial rewards must be rather great: this is the
only conceivable explanation of the difference between two
groups that, during extinction, are both running in a situation
that was always associated with 100 per cent reward. Such a
degree of generalization in this particular experimental situa-
tion should occasion no surprise in the reader, in view of the
similarities between goal boxes and runways and the ever chang-
ing situations in which each animal was trained.

Such generalization effects also may have considerably re-
duced the magnitudes of the differences we observed among our
experimental groups. Any generalization from runway to run-
way and from goal box to goal box would have weakened the
obtained differences. But, for the point we set out to make, this
is unimportant. We have demonstrated that, as the result of
partial reward, there is an effect specific to the goal box which
results in increased resistance to extinction. This finding makes
it plausible to infer the existence of some extra attraction which
has developed through dissonance reduction.

Let us, then, summarize where we stand. We have shown
that, if we add a weak food incentive to a nev^earning situa-
tion, animals that have been partially rewarded in the goal box

82 THE DEVELOPMENT OF ATTRACTIONS

will learn the new task more quickly in order to reach that goal
box than will animals that have been continuously rewarded
there. In addition, existing literature reveals that preference
for a partially rewarded place over a continuously rewarded
one can be demonstrated as long as the conditions of the test
do not induce the animal to go away from the partially rewarded
place initially in its search for food.

Wejbtave alsp^shown thatif a known weak preference exists
for one goaTbox over another, .animals trained to the preferred
box extinguish more slowly than do animals trained to the less
preferred one. The existing literature shows that partial reward
tends to prolong extinction in a comparable fashion. From these
two findings, it is clear that the partial reward results could be
due to the development of extra attractions. Finally, we have
reported an experiment demonstrating that partial reward ex-
perience with a specific goal box prolongs resistance to extinc-
tion regardless of whether or not the runway has been associ-
ated with partial reward. All of these findings are directly
implied by a dissonance reduction interpretation which postu-
lates tie development of extra attractions.

Let us look at the relevance of these data to the alternative
explanations that we discussed in Chapter 1. Many of those ex-
planations, particularly those of Weinstock and Amsel, empha-
size that partial reward experiences ultimately produce associ-
ations between stimuli specific to the runway and the running
response. Amsel, for example, assumes that runway stimuli
eventually arouse anticipatory frustration responses which
finally become conditioned to running to the goal box. Such
an explanation seems to imply that if , after partial reward train-
ing, changes are made in the runway or in the activity required,
the partial reward effect might largely disappear.

If, however, one accepts the data we have presented about
the learning of a new task, preference tests in a T-maze, and
the results of our experiments on runway versus goal box effects,
doubt is cast on the validity of such alternative explanations.
Clearly, even though the task the animal must do to get to the
goal box is drastically changed, partial reward eflFects can still
be observed. Our own experiments have shown that runways

THE DEVELOPMENT OF ATTRACTIONS 83

associated with 100 per cent reward scarcely reduce the effect
on extinction of the presence of a goal box associated with par-
tial reward.

To what degree do the data we have presented in this chap-
ter force us to accept the interpretation that partial reward leads
to the development of extra attractions? The data we have dis-
cussed on new learning, choice behavior, and specificity of goal
box effects make a reasonably strong case for such extra attrac-
tions. Other theorists, however, might question whether or not
an explanation in terms of "adaptation" for unpleasantness or
frustration is not equally forceful. To the extent that this alter-
native is merely a verbal preference, it need not concern us. We
readily grant that unrewarded trials are unpleasant for an ani-
mal expecting food. Our interpretation also grants that, eventu-
ally, the animal finds such situations less unpleasant because of
the extra attractions it has discovered. In the situations with
which we deal, the rat never completely reduces dissonance,
and unrewarded trials undoubtedly continue to be unpleasant
to some degree.

What else may be meant by "adaptation" to unpleasantness
or frustration? The real issue is the specific mechanism that
is proposed theoretically to underly "adaptation" effects. Later
in the book, particularly in connection with minimal motivation
experiments reported in Chapter 6 and with experiments on
effort reported in Chapter 7, we shall support the interpretation
that dissonance reduction leading to extra attractions is, indeed,
the mechanism which operates.

All of the data we have discussed in this chapter have been
concerned with the effects of partial reward. It would be de-
sirable to have comparable data showing that delay of reward
and effort expenditure lead to the same effects. Unfortunately,
data from which attraction may be inferred do not exist in the
literature. Indeed, it would not be easy to collect such data in
an unambiguous way for situations involving choice and for the
learning of new tasks when the effort variable is involved. It is
much easier to study the effects of effort and delay of reward
using the extinction procedure. In the next several chapters, we
shall present evidence of this sort.

Cumulative Effects of Dissonance
Reduction

In the previous chapter, we presented evidence that extra attrac-
tions do result from dissonance reduction. The development of
these attractions, according to the theory, occurs in the follow-
ing way. The animal performs an action and then finds that the
consequences of this act do not justify it, that is, little or no ex-
trinsic reward is present. This results in a motivational state,
dissonance, which tends to reduce or resolve itself. As long as
the animal does not change its course of action, the major way
in which this dissonance reduction can occur is through the dis-
covery of aspects of the situation that satisfy some of its sub-
ordinate motives, thus providing at least partial justification for
the action undertaken. Nevertheless, as long as these extra
attractions provide only partial rather than complete justifica-
tion, dissonance is again aroused on the next similar occasion.
This, in turn, leads to further attempts at dissonance reduction
and thus to the gradual accumulation of extra attractions.

Phrased in this way, it is clear that two things are implied
about the effects of dissonance reduction: first, the discovery of
these extra attractions tends to occur primarily on the disso-
nance-producing trial; and second, the strength of these extra
attractions is an increasing function of the number of such dis-
sonance-producing experiences. In this chapter, we shall be
concerned with experimental evidence pertaining to these im-
plications in partial reward training.

Our^theory, then, asserts that the. strength of extra attrac-

CUMULATIVE DISSONANCE REDUCTION 85

tions Is a cumulative function of the number of dissonance-pro-
ducing experiences. However, the usual empirical statement is
that resistance to extinction varies inversely with the percentage
of rewarded trials. Animals rewarded 75 per cent of the time
extinguish more rapidly than those rewarded 50 per cent of the
time, and the latter extinguish more rapidly than those reward-
ed 25 per cent of the time. This implies that it is the ratio of
rewarded to unrewarded trials that is the important variable.
This statement of the relationship is consistent with Humphreys'
hypothesis ( 1939), but is clearly at variance with ours.

Is this, however, a correct statement of the empirical rela-
tion that exists? We must keep in mind that the statement is
based on experimental studies that, uniformally, have contrast-
ed various reward schedules in which either the total number
of trials or the number of rewarded trials have been equated for
the various groups. Such procedures make it impossible to assert
whether the percentage of rewarded trials or the number of un-
rewarded trials is the important variable since the two are con-
founded in the design. For instance, suppose we compare three
groups of animals, one with 75 per cent, a second with 50 per
cent, and a third with 25 per cent reward, each group having
received a total of 60 training trials. The first group, as a con-
sequence, has only 15 unrewarded trials, the second 30, and the
third 45. With this perfect negative correlation between per-
centage of reward and the number of unrewarded trials, we are
of course unable to decide which of the variables is the crucial
one in determining resistance to extinction.

A decision based on experimental data is important for our
theory and also for any form of discrimination theory that de-
pends for its explanation on contrast between training and ex-
tinction conditions.

Experimental Data on Cumulative Effects

Two studies in the literature are pertinent to this issue and,
at the same time, suggest the correct experimental design for
making a critical test. One of these (Lewis and Cotton, 1959)
compares 50 per cent reward groups that received either 16 or
60 training trials. They observe that the rats that received more

86 OJMULATIVE DISSONANCE REDUCTION

training trials take longer to extinguish; but since they failed to
include any 100 per cent reward groups in their experiment they
did not seem to appreciate the importance of their result. The
same result is reported in a study by M. G. Weinstock (1957).
She was primarily interested in studying the effect of the time
spent in the goal box on unrewarded trials on resistance to ex-
tinction after partial reward. This did not prove to be a signifi-
cant variable. As part of her design, however, she varied the
number of training trials for some partial reward groups while
keeping the percentage of reward constant. Consequently, from
her data we can determine whether or not resistance to extinc-
tion increases as a function of the number of unrewarded trials.

Specifically, she ran a continuously rewarded and a 50 per
cent rewarded group on a runway. Half of each group received
30 training trials and the other half received 60. Trials were
spaced 15 minutes apart. All animals were given 30 extinction
trials with the same spacing. Half of the animals were confined
in the goal box for 10 seconds during extinction; the other half
for 30 seconds. The average running speeds for the last 15 ex-
tinction trials are shown in Table 4.1.

It is apparent that the additional training trials had little
effect on resistance to extinction for the 100 per cent groups,
but a very considerable one for the partially rewarded animals.
The interaction between the number of training trials and the
schedule of reward was significant beyond the . 01 level regard-
less of time spent in the goal box. Clearly, resistance to extinc-
tion appears to increase directly with the number of unrewarded
trials.

TABLE 4.1

AVEKAGE RUNNING SPEEDS DURING EXTINCTION AFTER
DIFFERENT NUMBERS OF TRAINING TRIALS*

Time in Percentage

Goal Box of Reward Number of Training Trials

30 60

10 seconds 100% 20 17

10 seconds 50% 22 34

30 seconds 100% 12 15

30 seconds 50% 15 34

*Data from Weinstock (1957).

CXJ3VCC7LATIVE DISSONANCE REDUCTION 87

Although these results support our dissonance formulation,
which emphasizes the unrewarded trial as the important factor,
they are open to criticism from adherents of other hypotheses.
It can be argued that thirty trials are not sufficient to acquaint
an animal with the relative frequency of reward involved. Fur-
thermore, since only one percentage of partial reward was used,
it is impossible to determine whether or not the variable of per-
centage of reward has an effect over and above that which can
be attributed to the number of unrewarded trials. WeinstocFs
study does, however, suggest the proper design for contrasting
the effects of the number of unrewarded trials with the effects
of the percentage of rewards. What is required are several
groups of animals, some on different partial reward schedules
but equated for the number of unrewarded trials involved,
others on the same partial reward schedule but varying in the
number of unrewarded trials. Under these conditions, the two
variables can be separately evaluated. Such a study not being
available in the literature, we designed and carried out our own.

Experiment 5. The Cumulative Effect of Unrewarded Trials

A total of 146 white rats were used in the experiment. They
were approximately ninety days old at the start of training. Six
of these were discarded before extinction began either because
of illness or death. All animals were tamed and then placed on
a deprivation schedule during which they had free access to
food for two hours each day. This schedule was maintained
throughout the experiment so that the animals had been with-
out food for about twenty hours at the beginning of each day's

run.

The apparatus was an S-shaped runway. The first 9-inch
section was the start box and the last 17-inch section was the
goal box. The latter contained a food cup with a tube leading
into it. Food could be dropped through this tube on rewarded
trials once the animal had entered the goal box. Spaced at
approximately equal intervals throughout the runway were
three plywood swinging doors. These were set at a 60-degree
angle with respect to the floor so that the animals could push
under them. At each of the two turns of the runway there was
a 3-inch-high hurdle for the animal to climb over. The start box

88 CUMULATIVE DISSONANCE BEBUCTION

and runway were unpainted, but the goal compartment was
black. The whole apparatus was 6 inches deep and was covered
with hardware cloth.

The apparatus and procedure differed from the usual partial
reward study in minor ways. The activity required of the ani-
mal involved a far greater expenditure of effort than is common.
We made this requirement because, on theoretical grounds, the
magnitude of the dissonance produced on an unrewarded trial
should be a function of at least two things : ( 1 ) the failure of the
animal to find food when it expected and was oriented toward
food; and (2) the amount of effort the animal expended to get
to the place where it expected to find food. Thus, if the theory
is correct, a very effortful task should enhance the effect of dis-
sonance reduction. However, the use of this very effortful activ-
ity required that all animals have a long period of preliminary
training before the partial reward schedules could be intro-
duced; otherwise, many of them would have refused to perform.

Preliminary training consisted of first adapting the animal
to eating wet mash pellets in the goal box. It was then given 2
rewarded runs through the apparatus with all the doors open
and the hurdles removed. During the next 17 days, the animal
was given a total of 84 rewarded trials, during which the doors
were gradually lowered and the hurdles increased to full height.
For 4 following days, it was given 6 rewarded trials each day
with full effort expenditure required. Thus, there was a total of
112 preliminary trials, with constant apparatus conditions dur-
ing the last 24 All of these trials, as well as the subsequent train-
ing and extinction ones, were spaced at least 15 minutes apart.

Eleven different groups of animals, roughly matched on the
basis of running times during the last 4 days of preliminary
training, were used in this experiment. There were 11 to 16 ani-
mals in each group, approximately half males and half females.
Because of the large number of animals involved, and the large
number of trials required in some conditions, not all groups of
rats were started at the same time. Altogether, the data collec-
tion lasted almost one calendar year.

Partial reward schedules were introduced on the day follow-
ing the completion of preliminary training. Thereafter, animals
were given 6 training trials a day. On rewarded trials the ani-

CUMULATIVE DISSONANCE REDUCTION 89

mal was given a large wet mash pellet which took an average
of 40 seconds to eat; on unrewarded trials the animal was kept
in the goal compartment for the same length of time.

The over-all design of the experiment, that is, the exact num-
ber of unrewarded trials and the total number of trials given to
animals in each of the eleven experimental conditions, is shown
in Table 4.2. It can be seen that three different groups of ani-
mals were run with a 33 per cent reward schedule. The total
number of trials they received was varied so that one group ex-
perienced 16 unrewarded trials, a second group experienced 27
unrewarded trials, and a third group experienced 72 unrewarded
trials. Similarly, three different groups were run on a 50 per
cent reward schedule, each group experiencing either 16, 27, or
72 unrewarded trials. To save experimental time, only two
groups were run on a 67 per cent reward schedule. The group
that would have experienced 27 unrewarded trials was omitted.

It is clear from an examination of the table that the total
number of training trials varies considerably. The smallest num-
ber of trials after preliminary training is 24 for the 33 per cent
reward group that experienced 16 unrewarded trials. The larg-
est number of total trials following preliminary training is 216
for the group that experienced 72 unrewarded trials on a 67 per
cent reward schedule. In order to have a comparison for the

TABLE 4.2

TOTAL NUMBER OF TRIALS BEYOND PRELIMINARY TRAINING FOR
EACH GROUP IN PARTIAL REWARD EXPERIMENT (EXPERIMENT 5)

_ , Number of Unrewarded Trials

Reward

Schedule 16 27 72

33% 24 42 108

(14)* (11) (16)

50% 31 f 54 144

(12) (13) (13)

67% 48 216

(11) - (11)
f (11)

100% \ 54 (14)
[216 (14)

* Numbers in parentheses refer to the number of animals in each group,
f One extra unrewarded trial was given to the animals in this group to bring the num-
ber of unrewarded trials to 16 in 5 days of partial reward training.

90 CUMULATIVE DISSONANCE BEDUCTION

effect of sheer total number of trials, three different groups were
run with 100 per cent reward. One of these groups began ex-
tinction immediately after the preliminary training was finished.
No additional trials were given. A second group was given 54
trials, and a third group was given 216 additional trials before
extinction was started. Thus, the range of total number of trials
for the three groups on a 100 per cent reward schedule brackets
closely the range of total number of trials of the partially re-
warded animals.

During training, the order of rewarded and unrewarded
trials was prearranged so as to be unsystematic within each day.
However, of the 6 trials each day there were 4 unrewarded trials
in the 33 per cent group, 3 in the 50 per cent group, and 2 in the
67 per cent group. The last trial on the last day before extinc-
tion was rewarded for all animals in all conditions. Extinction
trials were run in the same manner as the acquisition trials that
is, each animal was given 6 trials a day, spaced at intervals of
at least 15 minutes. Of course, no food was obtained in the food
compartment on extinction trials. When the animal entered the
food compartment it was kept there for 40 seconds and then
returned to its home cage. If the animal did not enter the food
compartment within 180 seconds after the start box door was
raised, it was taken out of the apparatus. Six such trials, not
necessarily consecutive, were used as a criterion of extinction.

The main over-all results of this experiment are presented
in Table 4 . 3 and in Figure 4 . 1. These present the average num-

TABLE 4.3

AVERAGE NUMBER OF TRIALS TO
EXTINCTION GEOMETRIC MEANS (EXPERIMENT 5)

Reward Schedule Number of Unrewarded Trials

33%
50%

67%

100% (zero trials) 15.2

100% (54 trials) 19.8

100% (216 trials) 22.5

16

27

72

26.3

32.3

54.5

26.7

36.1

47.3

30.2

55.5

CUMULATIVE DISSONANCE KEDUCTION

91

ber of trials required by each of the eleven groups to reach the
criterion of extinction. The data are presented, and were ana-
lyzed, in terms of geometric means for two reasons. First of all,
the distributions of number of trials to reach the criterion are
highly skewed. Using logarithms tends to normalize them and
to facilitate statistical analysis. The other reason is apparent in
Figure 4.1. Presenting the data in these terms makes the rela-
tionships pleasingly linear.

The results for the groups rewarded 100 per cent of the time
show the influence on extinction of the number of training trials
involved. It is clear from Table 4 . 3 that all three of these groups
extinguish very quickly. The geometric means are 15.2, 19.8,
and 22.5 trials, respectively, for the groups having 0, 54, and
216 trials in addition to preliminary training. To realize fully
how rapid this extinction is, one must remember that these
means include the 6 criterion trials on which the animals refused

.9 50

3 40

o

1

X

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3

30

20

IQ.

o 33 % reward ( smallest # of trials)

50% re ward

67% reward (largest # of trials)

16

27

72

NUMBER OF UNREWARDED TRIALS

FIG. 4 1. RESISTANCE TO EXTINCTION AS A FUNCTION OF THE NUMBER
OF UNREWARDED TRIALS (EXPERIMENTS). N.B. For those groups receiv-
ing zero unrewarded trials (100 per cent reward) the filled circle repre-
sents the largest number of trials and the open circle, the smallest number.

92 CmiUIATTVE DISSONANCE BEDUCTION

to enter the goal compartment within 180 seconds. Increasing
the number of trials for continuously rewarded groups obviously
has some effect on resistance to extinction. This effect, however,
is slight. An analysis of variance indicates that the difference
among these three groups is significant at the . 05 level, but most
of this difference is due to the very rapid extinction of the group
that had zero additional trials after preliminary training. The
difference between the 54 and 216 trial groups is small and not
significant. Undoubtedly, the zero trial group had not adjusted
adequately to the effortful task by the end of preliminary train-
ing. This is reflected in the running times of the three groups
on the last day of training: 3.6 and 2.8 seconds for the 54
and 216 trial groups, but 6.9 seconds for the zero trial group.
Clearly, the zero trial group was still running slowly when ex-
tinction began. Nonetheless, we must allow for some slight
effect of additional rewarded trials in evaluating the remainder
of the data. As may be seen, however, this effect is negligible
when compared with the influence of unrewarded trials.

Perhaps the most outstanding result in Table 4.3 is the fact
that each of the partially rewarded groups takes more trials, on
the average, to reach the criterion of extinction than does any of
the continuously rewarded groups. This is true regardless of the
number of training trials given. In other words, the effect of
unrewarded trials is completely different from that of rewarded
trials. The impression given is of a different and unique process
adding its effect to that associated with traditional reward fac-
tors.

The manner in which this different process operates can be
seen a little more clearly by contrasting the various groups when
the number of unrewarded trials is held constant. For the same
number of unrewarded trials, variation in the per cent of reward
has little or no effect on resistance to extinction. For groups
having 16 non-rewards, the average trials to criterion range from
26 . 3 to 30 . 2. An analysis of variance indicates that these differ-
ences do not approach significance. Similar results are obtained
for those groups that had 27 and 72 unrewarded trials. The
ranges are small and the differences that exist are not signifi-
cant. These results make it obvious that the usual negative cor-

CUMUIATIVE DISSONANCE REDUCTION 93

relation between percentage of reward and resistance to extinc-
tion is artifactual. It comes about because the usual procedure
in such studies results in a complete confounding of the number
of unrewarded trials with percentage of reward. In f act, in the
present data there is a small but interesting reversal of the usual
relationship. When the number of unrewarded trials is held
constant, there is a tendency for those groups that received the
highest percentage of reward to take slightly longer to extin-
guishundoubtedly because the groups with the higher per-
centage receive more rewarded trials than do groups with a
lower percentage. The magnitude of this effect on resistance
to extinction is comparable to the differences observed among
our continuously rewarded groups.

The data in Table 4 . 3 make it equally clear that as the num-
ber of unrewarded trials is increased, regardless of the percent-
age of reward involved, resistance to extinction increases mark-
edly. Within each ratio of reward, the differences between the
16 and 72 non-reward trial groups are significant well beyond
the . 01 level. To judge the magnitude of this effect, one must
recall that it takes continuously rewarded animals about 20
trials, on the average, to reach the criterion of extinction. With
only 16 non-rewards, this increases to slightly under 30, or about
half again as much. With 72 non-rewards, the average increases
to approximately 50 trials, or two and one-half times that shown
by continuously rewarded animals. In light of these results, one
must conclude that the process by means of which partial re-
ward increases resistance to extinction is a process that occurs
on unrewarded trials. Furthermore, this effect accumulates as
the number of such trials increases. For all practical purposes,
in our data this effect is independent of any interaction between
rewarded and unrewarded trials.

The results discussed so far have been plotted in Figure 4.1.
The black circles represent 67 per cent reward, the crossed
circles 50 per cent reward, and the open ones 33 per cent re-
ward. For the 100 per cent reward groups, that is, the ones with
zero unrewarded trials, the black, crossed, and open circles rep-
resent the groups having 216, 54, and trials in addition to
preliminary training. A glance at this figure makes it apparent

94 CIJMXJLATIVE DISSONANCE KEDUCTION

that the ratio of reward during acquisition has only a negligible
effect.

It is interesting, and rather surprising, that we obtain no
effect whatever that might be attributed to the contrast between
acquisition and extinction, the notion underlying any discrimi-
nation hypothesis that rests heavily on the f amiliarity the animal
acquires with the relative frequencies of rewarded and unre-
warded trials. From such a hypothesis, it could be argued that
groups on different ratios of reward might not differ in resistance
to extinction when each has received only a few unrewarded
trials, since, with so few training trials, the various ratios of re-
ward would not have been distinguished. Thus, all groups might
act alike when tested on extinction. However, with large num-
bers of trials each group should be rather certain about the char-
acteristics of the ratio it was on. This line of argument implies
that the differences in Figure 4.1 among the various ratio of
reward groups should begin to increase as the number of unre-
warded trials increases. It is perfectly clear, however, that this
does not occur. The magnitudes of these differences are practi-
cally indistinguishable throughout the range studied. And cer-
tainly 72 unrewarded trials (which means that even the 33 per
cent reward group has been on this schedule for 108 trials ) is
long enough for an animal to be fairly certain about the ratios
involved.

TABLE 4.4

AVERAGE RUNNING TIMES (IN SECONDS) BY RATIO
OF REWARD (EXPERIMENT 5)

Reward Schedule

33% 50% 67%
ACQUISITION

Next to last day (6 trials) 7. 18 3.35 2.66

Last day (6 trials) 5.40 3.05 2.75

EXTINCTION

Trials 1-3 6.29 3.77 2.61

Trials 4-6 8.11 6.45 5.38

Trials 7-9 13.70 9.15 9.52

Trials 10-12 18.92 11.23 13.03

Trials 13-15 24.91 20.93 17.69

Trials 16-18 26.09 22.93 21.46

CUMULATIVE DISSONANCE BEDUCHON 95

It Is possible, however, that we do not see the effect of ratio
of reward because we are looking at the data in a rather gross
manner. The effects of contrast with acquisition may show
themselves only early in a series of extinction trials. To check
on this, we may look at the average running times for the vari-
ous groups during the initial stages of extinction.

Table 4.4 presents the data on the average running times
for each percentage of reward condition. All groups having the
same percentage of reward have been pooled for this purpose
without regard to the number of unrewarded trials. In this way
we can see the effect of percentage of reward when the average
number of unrewarded trials is the same (except for the 67 per
cent reward schedule where the condition of 27 unrewarded
trials is missing ) . The first two rows of Table 4 . 4 are the average
running times for the final two days of acquisition, each number
being based on 6 trials. The last six rows are the averages for
successive sets of 3 trials during the first 18 trials of extinction.
The same data are presented graphically in Figure 4 . 2. Clearly,
there is no difference in the rate of extinction during early ex-
tinction trials for the three different ratio of reward groups.
The extinction curves for all three conditions tend to be parallel.
Thus, even in the initial stages of extinction, the ratio of reward

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o

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30

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P 20

10

33 % reward
50% reward
67% reward

Next to
last six

Ust 1-3 4-6 7-9 10-12 13-6 16-18
six

TRAINING TRIALS EXTINCTION TRIALS

FIG. 4.2. AVERAGE RUNNING TIME BY RATIO OF REWARD (EXPERI-
MENT 5)

96 CUMULATIVE DISSONANCE SEDUCTION

is quite unimportant in determining the rate of extinction. These
data fail to support any notion about contrast effects. Certainly,
if such contrast played a role in detennining this behavior, we
would anticipate some difference in the rate of extinction be-
tween the 33 per cent and 67 per cent reward groups for at least
the first 9 to 12 trials. During training the 67 per cent reward
groups experienced only two unrewarded trials each day where-
as the 33 per cent reward groups experienced four such trials a
day. From any contrast hypothesis, one should anticipate that
the fourth, fifth, and sixth extinction trials would have a much
greater impact on the 67 per cent than on the 33 per cent ani-
mals. Similarly, the next three to six trials should augment this
difference. With the restricted "random" schedules of rewards
used in training these groups, these trials should clearly inform
the 67 per cent animals that conditions have changed. The per-
formance data on these trials, however, provide no evidence that
such an effect occurs.

It is also interesting to note that, when the number of unre-
warded trials are equated as in these data, there is a direct rela-
tionship between the running speeds during acquisition and
extinction. The animals trained with 33 per cent reward are
definitely slower at the end of training than are the other ani-
mals. This difference is maintained throughout the first 18 trials
of extinction. It will be recalled that a similar slight difference

TABLE 4.5

AVERAGE RUNNING TIMES (IN SECONDS) BY NUMBER OF
UNREWARDED TRIALS (EXPERIMENT 5)

Number of Non-Rewards

16 27 72
ACQUISITION

Next to last day ( 6 trials) 3 . 29 5 . 35 5.74

Last day (6 trials) 3.26 3.99 4.54

EXTINCTION

Trials 1-3 3.94 4.75 4.97

Trials 4-6 7.82 4.26 7.61

Trials 7-9 16.04 9.71 7.31

Trials 10-12 22.48 13.60 8.27

Trials 13-15 34.07 16.41 13.79

Trials 16-18 43 . 25 18 . 61 9 . 16

CUMULATIVE DISSONANCE REDUCTION

97

was found in the number of trials required to reach the criterion
of extinction.

Finally, we need to look briefly at the data on running times
during the initial trials of extinction when the groups are com-
bined according to the number of unrewarded trials. These data
are presented in Table 4.5 and Figure 4.3, It is apparent that
the number of unrewarded trials makes an all-important differ-
ence in the rate of extinction. The groups with the fewest un-
rewarded trials extinguish the most rapidly, and those with the
most unrewarded trials extinguish the least rapidly. This differ-
entiation begins on the first days of extinction and is very marked
by the ninth trial. Thus, the differences we noted in terms of
average trials to a criterion of extinction are characteristic, and
not something that only show up late in the extinction process.

In summary, the results of this study lend support to two
implications from dissonance theory. They support the idea,
first, that the processes producing^, increased resistance to ex-
tinction after partial reward occur primarily on the unrewarded
trial itself and, second, that these dissonance reduction effects

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40

30

I 20

z

z>
o:

$ 10
o:

* 16 Unrewarded trials
o 27 Unrewarded trials
x 72 Unrewarded trials

Next to
last six

Lost 1-3 4-6 7-9 10-12 13-15 16-18
six

TRAINING TRIALS EXTINCTION TRIALS

FIG. 4.3. AVERAGE RUNNING TIME BY NUMBER OF UNREWARDED
TRIALS (EXPERIMENT 5)

98 CUMULATIVE DISSONANCE BEDUCTTON

ajc0 cumulative. In addition, this study makes untenable a vari-
ety of other explanations of the partial reward effect. Any ex-
planation that relies, in whole or in part, on the contrast between
acquisition and extinction trials is no longer tenable.

Our confidence in dismissing such explanations is increased
because of an additional study reported by Theios ( 1961 ) . He
tested the effects on resistance to extinction of interpolating a
series of 100 per cent rewarded trials between the partial re-
ward training and the extinction test. Specifically, Theios tested
the resistance to extinction of three identically trained partial
reward groups. One group was extinguished immediately after
partial reward training; another had 25 additional trials with
100 per cent reward before extinction; and a third had 70 such
100 per cent rewarded trials between partial reward training
and extinction. In addition, two control groups which received
only 100 per cent reward were run.

Table 4.6 presents the results of this experiment. It is clear
that the interpolation of continuously rewarded trials between
partial reward training and extinction has little or no effect.
Animals trained with 100 per cent reward take slightly over 30
trials, on the average, to extinguish, whereas the partial reward
animals take from 50 to 66 trials. If contrast between acquisi-
tion and extinction conditions were important, one would expect
interpolated 100 per cent reward trials seriously to weaken the
partial reward effect. After all, such interpolated trials make for
a sharp contrast when extinction begins.

TABLE 4.6

PARTIAL REWABD EFFECTS ON RESISTANCE TO
EXTINCTION AFTER INTERPOLATED CONTINUOUS REWARD TRIALS*

Number o Average Number

Interpolated of Trials to

Original Training 100% Reward Trials Extinction

Partial 61

Partial 25 66

Partial 70 50

100% 33

100% 70 31

* From Theios (1961).

OT[MIJIATIVE DISSONANCE REDUCTION 99

The Relation of Dissonance to Non-Reward

Theoretically, not all instances of absence of reward should
produce dissonance. Our formulation implies that if an animal
performs an act, even though it is very effortful, and finds an
adequate reward, little or no dissonance is introduced. On the
other hand, if the animal performs the act and does not find a
reward, dissonance is aroused and dissonance reduction occurs.
The crux of this formulation is this; the experiencing of non-
reward per se is not sufficient to arouse dissonance. It is only
when an animal performs an act in the expectation of being re-
warded that not obtaining the reward generates any dissonance.
To add weight to our theoretical interpretation it would be use-
ful to show that experience with non-reward, if such experience
fails to produce dissonance, does not increase resistance to ex-
tinction.

To demonstrate this, we need a situation in which an animal
experiences occasional non-rewards in a goal box, the non-re-
wards coming only on occasions when it has not performed any
definite act oriented toward getting food and thus does not ex-
pect food. Under these circumstances, no dissonance should be
aroused since the absence of food is not dissonant with the ani-
mal's behavior. Consequently, no extra attractions should de-
velop. In an attempt to show this, we designed and ran the
following study.

Experiment 6. -Placing vs. Partial Reward Efects

The apparatus for this experiment was an 8-foot-long en-
closed runway leading to a black goal box. A delivery tube was
centered above the food dish so that, on rewarded trials, a pellet
of wet mash could be dropped after the animal had entered the
goal box. Three hurdles, each 3 inches high, were spaced evenly
throughout the alley.

Three groups of rats, approximately ninety days old at the
beginning of the experiment, were trained on this apparatus.
There were 12 animals in each group, half males and half fe-
males. A 100 per cent reward group was rewarded on each trial;
a 50 per cent reward group was rewarded on half the trials and

100 CUMULATIVE DISSONANCE REDUCTION

retained In the goal box for 20 seconds without food on the other
half. The third group, a placed group, was trained in an unusual
fashion. These animals ran the alley and found food on half
their trials just as did the 50 per cent reward group. On the other
half of the trials, however, these animals did not run the alley.
Instead they were placed directly in the goal box, immediately
in front of the entrance door, and then retained there for 20 sec-
onds without food. Thus, their experiences in the goal box were
directly comparable to those of the partially rewarded animals.
However, whenever these animals ran the alley this act of run-
ning was rewarded. They were unlike the partially rewarded
animals in that, for the placed group, non-reward was not dis-
sonance producing because very quickly these animals learned
not to expect food when placed in the goal box.

All animals were tamed and placed on a 22-hour deprivation
schedule. They were given 4 preliminary trials of eating in the
goal box, followed by 6 rewarded trials during which the hurdles
were gradually increased to their full height. Thereafter, all
animals were given 6 trials a day, spaced at least 15 minutes
apart, for a total of 72 training trials. For the 50 per cent reward
animals, 3 of these trials each day were unrewarded, occurring
in an unpredictable order. These same 3 trials were unrewarded
for the placed group.

This training was followed by 48 extinction trials for all ani-
mals, again at the rate of 6 a day, with at least 15 minutes be-
tween trials. Running times from the opening of the start box
door until entrance into the goal box were taken on each trial
both during training and extinction. If an animal had not en-
tered the goal box within 90 seconds, it was removed from the
apparatus. During the course of the experiment one animal in
the placed group died, leaving only 11. By the end of training
all three groups were running about equally fast. On unreward-
ed trials, the placed group showed evidence that it did not look
for food.

Table 4 . 7 presents the data for the three groups on the aver-
age number of trials required to reach a criterion of extinction
of two 60-second trials, not necessarily consecutive. This arbi-
trary criterion was chosen since all animals did reach it within

CUMULATIVE DISSONANCE REDUCTION 101

TABLE 4.7

THE EFFECTS OF PLACING vs. PARTIAL REWARD
ON RESISTANCE TO EXTINCTION (EXPERIMENT 6)

Number of Trials
Training Condition to Extinction

50% Reward (N = 12) 27 . 8

Placed (N = 11) 18.2

100% Reward (N = 12) 20 . 9

the 48 extinction trials. It may be seen in the table that the
usual effect of partial reward is obtained. The 50 per cent reward
group requires 27.8 trials whereas the 100 per cent reward
group requires only 20 . 9 trials to extinguish. This difference
is significant at the . 05 level. Looking at the data for the placed
group, we find that the mere experience of being in the food
compartment without food does not increase resistance to ex-
tinction. The placed group extinguishes in 18.2 trials, in con-
trast to the 27.8 trials of the 50 per cent group, again a differ-
ence significant at the . 05 level. Thus, there is no evidence that
extra attractions for a situation develop merely because non-
reward experiences are associated with it. Resistance to extinc-
tion is increased only if non-reward signifies that the perform-
ance of a given action is not justified, that is, if dissonance is
introduced.

We willingly grant that the results of this study can be in-
terpreted in a number of different ways. The important ques-
tion, however, is whether the mere experience of non-reward in
the goal box is sufficient to build up resistance to extinction, or
whether this experience has to disconfirm an expectancy. The
results tend to confirm the assumption we are making that dis-
sonance and dissonance reduction do not occur in the former
case.

Summary

The evidence in this chapter supports three basic assump-
tions underlying our dissonance explanation^? partial reward
effects on resistance to extinction. (1) we have shown that the
crucial factor is the unrewarded tridUThe percentage t of ^reward
is of little or no consequence. ( 2 ) We have shown that the effect

102 GOMTILATIVE DISSONANCE REDUCTION

of these non-rewards is cumulative. When groups are equated
on number of unrewarded trials, regardless of percentage of
reward, they show comparable magnitudes of resistance to ex-
tinction. ( 3 ) We have demonstrated that it is not the experience
of non-reward per se that is crucial. Rather, it is only when this
experience is related to the expectation of reward that it has
any influence on resistance to extinction. This implies that dis-
sonance and dissonance reduction occur only when the animal
has taken an action and then finds that this action is not justified
by its consequences.

What has been shown for partial reward procedures should
also apply to delay of reward and effort expenditure. In these
instances the delay, or the effort expended, introduces disso-
nance rather than expecting and not obtaining reward. Resist-
ance to extinction should be an increasing function of the num-
ber of such dissonance-producing trials. At present there are
no data in the literature strictly relevant to this issue, although
some inferences can be made in the case of delay of reward from
the study done by Wike and McNamara ( 1957 ) . They gave all
of their groups an equal number of training trials, but they varied
the percentage of trials on which the reward was delayed. Re-
sistance to extinction increased directly as the percentage of
these delay trials increased. In their study, of course, the num-
ber of delay trials and the percentage of delay were directly
correlated. Thus, while they interpret the results as though the
percentage were the crucial variable, it is more probable in
terms of what we have shown in this chapter that the number of
such delay experiences is the primary variable.

The Effects of a
Zero Reward Schedule

In the previous chapter, the outstanding conclusion was that
partial reward effects depend primarily on the absolute number
rather than the percentage of unrewarded trials. There is, un-
fortunately, one ambiguity in the interpretation of these find-
ings: all of the experimental tests have involved situations in
which the animal has experienced both reward and non-reward
in exactly the same place. Consequently, it is possible to frame
any number of explanations that hinge on this fact. For instance,
AmseFs frustration hypothesis ( 1958) assumes that the reward-
ed trials are necessary to enable the animal to establish an an-
ticipatory goal response. On unrewarded trials, the conjunction
of these anticipatory goal responses and the absence of reward
result in the arousal of frustration. Thus, a specific kind of
interaction between rewarded and unrewarded trials is central
in this hypothesis.

From our point of view, dissonance will be aroused, and dis-
sonance reduction will take place, as long as the animal^ c
induced to continue performing a motivated act even
reward is never obtained. T^Qrjetically^extr.i. attractions would

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develop even if an animal were trained on a zero reward sehed-
ule, that is, one on which it repeatedly performs an act but is
never rewarded for it. If such a performance could be shown,
it would be very strong evidence for the dissonance explanation
and at the same time would rule out alternative interpretations
such as the one suggested by Amsel.

104 THE EFFECTS OF ZERO REWARD

an animal to perform an act consistently if there are no incentives
at all. We can, however, approximate this situation, as we shall
see later, by inducing an animal to go consistently to a place that
is never directly associated with reward. We shall refer to such
an approximation as a "zero reward" situation.

Any experiment that would permit us to say, unequivocally,
that a zero reward schedule had resulted in extra attractions
must face, and solve, certain problems. Let us assume that we
have trained an animal to perform an act repeatedly and that
this act has never been directly rewarded. As a consequence,
dissonance has been introduced in each trial, and the resulting
dissonance reduction has led to the discovery of extra attractions
in the situation. The initial problem is how we demonstrate that
these extra attractions are present, that is, against what base
line do we compare the performance of this animal? Ideally, we
should like a control animal for whom both the activity and the
situation are familiar but neutral in attractiveness. Unfamili-
arity might well result in emotional factors that would inhibit the
animal's performance. Clearly, however, this combination of
neutral attractiveness with familiarity can never be produced
with any assurance. If experience with the activity and situ-
ation is given in conjunction with reward, there is every reason
to expect that some attractiveness, as the result of secondary
reward, will develop. If this experience is given in the absence
of reward, but under conditions that preclude the operation of
dissonance reduction, there is every reason to expect that some
negative incentive value will result. Thus, a base line of neutral
attractiveness is probably unattainable.

The inevitable conclusion is that we must contrast our zero
reward animal with one that has experienced a 100 per cent re-
ward schedule. This ensures equal familiarity for both animals
but limits us to contrasting two forms of attractiveness, that
based on dissonance reduction versus that based on secondary
reward. Granted this necessity, it is clear that only one type of
empirical outcome has an unambiguous interpretation from the
point of view of dissonance theory. If the zero reward animal
persists longer during extinction than the 100 per cent reward
animal, some attractiveness obviously has developed as a result
of dissonance reduction.

THE EFFECTS OF ZERO REWARD 105

Another condition must also be fulfilled before the results of
a zero reward schedule are interpretable from the point of view
of dissonance reduction. First of all, as we have emphasized
previously, the training situation must be so arranged that the
animal does not change its behavior. Any indication that the
animal is refusing to run counterindicates the building up of
extra attractions. Thus, something must be provided in the ex-
perimental situation which will guarantee that the animal con-
tinues to run.

The main type of evidence available on this question of zero
reward effects is illustrated by a recent study by Marx (1960).
He ran a single group of animals on a runway. Three different
end boxes were used, each on a third of the trials, but only one
of these ever contained food. The animals were thus trained on
a 33 per cent reward schedule, the reward being associated with
only one end box. Of the various subgroups on which he con-
ducted extinction tests, two are of particular interest to us. One
of these groups had the formerly rewarded end box present dur-
ing extinction while the other had one of the unrewarded ones.
The former group required 45.7 trials to reach a criterion of
extinction whereas the latter required 50 . 7 trials. Although this
difference does not reach statistical significance, it does indicate
that non-reward produced effects as strong as those attributable
to secondary reward. It must be admitted, however, that the
results are ambiguous for our purposes, for the training situation
permitted the animal to anticipate which end box was present
on any trial. In fact, the training data indicate that the animals
were able to establish a discrimination between the rewarded
and unrewarded trials. Such discrimination that is, not expect-
ing reward on unrewarded trials would retard the development
of any extra attractions.

This development of discrimination was partially controlled
in a study done by Bitterman, Feddersen, and Tyler (1953).
Their apparatus consisted of a runway ending in a gap that the
animal had to jump before it could enter the goal box. At the
entrance to the goal box there was a cardboard door which pre-
vented the animal from seeing the interior of the box while
jumping. All animals in the study were given 10 massed training
trials a day for 10 days. Half of these trials were rewarded and

106 THE EFFECTS OF ZERO REWABD

half were not rewarded. The interior of the goal box was one
color (e.g., black) on rewarded trials and a different color (e.g.,
white) on unrewarded trials. Thus, the first color should have
acquired secondary reward value because it was always asso-
ciated with primary reward; the second color, of course, should
not have acquired secondary reward value. But, if dissonance
reduction occurred, this second color should have become an
incentive in its own right because the animal consistently ex-
pended considerable effort to go there without any reward to
justify this behavior. The reason the animal continued in this
nonsensical behavior is obvious: at the time it jumped the gap
it was unaware, because of the cardboard door, that the unre-
warded box was present. But, having performed the act and
then not having been rewarded for it, it should have experienced
dissonance.

At the completion of training the animals were divided into
two groups for extinction. The control group ran to the goal box
associated with reward whereas the experimental group ran
to the one associated with non-reward. Extinction was signifi-
cantly slower for the experimental group running to the unre-
warded box than for the control group running to the rewarded
one. Elam, Tyler, and Bitterman (1954) confirmed these re-
sults in a second study using spaced trials during both training
and extinction. Thus, on the basis of these studies there is evi-
dence that attractions do develop in the goal box during a zero
reward schedule.

The results of these studies by Bitterman and his colleagues
seemed to offer such dramatic support for dissonance theory
that it appeared worth while to confirm and extend them. As a
first step, we replicated the second of the above studies, using
more widely spaced trials, a slightly shorter runway, and a larger
number of training trials. Ten animals were run in each extinc-
tion condition. Our results showed that both groups took equally
long to extinguish. There was no indication of a significant dif-
ference between them. We repeated our study with 20 more
rats and again got the same outcome. Thus, our own results are
more in line with those reported by Marx (1960). Although
our studies indicated that zero reward produces effects on ex-

THE EFFECTS OF ZERO REWARD 107

tinction that are as strong as those ascribable to secondary re-
ward, we were unable to reproduce the dramatic difference
reported by Bitterman and his coworkers. We have no clear
explanation of this difference in outcome.

This failure to replicate a difference favoring the zero re-
ward group is bothersome. Clearly, it would be valuable to con-
struct an experimental situation in which the Bitterman result
could be produced with greater stability. In an attempt to do
so we decided to compare two independent groups both volun-
tarily going to a given place. One of these groups would always
be rewarded, while the other would never be rewarded. There
is, of course, an obvious technical problem that must be solved
in order to do such an experiment: How can one design a pro-
cedure that will induce an animal to continue engaging in an
action for which it has never been rewarded and for which it
never is rewarded? One could, of course, force the animal by
physically pushing it or by compelling it to engage in the ac-
tivity in order to avoid some noxious stimulation. But neither
of these procedures satisfies our requirements. In the former
case the animal is not voluntarily engaging in the activity, and,
in the latter case, escaping the noxious stimulation is every bit
as good as being rewarded. The technical problem does not, in
this form, really seem capable of solution. To require an animal
to perform an act for no reason whatsoever is, perhaps, impos-
sible in principle.

In order to design an experiment to meet the requirements
we have stated it is obviously necessary to make some compro-
mises. The compromise we decided on, which would allow us
to solve the technical problems and still obtain data that were
meaningful with respect to the question of zero reward, was to
use a variation of a delay of reward experiment. Animals could
be run under conditions of delay that is, on every trial they
would be delayed for a period of time in a mid-box before being
allowed to continue to an end box where food would be ob-
tained. One could then test, during "extinction/ 3 ' their willing-
ness to continue running just to the mid-box, a place where they
had been delayed en route to food and never rewarded.

From the existing literature, of course, we already know that

108 THE EFFECTS OF ZERO EEWAED

such delay will increase resistance to extinction when extinction
trials are run from the start box to the end box. Such data, al-
though they support the dissonance formulation, are not conclu-
sive for the question of zero reward. According to our formula-
tion, the dissonance produced by the delay experience is re-
duced in at least two ways in conjunction with the situation in
which the delay occurs, and in connection with things experi-
enced immediately after the delay. Thus, the end box has ac-
quired some extra attraction even though delay has occurred
prior to it and resistance to extinction is increased. Such results,
however, are not completely decisive for our present purposes
because, after all, the animal is demonstrating increased willing-
ness to go to a place where it has been rewarded (the end box),
and this might be the result of some interaction between the
dissonance-producing experience of delay and the reward it ob-
tains. If, however, one could demonstrate the same increased
resistance to extinction when it is running only to a mid-box, that
is, to a place never associated with reward, this would tend to
eliminate this ambiguity and to focus attention on the experi-
ence of non-reward itself.

Experiment 7. The Effect of a Zero Reward Schedule

The specific design of the experiment we conducted was as
follows. The apparatus consisted of an L-shaped runway. The
first stem, painted gray, was 4 feet 10 inches long, the first 10
inches being the start box. Spaced evenly throughout the run-
way were four 3-inch-high hurdles. This runway opened into
an unpainted mid-box, at the right rear corner of which was an
exit passage at right angles to the first runway. The second run-
way, painted black, extended for 3 feet beyond the exit passage.
No hurdles were present. It opened into a black end box, 8
inches wide, 12 inches long, and 5 inches deep dimensions very
different from those of the mid-box.

Fifty-four albino rats, half males and half females, were
tamed and then placed on a 22-hour food-deprivation schedule
which was maintained throughout the experiment. After be-
coming adapted to eating pellets of wet mash in the end box,
all animals were given 20 runs, spaced over six days, from the

THE EFFECTS OF ZERO REWABD 109

start box to the end box. During this period the hurdles were
introduced and gradually raised to full height. On these runs
36 of the animals found a pellet of food in both the mid-box and
the end box. The other 18 animals were never rewarded in the
mid-box. Instead, they were delayed there for an interval which
was gradually increased until, on the last two trials, the delay
was 20 seconds. These animals were rewarded, however, on
reaching the end box.

At this stage the 36 animals that had been fed in the mid-box
were further divided into two groups of 18 each. For the re-
mainder of their training, one of these groups, the 100 per cent
group, continued to find food in the mid-box on every trial. As
soon as they turned away from the food dish, the exit door was
opened. The other group, a 50 per cent group, found food in
the mid-box on only half the trials. On the other half, these ani-
mals were delayed there without food for 20 seconds before the
exit door was opened. The third group, a zero per cent group,
continued to be delayed in the mid-box for 20 seconds without
food on every trial. The 100 per cent and 50 per cent groups
required about 20 seconds to eat the food in the mid-box. On
these rewarded trials, the exit door was opened as soon as they
turned away from the food dish. All animals, of course, found
food in the end box on every trial. Thus, the three groups dif-
fered only in the percentage of times each found food in the
mid-box.

These training trials were given at the rate of 5 a day for 16
days. There were at least 30 minutes between each trial. Run-
ning times were taken from the opening of the start box door
until the animal entered the mid-box. At the end of training,
all groups were given extinction trials. These trials were run
from the start box to the mid-box only. In the latter, the animal
was retained for 20 seconds without food and then returned to
its home cage. If an animal failed to enter the mid-box within
120 seconds, it was taken out of the apparatus. The criterion of
extinction was 5 such trials, not necessarily consecutive. A maxi-
mum of 90 extinction trials were run at the rate of 5 a day, with
at least 30 minutes between trials. One animal in the 50 per cent
group died during training.

110 THE EFFECTS OF ZERO REWABD

From our theoretical point of view, we can summarize the
procedure as follows: The second runway, and the end box in
which all animals were rewarded every trial, can be regarded as
having nothing to do with the experiment except for providing
the conditions under which all animals would continue to per-
form the activity during training. In other words, reward in the
end box was the thing that "tricked" the zero per cent group into
continuing to respond. The experiment proper is concerned
only with the first part of the apparatus, namely, start box, run-
way, and mid-box. Confining our attention to this part of the
apparatus, our experimental procedures have produced three
groups a 100 per cent reward group, a 50 per cent reward
group, and a zero per cent reward group.

Let us look at the results. If our theory is correct, the zero per
cent group, having had the largest number of unrewarded experi-
ences, should be the slowest to extinguish. The comparison be-
tween the 100 per cent and 50 per cent groups should, of course,
show the usual effect of partial reward.

The first data that we shall examine are the average number
of trials to a criterion of extinction. It will be recalled that the
animals were removed from the apparatus if they failed to enter
the mid-box in 120 seconds. After 5 such trials, we stopped run-
ning the animal. Unfortunately, this proved to be much too
strict a criterion of extinction. After 90 extinction trials, at
which point we discontinued the experiment, there were still
several animals running. Therefore, we arbitrarily chose some
reasonable value with respect to which all animals had "extin-
guished" within the 90 trials that we ran. To be sure that the
choice of criterion did not make any essential difference, we ana-
lyzed the data with respect to a number of them and found the
results to be always approximately the same. The data shown
in Table 5.1 are based on a criterion of 5 trials in which the
animal did not enter the mid-box within 30 seconds.

A glance at the table shows that, as expected, the zero per
cent reward condition had the greatest resistance to extinction.
It takes this group an average of 43 . 6 trials to reach the criterion
of extinction as compared with 37.1 trials for the 50 per cent
reward group and only 28.4 trials for the 100 per cent reward

THE EFFECTS OF ZERO KEWABB 111

TABLE 5.1

RESISTANCE TO EXTINCTION FOR DIFFERENT
PERCENTAGE OF REWARD GROUPS (EXPERIMENT 7)

Experimental Average Number

Group N of Trials to Extinction

100% Reward 18 28.4

50% Reward 17 37.1

0% Reward 18 43.6

group. The averages of the 100 per cent reward group and the
50 per cent reward group are significantly different at the . 02
level of significance. In other words, we do get the usual partial
reward effect on resistance to extinction. The difference be-
tween the 50 per cent reward and zero per cent reward groups
is significant at the .05 level. This seems to be sufficient demon-
stration that additional unrewarded experiences in a place in-
crease the magnitude of extra attractions, and hence resistance
to extinction, even if the place is one where the animal has never
experienced any extrinsic reward.

The data on running time during extinction show the same
effects. Figure 5 . 1 presents the average running times on the
last day of acquisition and the first ten days of extinction. It will
be noticed that the 100 per cent reward group extinguishes most
quicHy and the zero per cent reward group is most resistant to
extinction.

There is, however, some point in examining these data on
running times during extinction somewhat more closely. First of
all, it is clear that the three groups of animals are not running
equally fast at the end of the acquisition period. The 100 per
cent reward animals have an average ranning time of 1.9 sec-
onds, the 50 per cent reward animals have a time of 2 . 3 seconds,
and the zero per cent reward animals have a rather long running
time an average of 4.2 seconds. These times are, of course,
quite reasonable and consistent with the previous data we have
presented for partial reward situations.

For the first two days of extinction there is not very much
difference among our three experimental conditions, but after
the second day the differences become very clear. The 100 per

112 THE EFFECTS OF ZERO REWABB

40

100% reward
o 50 % reward

x Zero% reward

c
o
a

O

I 20

ir

UJ

o 10

(T
UJ

Last day j 23456789 10

of Acq.

DAYS OF EXTINCTION ( 5 TRIALS PER DAY)

FIG. 5. 1. RATE OF EXTINCTION FOR 100 PER CENT, 50 PER CENT, AND
ZERO PER CENT REWARD GROUPS (EXPERIMENT 7)

cent reward group slows considerably in a rather short period of
time. By the fifth day this group has reached, and thereafter
maintains, a relatively slow running speed. The 50 per cent re-
ward group does not slow down so quickly; particularly on the
third and fourth day of extinction it runs very much faster than
the 100 per cent reward group. By the sixth day of extinction,
however, the difference between these two groups has vanished.
The zero per cent reward group, on the other hand, shows a
more lasting effect. Consistent with its performance at the end
of acquisition, this group starts off running more slowly than
the others. By the third extinction day, however, its curve has
crossed that for the 100 per cent reward animals, and by the
fifth day has crossed that for the 50 per cent reward animals.
These zero per cent reward animals show a very slow increase
in running time. Certainly, there is no question about the
greater resistance to extinction of those animals that are running
to a place where they have never been rewarded.

THE EFFECTS OF ZERO REWAKD 113

These results, comparing a zero reward schedule with other
reward schedules and using independent groups, are clear and
unambiguous. They fit well with our contention that the crucial
variable in prolonging extinction after partial reward is the
number of unrewarded trials. The effect does not seem to be
dependent upon any interaction between reward and non-re-
ward experiences in the same place. At the same time, these
results indicate that the same explanation we have used for par-
tial effects also accounts for delay of reward effects. The design
we used in this experiment is a natural extension of a delay of
reward experiment. We have merely separated the place asso-
ciated with delay from the place associated with reward, and
then shown that the former has acquired a positive incentive
value. All of this fits in neatly with a dissonance interpretation.

It may have occurred to the reader that the results of this
zero reward experiment, considered in isolation, can be inter-
preted in terms of similarity between acquisition and extinction
conditions. After all, this similarity is greatest for the zero per
cent reward group and least for the 100 per cent reward group.
However, these results must not be considered alone and apart
from other findings. It must be remembered that the results of
Experiment 5, on the cumulative aspects of dissonance reduc-
tion, demonstrated unequivocally that similarity between ac-
quisition and extinction conditions is not an important variable
in increasing resistance to extinction. Once having disposed of
this variable, we certainly do not want to revive it. We should,
of course, like to have a unitary explanation for all the relevant
data.

There is, however, a possible alternative explanation that we
should consider seriously at this point. This comes from the
theory proposed by Amsel (1958), who hypothesizes that frus-
tration results in increased drive. He, and others, have pre-
sented data demonstrating that after the frustration of not hav-
ing been fed when expecting food, the organism reacts with
intensified vigor. The usual type of situation in which this find-
ing has been reported closely resembles the experiment we have
described in this chapter. There are usually a start box, alley,
mid-box, second alley, and end box. The animals are trained

114 THE EFFECTS OF ZERO REWARD

to run to the mid-box, eat, then run to the end box and eat again.
There are usually two groups, which are treated differently.
One group continues to find food in both boxes whereas the
other finds food in the mid-box only on some of the trials. The
finding is that, after an unrewarded mid-box experience, the
animal runs faster in the second alley.

If one accepts this finding, which has been reported suffi-
ciently often so that it is undoubtedly correct, and if one accepts
frustration as the explanation, the question arises of whether
the phenomenon of increased resistance to extinction could be
the result of the same increased vigor following frustration. For-
tunately, the theory of frustration drive as stated by Amsel is
specific enough to allow us to answer this question. According
to his formulation, frustration is aroused if the animal expects
food and does not obtain it. Thus, according to his theory, an
animal that is partially rewarded in the mid-box experiences
frustration, but an animal that is never rewarded in the mid-box,
and consequently has never learned to expect food there, does
not experience frustration and should show no increased vigor.

There is a very nice experiment by Wagner (1959) which
tests this implication of the Amsel formulation of frustration
drive. In this experiment Wagner used the usual type of appa-
ratus described above. He ran three groups of animals, a group
that was always rewarded in the mid-box, a group that was par-
tially rewarded in the mid-box, and a group that was never
rewarded in the mid-box. In other words, the three groups that
he ran exactly parallel our three groups in the experiment we
described in this chapter.

The most important measure that Wagner obtained in his
experiment was the one customarily used in relation to Amsel's
theory, namely, speed of running the second alley. His findings,
comparing the 100 per cent mid-box reward group and the par-
tial mid-box reward group, wholly confirm earlier work on this
effect. On rewarded mid-box trials the partial reward group ran
the second alley at about the same speed as the 100 per cent
reward animals, but on unrewarded mid-box trials it ran faster
in the second alley. The results that Wagner obtained for his
zero reward group are also consistent in every way with AmseFs

THE EFFECTS OF ZERO REWARD 115

theory: the zero reward group, never having experienced the
frustration of expecting food and not obtaining it in the mid-
box, does not run faster in the second alley.

At the same time that this study confirms the theory of Amsel
in relation to what does and does not arouse frustration, it also
makes it impossible to use that same theory to explain the in-
creased resistance to extinction in the experiment we reported
in this chapter. It will be recalled that in our experiment the
zero per cent reward group showed the greatest resistance to
extinction, and the 50 per cent reward group showed results
midway between the zero and 100 per cent reward groups. In
other words, if frustration and frustration drive were causing
the increased resistance to extinction, one would have to main-
tain that the zero per cent reward group experienced the great-
est amount of frustration and had the strongest frustration drive.
The Wagner experiment shows clearly, however, that a zero per
cent reward group experiences no frustration and shows no frus-
tration drive in the Amsel sense. Thus it is clear that these two
phenomena, namely, greater speed of running in the second
alley after non-reward and greater resistance to extinction after
unrewarded experiences, cannot possibly be explained by the
same theory.

In summary, we have shown that a mixture of rewards and
non-rewards is not necessary for the partial reward effect on
resistance to extinction. The number of unzewarded experi-
ences is crucial, and a zero per cent reward schedule is > of course,
maximally effective in prolonging extinction.

In designing our_zero reward .experiment jp.order A ,to moti-
vate the animals to run, a delay, of reward situation was em-
ployed. It is clear that delay of reward has the same cumulative
effects as partial reward, which dissonance theory would imply.

Our experimental findings, in conjunction with those re-
ported by Wagner (1959), have enabled us to rule out AmseFs
frustration theory as a possible explanation for increased resist-
ance to extinction. Of course, we have not ruled out all possible
theoretical formulations using the concept "frustration/* The
only thing one can do is to examine any specific formulation of
"frustration" as it is offered.

6

The Effect of Weak Drive States

The present dissonance reduction explanation of prolonged ex-
tinction effects implies certain suggestions about the role of
motivation. Let us review, briefly, what was said about moti-
vation in Chapter 2. The dominant drive of the animal during
acquisition was said to determine, in part, the amount of disso-
nance experienced and also, in part, the extent to which this
dissonance can be reduced by finding extra attractions in the
situation.

The strength of motivation during acquisition determines
the importance to the animal of the consequences of its action.
We have said that if a hungry animal performs an act and is
rewarded with food, the action and its consequence are conso-
nant with each other. The weight, or importance, this consonant
relationship has in determining the animal's behavior depends,
however, upon the strength of its motivation: if the animal
is very hungry, this consonant relationship has considerable
weight, but if the animal is less motivated, it has correspond-
ingly less weight. This assumption is, of course, much the same
as that underlying most theories of learning, It implies that the
animal is more willing to run when highly motivated. In the
present context, however, motivation also has an effect in de-
termining the amount of dissonance that is aroused when the
consequences of an action fail to justify it. For instance, if an
animal performs an act in order to obtain food and fails to find
food, it will have experienced more dissonance if it is highly
motivated than if it is only slightly so. Thus, in a partial reward

THE EFFECT OF WEAK DRIVE STATES 117

situation, for example, the amount of dissonance aroused on an
unrewarded trial is a direct function of the degree of hunger
motivation. This in turn determines the pressure on the animal
to reduce the dissonance through the discovery of extra attrac-
tions in the situation. Consequently, the stronger the dominant
motivation the greater is the pressure to discover extra attrac-
tions in the situation whenever dissonance is aroused by absence
or delay of reward.

We also attributed a second function to the dominant moti-
vation. Largely on intuitive grounds, we assumed that the
stronger the dominant motivation, the harder it would be for
the animal actually to discover extra attractions in the situation
that would justify its behavior. It will be remembered that these
extra attractions satisfy subordinate motivations the animal may
have at the time dissonance is aroused. The ease with which the
animal can discover such attractions will therefore depend, in
part, on the number and strength of these subordinate motiva-
tions. In light of what is known about drive interactions, it
seems reasonable to assume that subordinate motivations would
be weaker and less salient if the dominant motivation were very
strong than if it were weak. T$e thus^come JoJ^gjcond^ion Jlaat ,
whereas the pressure to find exSa"attractions increases with in-
creasing motivation, the possibility of finding them decreases.
In the remainder of this chapter we shall present experimental
evidence relevant to the effect of different levels of motivation.

The Effect of Weak Motivation During Acquisition

Itjs clear from the above review of how motivations interact
with dissonance and dissonance reduction that two opposing
processes occur during acquisition for partially rewarded qid-
mals. If the dominant motivation is strong, there is considerable
dissonance but poor dissonance reduction; if the dominant mo-
tivation is weak, there is less dissonance but good dissonance
reduction.

Despite this ambiguity resulting from the presence of two
counteracting processes, we can statj^on^dear unpHcation from
dissonance theory: raising >x, lowering the level ^motivation
during acquisition should have no appreciable effect on the

118 THE EFFECT OF WEAK BBIVE STATES

difference in resistance to extinction between a 100 per cent re-
ward group and a partial reward group. In other words, we are
inclined to expect that partial reward should lead to increased
resistance to extinction even under conditions of minimal moti-
vation. Because there were no data available on this point, we
carried out a small experiment to test whether or not the partial
reward effect would be obtained when animals were weaHy
motivated during acquisition,

Experiment 8.- Partial Reward Effects Under Weak Motivation

Twenty-four rats, half of them males and half females, were
used in this study. After being tamed, they were placed on a
22-hour food-deprivation schedule. During the next 5 days they
were given preliminary training in an apparatus consisting of a
4-foot alley containing three hurdles, each 3 inches high, spaced
at equal distances in the alley. In preliminary training they were
accustomed to miming the alley and finding, in the goal box, a
sugar-coated pellet of breakfast food. During these trials the
hurdles in the alley were gradually raised to their full height.

After preliminary training, all animals were taken off their
deprivation schedule and given continuous access to regular
laboratory food pellets in their home cages. This continued
throughout the rest of the experiment. Thus, the only motiva-
tion the animals had during training and extinction was based
on their liking for the sugar-coated pellet over and above any
need for food. This was considered to be a minimal level of
motivation, for the animals were certainly never hungry.

After an intervening 2-day period, the animals were divided
into two groups, equated on the basis of their preliminary run-
ning times. All animals were then given 6 trials a day, spaced
at least 15 minutes apart, for the next 20 days. One group was
run on a 100 per cent reward schedule and the other on a 50
per cent reward schedule. On unrewarded trials, the 50 per cent
reward animals were left in the goal box for 20 seconds. Two
animals in each group were eliminated during training because
of continued refusals to run or to eat, leaving only 10 animals
in each group. All animals were then given extinction trials
spaced at least 15 minutes apart. The criterion of extinction

THE EFFECT OF WEAK DKIVE STATES 119

employed was three trials, not necessarily consecutive, on which
the animal failed to enter the goal box within 180 seconds. On
all other trials they were left in the goal box for 20 seconds.

On the last day of training, the 100 per cent reward group
averaged 4 . 7 seconds per trial and the 50 per cent reward group,
8 . 1 seconds. These are relatively slow times for this apparatus
and were to be expected under such low motivation conditions.
Nonetheless, each of these animals ate the pellet each time it
was available during acquisition. It should also be noted that
the difference in times is in the same direction and of the same
relative magnitude as that usually found in contrasts between
continuously and partially rewarded animals.

The partially rewarded group proved more resistant to ex-
tinction. The number of trials to the criterion of extinction was
24.9 trials for the 100 per cent reward group and 32.5 for the
50 per cent reward group, a difference that is significant between
the .05 and . 10 levels. It is clear that the partial reward effect
is found even though a minimal level of motivation is present
during acquisition and extinction. Thus, we have some evidence
for the notion that, even though very little dissonance was ex-
perienced on unrewarded trials, it was relatively easy for the
animal to reduce it under conditions of low motivation.

It is convenient, at this point, to examine the implications of
these data for theories which depend heavily on the unpleasant
or frustrating aspects of unrewarded trials, to which, during the
course of acquisition, the animal "adapts" in one way or another.
Such theories should anticipate that, under very weak motiva-
tion, the partial reward effect would disappear or, at least, be
greatly reduced, since an unrewarded trial cannot be very un-
pleasant when the animal is not hungry. If there is little unpleas-
antness, it is difficult to see how "adaptation" to such unpleas-
antness can help increase resistance to extinction.

The experiments to be reported next, using strong motivation
during acquisition and weak motivation during extinction, also
pose problems for these other theories. If the "adaptation" to
frustration during acquisition is a major process, then it is not
immediately clear why it should affect extinction behavior when
the animal is not hungry and, hence, is no longer suffering the

120 THE EFFECT OF WEAK DRIVE STATES

same frustrations. Thus, although our data seem to fit in well
with the theory concerning the development o extra attractions,
they seem to provide difficulty for some alternative interpreta-
tions.

The Efect of Weak Motivation During Extinction

Although, as we have seen, there is ambiguity concerning the
effects of motivation variation during acquisition, there are clear
implications concerning the effects of differences in motivation
during extinction. We can expect that the influence of extra
attractions will tend' toBe more pronounced when extinction is
run under conditions of low motivation than when it is run under
conditions of high motivation. The basis for this expectation
can be described briefly.

Suppose two groups of animals are trained under high moti-
vation, one with a 100 per cent reward schedule and the other
with a partial reward schedule. Suppose, further, that the moti-
vational level is reduced to a minimum in both groups before
extinction is run. The 100 per cent reward group should still
extinguish fairly rapidly. The reduction in motivation should
decrease its willingness to run in search of a food reward, and
the absence of any extra attractions for this group means that
it has little other incentive for running.

According to our formulation, however, the picture for par-
tially rewarded animals should be considerably different. The
reduction in motivation should, of course, decrease their initial
willingness to run, just as for 100 per cent reward animals, but
it must be remembered that part of the incentive for these ani-
mals is the extra attractions they discovered during acquisition
satisfiers, as it were, for subordinate motivations. Consequently,
as long as the situation is not changed and as long as these sub-
ordinate motivations continue to operate during the extinction
trials, these animals have some justification for running. In other
words, the extra attractions which have been built up through
dissonance reduction tend to form an intrinsic and stable group
of incentives for the animal.

Remembering that (1) because of low motivation, the par-
tially rewarded animals would experience minimal dissonance

THE EFFECT OF WEAK DBIVE STATES 121

during the extinction trials, and remembering also that (2) they
have some justification for running because of the extra attrac-
tions they have developed in the situation, one is led to an
interesting implication. It is conceivable that these animals
would show little if any evidence of extinction except for the
initial decrease in willingness to run. This possibility was so
intriguing that it was well worth checking.

Experiment 9. Comparison of Zero and Continuous Reward
Groups Extinguished Under Low Motivation

We designed an experiment to see (1) whether a partially
rewarded group persists longer than one that has been continu-
ously rewarded, both trained when hungry but extinguished
under minimal motivation, and (2) whether, under these con-
ditions, a partially rewarded group shows any evidence of an
extinction process. Two groups of animals were trained under
the usual motivational conditions, one with continuous reward
and the other with zero reward the latter, of course, represents
the extreme of a partial reward schedule. We then tested both
of them on extinction trials while they were not hungry.

The procedure that we employed was an exact repetition,
using the same apparatus, of the acquisition conditions of Ex-
periment 7, described in Chapter 5, for two of the three groups
of that study, namely, the 100 per cent and the zero per cent
reward groups; the 50 per cent reward group of the previous
experiment was not duplicated in the present one since it was
felt to be unnecessary. To remind the reader, the procedure was
briefly as follows. All animals ran from the start box to a mid-
box on every trial, and then to an end box, where they were
rewarded on every trial. The 100 per cent reward group was
also rewarded on every trial in the mid-box. The zero per cent
reward group was never rewarded in the mid-box but was sim-
ply delayed there for a time equal to the time spent eating by
the other group.

After the acquisition period was finished, the procedure of
the present experiment diverged somewhat from that of the
previous study. The difference stemmed from our attempt to
make the animals relatively uninterested in food during the ex-

122 THE EFFECT OF WEAK DKIVE STATES

tinction trials. After the last acquisition trial a plentiful supply
of dry pellets was put into the cage of each animal, and there-
after in the experiment, food was always present in the home
cage. In addition, the animals were not run on the next two days
to make sure that, before extinction began, they would get off
the hunger rhythm to which they had become accustomed and
would recover much of the weight they had lost.

Also, during the two days on which the animals were not
run in the apparatus, an attempt was made to communicate to
them that food was no longer available in the end box. Specifi-
cally, on each of these days each animal was put into the end
box four different times and allowed to remain there without
food for one minute. One may assume that this kind of proce-
dure is at least somewhat effective in communicating to rats
that food is no longer available: experiments on so-called 'latent
extinction" (Eamble, 1961, pp. 320-23) have shown that this
kind of treatment does result in more rapid extinction. To the
extent, then, that this procedure was effective, it indicated to
the animals in the zero reward group that food was no longer
available in the apparatus, and, to the 100 per cent reward group,
that food was no longer available at least in the end box. To
summarize: by the time the extinction trials were begun each
animal had had two days during which food was always avail-
able in its home cage and had also had eight one-minute place-
ments in the end box with no food there. We thus hoped that
during the extinction trials the animals would have relatively
little motivation for food in the experimental apparatus.

Just as in the preceding experiment, extinction trials were
run from the start box to the mid-box. After a period of 20 sec-
onds in the mid-box the animal was removed to its home cage.
Three trials were run on each day. If an animal did not enter
the mid-box in 120 seconds, it was removed from the runway.
All animals were run on every trial regardless of how many times
they refused to enter the mid-box. After 60 trials of extinction
the experiment was discontinued. Fourteen animals were run
in each of the two conditions in the experiment.

As one would expect, there was a difference in running times
between the two groups of animals at the end of the acquisition

THE EFFECT OF WEAK DRIVE STATES

123

period. The zero reward group ran much more slowly than the
100 per cent reward group. The mean running times at this
point in the experiment are almost identical with the compar-
able figures for the experiment reported in Chapter 5. The 100
per cent reward group had an average running time of 1 . 8 sec-
onds whereas in the previous experiment it was 1.9 seconds.
The comparable figures for the zero reward groups are 4.6 sec-
onds in this experiment and 4.2 seconds in the preceding one.
This similarity of the figures between the two experiments is,
of course, expected since the procedure during acquisition was
identical. Nevertheless, it is comforting to have data showing
that the identical procedure did indeed produce comparable
results.

Let us now turn our attention to the data obtained during
extinction, which are presented in Figure 6.1. The average
miming times during extinction, even on the first few trials, are
not at all comparable to the times at the end of acquisition. This
is, of course, to be expected, since the animals were hungry
during acquisition and were not at all hungry during extinction.
Consequently, both groups run much more slowly at the be-
ginning of extinction. Consistent with the direction of the dif-

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100 % reward

1,2 3,4 5,6 7,8 9,10 11,12 13,14 15,16 17,18 19,20

PAIRS OF DAYS DURING EXTINCTION (3TRIALS PER DAY)
FIG. 6 . 1. EXTINCTION UNDER Low MOTIVATION (EXPERIMENT 9)

124 THE EFFECT OF WEAK DRIVE STATES

f erence in running speeds at the end of acquisition, the 100 per
cent reward group runs much faster than the zero reward group
on these initial test trials. The figures are 7 . 6 seconds and 17 . 8
seconds, respectively, for the average on the first two days of
extinction. This difference is significant at the .01 level of sig-
nificance.

Thereafter, however, the course of events is interesting. As
the figure shows, the 100 per cent reward group has the usual
curve of extinction for the first 10 or 12 days. Its average run-
ning speed becomes slower and slower. The zero reward group,
however, shows a most unusual effect. On the third and fourth
days it actually runs somewhat faster than it did on the first
two days, although not significantly so. The important point is
that there is no evidence of any slowing down for the first eight
days. On the ninth and tenth days these animals are still run-
ning almost as fast as they were on the first two days. By the
tenth day the zero reward group is running faster than the 100
per cent reward group, a difference significant at the .06 level.
In other words, for the first 30 extinction trials, the difference in
performance between the two groups is noticeably marked.
Removing the drive for food does not seem to have had any
great effect during these trials on the usual shape of the extinc-
tion curve obtained from a continuously rewarded group. For
the zero reward group, however, the removal of the hunger drive
has virtually eliminated any evidence of extinction for this pe-
riod.

It should be emphasized that the curves for the two groups
cross. The zero per cent reward group starts extinction with
slower and ends with faster running times than the 100 per cent
reward group. After the crossover, the former runs significantly
faster than the latter group. Clearly, the zero per cent reward
group are not performing at some unmotivated "operant" level.
There must be some directed motivation which leads them to
be consistently and significantly faster than the 100 per cent
reward group.

It is clear from these data that our expectations are con-
firmed. Animals trained under a zero reward schedule persist
longer than continuously rewarded ones even though both are

THE EFFECT OF WEAK DRIVE STATES 125

extinguished under conditions of minimal motivation. We
seem to be justified in concluding that extra attractions continue
to operate in the absence o the motivation that was dominant
during training.

The evidence for the possibility that the zero reward group
would show little if any indication of extinction is more compli-
cated. During the first 24 trials these animals show a relatively
weak but consistent willingness to run. There is no evidence of
an extinction process for them during this period. All of this
looks quite favorable to our supposition. But then, unfortu-
nately, the next 12 trials provide clear evidence of decreased
willingness to run. This should be decisive, except for the queer
behavior shown in Figure 6.1 from the thirteenth day on. The
zero reward group begins to run faster each day, until by the
twentieth day its average running time is shorter than on the
first day of extinction. This phenomenon is clearly much more
than we bargained for, but obviously it invites speculation con-
cerning dissonance reduction processes during extinction. Be-
fore indulging in speculation of this nature, however, the better
part of valor indicates that we should try to replicate this out-
come. This is especially necessary when it is observed that the
continuously rewarded animals show the same increase in will-
ingness to run, a result that we had no reason to expect.

Experiment 10. Comparison of Zero and Continuous Reward
Groups: A Replication of Experiment 9

The training conditions in this study were in every way iden-
tical to those described in the previous experiment. There were
12 animals in each group. The same apparatus, the same drive
level, the same trial spacing, and the same number of trials were
used. Again, both the 100 per cent and the zero reward groups
found food in the end box on each trial, but whereas the 100 per
cent reward group also found food on each trial in the mid-
box the zero per cent reward group was simply detained there.
Again, in the two days between acquisition and extinction, the
animals had food always available and were given eight "latent
extinction" trials in the end box.

On the last day of acquisition, the average running time for

126 THE EFFECT OF WEAK DRIVE STATES

the 100 per cent reward animals was 1 . 7 seconds and for the
zero per cent reward animals, 4.4 seconds. These times are
strictly comparable to those obtained in Experiments 7 and 9.
The results of the extinction trials for this replication are shown
in Figure 6 . 2. Here the average running times are again plotted
for blocks of six trials or two days.

The most obvious result is that, again, zero per cent reward
animals tend to persist longer during extinction than the 100
per cent reward animals. They start out more slowly than the
100 per cent reward group, but on the last few days of extinction
run faster than the other group. These differences, although not
statistically so significant as those in Experiment 9, clearly sup-
port the findings of the previous study. Also, as in the previous
experiment, the 100 per cent reward group shows an extinction
curve. There is a progressive slowing up throughout the 60
trials. The curve of the zero per cent reward group, however,
is rather distinctive: despite wide and unexplained daily varia-
bility, there is, for the zero reward group, no apparent progres-
sive trend in the running times. Instead these animals, with the
exception of days 5 and 6, maintain a fairly uniform running time
throughout the 20 days of extinction.

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1,2 3,4 5,6 7,8 9,10 11,12 13,14 15,16 17,18 19,20

PAIRS OF DAYS DURING EXTINCTION (3 TRIALS PER DAY)
FIG. 6.2. EXTINCTION UNDER Low MOTIVATION (EXPEEIMENT 10)

THE EFFECT OF WEAK DRIVE STATES 127

This behavior was also characteristic of the zero reward ani-
mals in the previous experiment, at least during the initial stages
of extinction. In that experiment, these animals slowed down
somewhat, but this was followed by subsequent improvement
in running speed so that, at the end of extinction, they were run-
ning just as fast as before. In retrospect, one is tempted to in-
terpret the peak at days 11 and 12 in Figure 6 . 1 as the same type
of variability in daily performance that is obvious in the present
experiment.

Since our procedure was identical for the two experiments,
perhaps the best picture of the results may be obtained by com-
bining the data, as shown in Figure 6.3. It seems clear that the
100 per cent reward group does, and the zero reward group does
not, show evidence of extinction.

There is, then, evidence to support the following suggestions.
Animals that have low motivation during extinction experience
little dissonance during such trials. The failure to find food
no longer has any real importance for them. At the same time,
for animals that have previously experienced and reduced dis-
sonance, subordinate motivations are still active so that the

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100 % reward

1,2 3,4 5,6 7,8 9,10 11,12 13,14 15,16 17,18 19,20

PAIRS OF DAYS DURING EXTINCTION (3 TRIALS PER DAY)

FIG. 6 . 3. COMBINED RESULTS FOR EXTINCTION UNDER Low MOTIVA-
TION (EXPERIMENTS 9 AND 10)

128 THE EFFECT OF WEAK DRIVE STATES

extra attractions in the situation provide some justification for
running. As long as these attractions remain stable, the ani-
mals show a weak but continued willingness to perform.

Further Evidence for the Development of Extra Attractions

The procedures and results of the series of experiments pre-
sented earlier in this chapter suggested to us a way of designing
a study that could more effectively support our theory concern-
ing the development of extra attractions. These previous studies,
which contrasted 100 per cent reward groups with zero per cent
reward ones, provide some evidence that the extra attractions
developed through dissonance reduction are associated, at least
in part, with the place where dissonance was experienced. Of
course, we assume that such attractions have also developed with
respect to the activity involved and other aspects of the appara-
tus as well. But the results obtained when extinction trials were
run from the start box to the mid-box imply that a considerable
part of these attractions is concentrated in the area of the
mid-box.

There is always the possibility, however, that the superiority
of the zero per cent rewarded mid-box stemmed from some other
aspect of the procedure. After all, the 100 per cent reward ani-
mals have been treated very differently from the zero per cent
reward ones. To us this represents a difference in magnitude of
dissonance, but other theorists might wish to interpret it differ-
ently. If, however, we could compare two groups with identical
experience, that is, two zero per cent reward groups that differed
only in the place where they experienced dissonance, we could
make alternative interpretations less plausible. If each group
preferred the place where it had experienced delay, this would
strongly support our interpretation.

Such data could be collected with a preference test based
upon the experimental procedures used in the mid-box studies
reported earlier. The experimental design needed is as follows.
Two groups of zero reward animals are trained in the same
apparatus. One is delayed on each trial at a definite point on its
route to the goal box. The other is similarly delayed on each
trial, but at a distinctively different point in the apparatus. Each

THE EFFECT OF WEAK DRIVE STATES 129

group should experience the same magnitude of dissonance and
dissonance reduction as the result of the delay, but the extra
attractions that develop should be largely associated with the
stimuli characteristic of the delay place. Consequently, if the
two groups are then given an opportunity to choose between
these two delay places, each should show a preference for the
one at which it had been delayed. Remembering our findings
with conditions of low motivation during extinction, we thought
these preferences would be somewhat more striking if the test
trials were run with minimal motivation. Consequently, we de-
signed and ran a new study.

Experiment 11. A Comparison of Two Zero Reward Groups

The apparatus employed consisted of three runways, an end
box, and two distinctive delay chambers. The first runway,
painted gray, was 30 inches long. It led to the first delay cham-
ber, which was 12 inches long, 12 inches wide, and 5 inches
deep; it, too, was painted gray. There were guillotine doors at
both the entrance and exit. This exit opened into a second run-
way, 48 inches long, painted white; it contained three evenly
spaced hurdles, 3 inches high. This runway, in turn, opened
into a second delay chamber. This was an unpainted box, 12
inches wide, 14 niches long, and 21 inches high, with an exit at
the right rear corner. There were guillotine doors at both the
entrance and exit. The exit opened into the third runway, at
right angles to the second runway, which was 46 inches long and
painted black. The last 10 inches formed the end box.

After taming and several days on a hunger schedule during
which they had food available for two hours a day, the animals
were given experience eating wet mash pellets in the goal box.
They were then given 12 rewarded runs through the apparatus
with all doors open. During the last 6 of these the hurdles were
introduced and gradually increased in height to 3 inches. This
preliminary training was spread over 6 days.

The animals were divided into two groups of 15 each. For
the next 18 days both groups were run 4 trials a day with at least
30 minutes between trials. The only difference in procedure for
the two groups was as follows. Delay Group 1 was delayed in

130 THE EFFECT OF WEAK DRIVE STATES

the first delay chamber. At the time these animals entered it
from the first runway, the exit gate was closed. The entrance
door was closed after them. After a prescribed delay period the
exit door was opened. These animals were never delayed in the
second delay chamber. The animals in Delay Group 2, on the
other hand, were never delayed in the first delay chamber, but
they were held in the second delay chamber for an equal length
of time before being released. During the first 10 training trials,
this delay interval was gradually increased from 2 to 20 seconds
and was kept at 20 seconds thereafter. All animals were re-
warded on each trial with a wet mash pellet in the end box. One
animal in Delay Group 1 died during training.

At the end of training, an ample supply of dry pellets was
given each animal and thereafter food was continuously avail-
able. During the next 2 days, the animals were not run. Instead,
each day they were placed in the end box without reward for
four one-minute periods. Thus, at the beginning of extinction,
all animals were under low food motivation and had had "latent
extinction" experiences in the apparatus.

Extinction trials were then started and were given at the
rate of 3 a day, with at least 30 minutes between trials. On these
trials, the animal was placed directly in the first delay chamber,
the exit door was then opened, and it was permitted to run the
second alley and enter the second delay chamber. If it did so,
the animal was retained there for 20 seconds and then returned
to its home cage. If, instead, the animal retraced, and re-entered
the first delay chamber, it was retained there for 20 seconds and
then removed from the apparatus. If an animal did not enter
the second delay chamber, or had not retraced to the first one,
within 120 seconds, it was removed from the apparatus. Each
animal was run on every trial. Clearly, the procedure we em-
ployed here was an attempt to combine a preference test be-
tween the two delay boxes and an extinction test in which we
could record running speeds. This naturally introduces some
problems with which we shall have to cope as they come up in
presenting the results. This procedure of permitting the animals
to return to the first delay box was maintained for 10 days, that
is, 30 trials. The procedure was then changed to resemble usual

THE EFFECT OF WEAK DRIVE STATES 131

extinction trials more closely. For another 10 days extinction
trials were run from the first to the second delay box without
permitting retracing. After the animals left the first delay box
(which was the start box during extinction ) the door was closed
and they were not permitted to return to it.

Let us first look at the data relating to preferences between
the two delay boxes. Group 1, it will be recalled, was delayed
in the first delay box, and Group 2 was delayed in the second.
If each of these groups has now developed some attractions in
the place where it was delayed, we should expect a higher inci-
dence of return to the first delay box by the animals of Group 1.
The first two days of extinction show almost no returns to the
first delay box by either group of animals. Undoubtedly, it took
these 6 trials for the animals to comprehend the new situation,
to understand that they were allowed to go to the second delay
box and no farther. Starting on the third day of extinction the
two groups show differential numbers of returns to the first
delay box. On the fourth and fifth days of testing, the difference
between the two groups is large and significant. On these two
days, 10 of the 14 animals in Group 1 retrace at least once. Only
4 of the 15 animals in Group 2 do so. This difference yields a Chi-
Square of 5,65, which is significant at the .02 level. The same
difference can be seen in the average number of retracings. The
animals in Group 2 show an average of only 0.4 returns to the
first delay box on these two days, while the animals in Group 1
show an average of 1.2 returns to the place where this group
had been delayed during training. Clearly, the animals that
were delayed in Delay Box 1 did indeed prefer Delay Box 1 more
than the animals that were delayed in Delay Box 2.

After the fifth day, the difference between the two groups
had diminished, and by the tenth day it had disappeared alto-
gether. During these latter days the number of returns for the
animals that were delayed in Delay Box 2 increased, as if they
were learning that a trial could be terminated by such behavior.
Consequently, on the eleventh day we changed the procedure
so as to prevent returns and ran the remainder of the trials as
a simple extinction test.

The data comparing the two groups on miming times are

132

THE EFFECT OF WEAK DBJVE STATES

presented in Figure 6 . 4. These data are presented only for days

I and 2, on which there were very few returns to the starting
delay box ( three for Group 1 and four for Group 2 ) , and for days

II through 20, on which returns were not permitted.

On the first two days of extinction, both groups of animals
run rather slowly, undoubtedly because of the removal of the
hunger drive and also because of the unfamiliarity of the new
procedure. Never before had either of the groups of animals
been placed directly in Delay Box 1 to start a trial. On the first
two days of extinction there is a large difference between the
two groups, which is significant at the . 05 level. Group 1, which
was delayed in Delay Box 1, has an average of 28 . seconds per
trial, but Group 2, which was delayed in Delay Box 2, runs more
slowly, with an average of 38.6 seconds per trial. This initial
difference can be attributed to two factors. First of all, it reflects
differences in speed of running the alley between the two delay
boxes during acquisition. The group delayed in Delay Box 1

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o Group 2, delayed in delay -box 2

1,2

11,12 13,14 15,16 17,18 19,20

PAIRS OF DAYS DURING EXTINCTION (3 TRIALS PER DAY)

FIG. 6.4. COMPARISON OF Two DELAY GROUPS DURING EXTINCTION
(EXPERIMENT 11)

THE EFFECT OF WEAK DRIVE STATES 133

ran this alley quickly and unhesitatingly, whereas the animals
in the other group showed noticeable hesitations in the alley
before entering Delay Box 2, where they were to experience
delay. The other factor that probably contributes to this initial
difference between the groups lies in their previous experience.
Group 1, although it had never been placed directly in Delay
Box 1 to start a trial, had had the experience of waiting there
until the door opened and then running on. Group 2, on the
other hand, had never had such experience. These animals had
always run directly through Delay Box 1. At any rate, these
initial differences exist. On days 11 and 12 it is clear that the
difference in running times between the two conditions has re-
versed itself. On days 11 through 14, Group 1 runs significantly
faster than Group 2 ( .10 level). After the fourteenth day of
extinction the difference between the two groups disappears.
It is unfortunate in some ways that we did not run all 60 trials
as a normal extinction procedure, since it is impossible to know
how the last 30 trials were affected by the experiences of having
been able to return to the starting delay box. However, it is also
valuable to have the preference data that we obtained at the
beginning of the testing.

All in all, taking the choice data and the data on time of
running, it seems justified to conclude that our expectations have
been supported. Although the effects axe weak, there does seem
to be a tendency for Group 1 to prefer Delay Box 1 and for
Group 2 to prefer Delay Box 2. Group 1 is, at least, more willing
to return to Delay Box 1 and Group 2 runs more quickly to
Delay Box 2. We may say, then, that we have presented evi-
dence that at least some of the dissonance which the animals
experience during delay is reduced by developing attraction for
the specific place where they were delayed.

New Learning Based on Extra Attractions

Despite the weak effects observed in the above experiment,
we were optimistic enough to hope that these extra attractions
would be demonstrable in a test involving new learning. It was
hoped that once these extra attractions had become associated
with a given aspect of the situation, the lure of these would be

134 THE EFFECT OF WEAK DBIVE STATES

sufficiently strong to induce the animal to learn entirely new
behaviors. We therefore designed and carried out two such
studies, which are reported below. To anticipate, we had no
difficulty in obtaining clear-cut evidence of learning when the
only incentive was the opportunity to return to the place where
dissonance reduction had occurred. The great ambiguity in
each of the studies is that this learning is equally strong in both
of our comparison groups.

Experiment 12. Extra Attractions as an Incentive for Lever
Pressing

Two groups of 15 animals each were trained on the single
mid-box apparatus that was described in Experiment 9. One
group was trained on a zero reward schedule it was only de-
layed and never rewarded in the mid-box. The other was on a
100 per cent reward schedule with food available in the mid-box
on each trial. The training procedure was exactly as described
in Experiment 9, that is, the same apparatus, the same number
of trials, the same spacing, and so on. These animals also were
given two days of ad lib feeding before the test trials began; they
each had eight one-minute "latent extinction" experiences in
the end box during this period; and all continued on ad lib feed-
ing during the test trials.

For the test trials, the mid-box was removed from the train-
ing apparatus. A totally new start box was placed immediately
before the entrance to the mid-box. At the front end of this
start box was a metal pedal, one inch square, and one inch from
the floor. When this was pressed, the door to the mid-box
opened so that the animal could enter.

The procedure used in this new learning situation was as
follows. The animal was placed in the start box and remained
there until it had either pressed the pedal and entered the mid-
box or until 3 minutes had passed. If it entered the mid-box,
the door was closed and the animal was detained there for 20
seconds. If it had not pressed, or had pressed but not entered,
it was removed from the apparatus after 3 minutes. Two trials
a day were given, spaced approximately 30 minutes apart. Test-
ing was continued for 20 days.

Our expectation, of course, was that both groups would show

THE EFFECT OF WEAK DKIVE STATES 135

some initial learning of the pedal-pushing response, the 100 per
cent reward group because of secondary reward and the zero
per cent reward group because of the extra attractions that had
developed in the mid-box. We anticipated that the 100 per cent
reward group would, however, show the rapid extinction that
is usually the result when learning is based solely on secondary
reward. We expected the zero per cent reward group, on the
other hand, to learn and maintain its performance, assuming
that the extra attractions would be enduring and intrinsic to the
situation. This should be especially true when the animal has
no strong interfering drive such as hunger. What actually oc-
curred, however, was somewhat different.

On the first day, both groups took an average of about 50
seconds to press the pedal and enter the mid-box. During the
next 7 days, both groups showed continual improvement to the
point where their averages were between 12 and 15 seconds.
For the remaining 12 days of testing, they each maintained this
level, with only minor daily fluctuations and no indication of ex-
tinction. There was never any real difference in the perform-
ance of the two groups during the entire testing period.

We can assert with considerable assurance that the improve-
ment in performance observed in this test was "real" learning.
Taken alone, the behavior of the zero per cent reward group
makes a good case for the presence of extra attractions in the
situation. But the 100 per cent reward animals learn equally
well. Perhaps secondary reward was effective for this latter
group; perhaps, also, the particular task of pressing a lever to
open a door has some intrinsic interest for the white rat. Myers
and Miller ( 1954) and Seward and Procter (1960) present data
compatible with this possibility. At any rate, the only legiti-
mate conclusion that we can reach is that rats display very un-
usual behavior in this situation when they are satiated after a
period of alley running.

Experiment 13. Extra Attractions as an Incentive for Maze
Learning

In the hope of obtaining a demonstration of new learning
based on the extra attractions due to dissonance reduction which
would not be complicated by either of the above problems, we

136 THE EFFECT OF WEAK DBIVE STATES

designed and carried out a second study. Two groups of 15 ani-
mals each were trained on the same apparatus and with the
same procedure as that used in Experiment 11, the double delay
box experiment. Just as before, one group experienced an un-
rewarded delay in the first delay box and the other in the second
delay box. Thus, neither of these delay boxes should have ac-
quired any secondary reward value. On the other hand, as the
results of Experiment 11 showed, each of them had acquired
some weak extra attractions for the group delayed in it.

For a new learning task, we constructed a four-unit U-niaze.
After two days of ad lib feeding and "latent extinction" experi-
ences, both groups were run on the maze, using Delay Box 1
as the start box and Delay Box 2 as the end box. Our reasoning
was that the group that had been delayed in Delay Box 2, which
was now the end box, would have an incentive for running and
learning the maze. The other group, however, which had been
delayed in Delay Box 1 (which was now the start box), would
not. If anything, this latter group would have some incentive
for staying in the vicinity of the start box. All animals were
given 2 trials a day, spaced approximately 30 minutes apart, for
a period of 20 days. Retracing was permitted. Time and error
scores were recorded. Each animal was allowed a 3-minute in-
terval to traverse the maze and enter the end box. If it had not
done so in this period, it was removed from the apparatus.

The results of this experiment are very similar to the results
of the previous one in spite of the fact that secondary reward
considerations are absent and a quite different task was used.
Both groups, although not hungry and never obtaining food,
show clear evidence of learning. Indeed, the learning is fairly
rapid, but there is no evidence of any difference between the
two groups. The evidence for the rapidity with which learning
occurred can be seen in Figure 6 . 5, which presents, for the first
10 days of learning the maze (2 trials a day), the per cent of
runs that were errorless or showed only one error. Naturally,
this percentage is almost zero on the first day. The "chance
level" indicated in Figure 6 . 5 is computed as though the animal
ran the maze without any retracing. Clearly, with retracing per-
mitted, the animals start below this "chance level." The curve
then rises, until by the sixth day it has reached about 75 per cent

THE EFFECT OF WEAK DRIVE STATES

137

e 70
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o 60

.50

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2 .30

20

10

Group I, running away from its delay-box
o Group 2, running to its delay-box

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DAYS OF NEW LEARNING

FIG. 6 . 5. LEARNING A MAZE AFTER DELAY EXPERIENCES (EXPERI-
MENT 13)

for each of the groups. Certainly, learning has occurred and the
animals perform significantly better than "chance/* There is,
however, no consistent or significant difference between the two
groups. The same pattern of clear learning with no difference
between the two groups exists with respect to running times.

We again have good evidence of learning in non-hungry ani-
mals, even when no intrinsic reward is present. It is clear that
the outcome of this study in no way supports our assumption of
differentially located extra attractions for the two groups. Al-
though we did find evidence that such attractions exist in this
situation using extinction data, we find no such evidence in
a new learning situation. It is possible that these extra attrac-
tions have been totally confounded with other types of incen-
tive, possibly of the sort that Anderson ( 1941 ) describes under
the concept of externalized motivation.

Summary

We began this chapter with the suggestion that, according
to the implications of dissonance theory, once extra attractions

138 THE EFFECT OF WEAK DRIVE STATES

have been established, reduction of motivation should, if any-
thing, enhance the effect of these attractions on resistance to
extinction.

We have presented a number of experiments attempting to
elucidate this point. We have shown that:

1. The partial jeward effect is still obtained even though both
training and extinction occur under very low motivation.

2. When acquisition trials are run with high hunger motivation
but extinction trials are run with minimal motivation, zero
per cent reward groups show little evidence of any extinction.

3. Comparing two delay groups treated identically except for
the place where the delay occurred, we were able to demon-
strate with low motivation testing that preferences develop
for the particular place in which delay was experienced.

4. We were unable to produce evidence that extra attractions,
developed through dissonance reduction, would support the
learning of a new task when the animal is otherwise not moti-
vated.

7

Effort, Expectation, and Amount
of Reward

Thus far our discussion, and the experimental evidence, have
been concerned almost exclusively with the effects of partial re-
ward and delay of reward. It will be recalled from Chapter 2
that, according to our theoretical explanation, increased effort
expenditure would be expected to have the same kinds of effects.
That is, the more effort an animal is required to exert during
training, the more resistant to extinction should the animal be.
The information that the animal has concerning the expenditure
of energy and effort is dissonant with continuing to engage in
the action in the same way that information concerning absence
of reward, or information concerning delay, is dissonant with
continuing. The greater the effort required, the greater would
be the magnitude of dissonance, and, hence, the greater the de-
velopment of extra attraction for something in the situation in
order to reduce dissonance. Thus, greater effort requirement
would result in greater resistance to extinction.

The Direct Effect of Effort

It will be recalled from Chapter 1 that the existing evidence
supports this implication of the theory. In general, the existing
data can be summarized by saying that, if conditions during ex-
tinction are held constant, then the more effort that is required
of the animal during acquisition, the greater is its resistance to
extinction. This is reassuring data, in a sense, but a procedure
that involves differential changes for various groups between

140 EFFORT, EXPECTATION, AND REWABD

acquisition and extinction inevitably results in some ambiguity
of interpretation. It is always possible to explain the results
from such experiments on the basis of decrements or increments
of behavior resulting from changed stimulus conditions, rather
than on the basis of extra attractions that have developed in re-
ducing dissonance introduced by effort Consequently, it would
be valuable to demonstrate that increased effort during training
results in increased resistance to extinction in 100 per cent re-
warded animals even if conditions are not changed at all be-
tween training and extinction trials. Clearly, in order to produce
such results one would need a situation where, for the high effort
condition, the extra attractions that had developed would be
more powerful than the discouragement of running during ex-
tinction owing to the larger expenditure of energy needed.

We proceeded to attempt such a demonstration. In order to
do this we arbitrarily selected an activity in which the expendi-
ture of effort by the animal could be varied experimentally and
which, intuitively, seemed not to represent too strong a deter-
rent to action. Hie apparatus selected was a runway that could
be inclined at varying angles. Clearly, the steeper the slope, the
more effort would be required and the more dissonance intro-
duced on each trial. The first experiment was a preliminary one
to explore the adequacy of the situation for our purposes. One
group of animals ran a level runway during acquisition; another
group ran the runway at an angle of 45 degrees; and a third
group had variable experience that is, on some trials the run-
way was level and on other trials it was tilted 45 degrees. This
last group was run because of the possibility that such variable
experience might increase the magnitude of the effects we were
looking for: it seemed possible that high effort might introduce
more dissonance for an animal if it had a comparison with ex-
periences in which it obtained the same reward with consider-
ably less effort. The animals were extinguished under conditions
paralleling the acquisition conditions. The "level group" was
extinguished on a level runway; the "45 degree group" and the
"variable 45 degree group" were both extinguished on a 45 de-
gree runway.

The data were encouraging: The "level group" extinguished

EFFORT, EXPECTATION, AND REWARD 141

most quickly, the "45 degree group" next, and the "variable 45
degree group" least quickly. The differences, however, tended
to be slight, and because of the few animals employed and
changes in procedure which we felt were justified in a prelimi-
nary experiment, no great faith can be placed in the results.
Consequently, we do not report the experimental procedure or
the results in any detail. We were sufficiently encouraged, how-
ever, to conduct another, more adequate experiment.

Experiment 14. The Effect of Effort on Extinction with 100 Per
Cent Reward

The apparatus for the experiment was a 7-foot enclosed run-
way which could be adjusted to inclines of 0, 25, or 50 degrees.
A start box and a goal box were hinged to the runway in such
a way that they would remain level whatever the inclination of
the runway. Sixty-four naive albino rats, 32 males and 32 fe-
males, were used, all of them between 89 and 104 days old at
the start of the experiment. Two animals died during the course
of the experiment. After being tamed, the animals were put on
a 22-hour food-deprivation schedule and were adapted to eating
food pellets in the goal box. They were then divided into two
equal groups, the 25 degree incline group and the 50 degree
incline group. During the next 5 days, each group was given 8
rewarded trials of running the alley set at the appropriate in-
cline.

The animals of each incline group were then divided into
two equal subgroups. One subgroup (invariable effort) contin-
ued to receive all its trials (5 a day) at the appropriate incline.
The other subgroup (variable effort) received 3 of the 5 daily
trials at its appropriate incline and the other 2 trials with the
runway level. This training continued for 12 days, a total of 60
training trials. Trials were spaced at least 8 minutes apart.

Extinction trials were run for the next 11 days, 5 spaced trials
a day as during training. All the 50 degree animals, that is, both
the invariable and variable subgroups, were extinguished on the
50 degree slope. All the 25 degree animals were extinguished
on the 25 degree slope. No level runway trials were given dur-
ing extinction. If an animal failed to enter the goal box within

142 EFFORT, EXPECTATION, AND BEWABD

90 seconds after the start door had been raised, it was removed
from the apparatus. After an animal accumulated four 90-sec-
ond trials, not necessarily consecutive, it was considered extin-
guished and was not run any more.

The differences in resistance to extinction between the vari-
able and invariable effort subgroups, although in the same direc-
tion as for the preliminary experiment, were very slight and not
significant. For analysis and presentation of the data, therefore,
we have combined the variable and invariable subgroups, so as
to compare the low effort group (25 degree incline) with the
high effort group ( 50 degree incline ) . Since the differences that
were found between the high and low effort groups occurred
under both variable and invariable training conditions, throwing
the data together for ease of presentation seems justified.

Table 7 . 1 presents the data for the average number of trials
to reach the criterion of four 90-second trials during extinction.
The low effort group reaches this criterion in an average of 20 . 6
trials, whereas the high effort group takes 28 . 3 trials, a differ-
ence significant at the . 01 level. It should be remembered that
this difference exists even though the conditions during extinc-
tion favor the low effort group, that is, for each group conditions
during extinction are the same as conditions during acquisition.

The same differences are reflected in running times during
extinction. Table 7.2 presents these data. There is no appreci-
able difference in running times between the two groups on the
last day of acquisition. The difference that does exist, as one
might expect, slightly favors the low effort group, which has less
work to do and consequently runs slightly faster. During ex-
tinction, however, the two effort conditions quickly diverge.
During the first 5 trials on the first day of extinction the low
effort group already begins to slow up relative to the high effort

TABLE 7.1

AVERAGE NUMBER OF TRIALS TO EXTINCTION
( EXPERIMENT 14)

Number of Trials
Incline Group N to Extinction

25 degree 31 20.6

50 degree 31 28.3

EFFORT, EXPECTATION, AND BEWABD 143

TABLE 7.2

AVERAGE RUNNING TIME ON EXTINCTION (IN SECONDS)
FOR DIFFERENT EFFORT CONDITIONS (EXPERIMENT 14)

Effort Condition

25 Incline 50 Incline

(tf = 31) (N = 31)

Last day of acquisition 1.8 2.0

First day of extinction 7.1 3.8

Second day of extinction 26 . 1 16.4

Third day of extinction 37 . 2 31.0

group. This difference between the two groups persists. In
short, this is a situation where the extra attraction built up dur-
ing acquisition is sufficient to more than compensate for the
differential effort during extinction. We thus have more evi-
dence to support the theoretical implications about the rela-
tionship between effort expenditure and magnitude of disso-
nance.

Efort and Partial Reward

Granted, then, that effort does introduce dissonance and in-
creases resistance to extinction, it seems plausible to suppose
that, when added to a partial reward situation, increased effort
would augment the partial reward effect It was, of course, these
considerations which influenced the design of Experiment 5, re-
ported in Chapter 4. It will be recalled that the activity required
of the animals in that experiment was very effortful. The rats
were required to jump over two rather high hurdles and to push
under three rather heavily weighted doors in order to go from
the start box to the food compartment It will also be recalled
that, from Experiment 5, we obtained data showing that resist-
ance to extinction was a simple function of the absolute number
of times the animal experienced unrewarded trials and was not
a function of the ratio of reward during training.

After that experiment had been completed, it occurred to us
that it would be valuable to have a precise comparison between
high and low effort conditions for these data. We therefore re-
peated the experiment as exactly as we could, but with little
effort required of the animal.

144 EFFORT, EXPECTATION, AND KEWARD

Experiment 15. Cumulative Effects of Partial Reward with
Low Effort

In this low effort version of Experiment 5 the hurdles were
entirely removed from the apparatus and the doors were coun-
terbalanced to open with the slightest pressure from the animal
and to remain open after the animal pushed through. In this
way, the activity was kept much the same as that required in
Experiment 5, but the degree of physical effort the animal had
to expend was considerably reduced. Otherwise, the procedure
was identical to that in the high effort experiment. In order to
make the two experiments as comparable as possible in all de-
tails other than effort, exactly the same number of preliminary
training trials was given and exactly the same pattern of reward
and non-reward was used throughout.

Only four of the eleven experimental conditions from the
high effort experiment were repeated using low effort. One 50
per cent reward group was run for 16 unrewarded trials, and an-
other 50 per cent reward group was run for 72 unrewarded trials.
Because the high effort experiment had shown the ratio of re-
ward to be quite unimportant, we thought that these two partial
reward groups would suffice for a comparison with the high
effort experiment. The other two conditions that we repeated
using low effort were both conditions of 100 per cent reward.
One of these groups was run for zero additional trials after pre-
liminary training and the other for 54 additional trials.

The attempt to compare high and low effort conditions in
this experiment faces some methodological problems. If the two
groups that were trained with different effort requirements were
both to be extinguished with constant effort, there would obvi-
ously be a gross change in the behavior required for at least one
of the groups. We wanted to avoid the ambiguities of interpre-
tation resulting from such procedures and consequently chose
to extinguish both groups with the same effort conditions that
each had experienced during training.

This procedure, however, involved us in other, equally diffi-
cult problems. Certainly, in the low effort conditions, running
times would be faster during both acquisition and extinction.
The number of trials to a criterion of extinction would also be

EFFORT, EXPECTATION, AND KEWARD 145

greater for the low effort condition if the same criterion of ex-
tinction were to be used for both groups. Because of the obvi-
ously strong deterrent effect of a heavily weighted door, such a
difference between the high and low effort groups would exist
solely because of the effort required during extinction, regardless
of training conditions. Thus, if the same criterion of extinction
were used, conclusions concerning the effects of differential
effort during acquisition might be almost impossible. In view
of these problems, we decided to find two different criteria of
extinction which would produce roughly comparable measures
of resistance to extinction for the two effort groups. The two
conditions of 100 per cent reward in the low effort experiment
were intended to provide the basis on which we could Judge the
comparability of our measures of resistance to extinction. If we
chose criteria of extinction that made the 100 per cent reward
groups almost equal in resistance to extinction in the high and
low effort experiments, then we might be safe in assuming that
we had roughly comparable measures and could directly com-
pare the partial reward groups in the two experiments.

It will be recalled that, in the high effort experiment, the
criterion of extinction was six trials, not necessarily consecutive,
on which the animal did not reach the food compartment in 180
seconds. On the basis of some preliminary exploration, and on
the basis of hunch, intuition, and hope, we arbitrarily chose as
the criterion of extinction in the low effort experiment, six trials,
not necessarily consecutive, on which the animal did not reach
the food compartment in 30 seconds. We proved to be reason-
ably fortunate in this choice of criterion since we did obtain
rough comparability of measures for the 100 per cent reward
groups.

The effects of effort on resistance to extinction after partial
reward are shown in Table 7.3. This table presents the geo-
metric mean number of trials to extinction for the four low effort
groups and the comparable figures for the high effort experi-
ment. It may be seen from examining the first two rows of fig-
ures that we did, fortunately, achieve rough comparability of
measures of resistance to extinction. The two 100 per cent re-
ward conditions in the low effort experiment have averages of

146 EFFORT, EXPECTATION, AND REWABD

TABLE 7.3

AVERAGE TRIALS TO EXTINCTION FOR HIGH AND Low
EFFORT CONDITIONS (EXPERIMENT 15)

Effort

High. Low

100 Per Cent Reward 15.2 14.0

(zero trials) (N = ll) (N = 13)
100 Per Cent Reward 19.8 17.7

(54 trials) (N = 14) (N = 23)
Partial Reward 27 . 6 30.6

(16 unrewarded trials) (N = 37) (N = 23)
Partial Reward 52 . 4 38.2

(72 unrewarded trials) (N = 40) (N = ll)

14. and 17.7 trials to the criterion of extinction. The compar-
able figures for the corresponding high effort conditions are 15 . 2
and 19.8. The differences between the two experiments for the
100 per cent reward conditions are very slight.

The last two rows of figures in the table give the data for
the partial reward groups. It is clear that the difference between
the high and low effort groups that experienced 16 unrewarded
trials is negligible. The low effort group extinguishes in 30.6
trials and the high effort group in 27 . 6 trials. There is, however,
a large difference between the two effort experiments for the
animals that experienced 72 unrewarded trials. For both experi-
ments, as the number of unrewarded trials increases, there is a
marked increase in resistance to extinction. This increase is
large for the high effort condition and considerably smaller for
the low effort condition a difference significant at the . 02 level.
We thus have some tentative support for the statement that
additional physical effort, by increasing the magnitude of dis-
sonance that is introduced on unrewarded trials, augments the
effect of partial reward on resistance to extinction.

Although it is encouraging to have obtained such a differ-
ence between the high and low effort groups, one cannot ignore
the difficulty of interpreting all the data. If the greater exertion
of physical effort increases the magnitude of dissonance intro-
duced on each unrewarded trial, then one would expect the
effect to be discernible even after 16 unrewarded trials.

EFFORT, EXPECTATION, AND REWARD 147

The difficulty lies in the essential non-comparability of our
measures. In order to get some degree of comparability between
the two experiments, we tried to, and were successful in, obtain-
ing roughly equal resistance to extinction for the 100 per cent
reward conditions. And it is only with respect to this base line
that the two experiments show equal resistance to extinction
after 16 unrewarded trials. But if one had measures of resist-
ance to extinction that were really comparable, would we the-
oretically expect the 100 per cent reward conditions in the high
and low effort experiments to be equal?

As we pointed out early in the chapter, it is impossible to
answer this question generally. It depends on whether the extra
attractions which have developed in the high effort condition
are or are not sufficient to outweigh the greater deterrent effect
of high effort during extinction. Because of this unclarity we
really cannot directly compare the resistance to extinction of
separate groups between the high and low effort condition. One
is safe only in comparing the increment in resistance to extinc-
tion as the number of unrewarded trials increases. On this com-
parison, which is quite unambiguous, we have clear evidence
supporting our theory.

Nevertheless, even though the results are favorable, the me-
thodological problems left us somewhat unhappy, and we there-
fore performed an additional experiment in an attempt to obtain
a comparison that would be methodologically more adequate.

Experiment 16. Partial Reward with and without
Physical Efort

We attempted to solve the problem of comparability by an
extension of the placing experiment (Experiment 6) that we re-
ported in Chapter 4. It will be recalled that three groups were
run in that experiment: (1) a 100 per cent reward group; (2)
a 50 per cent reward group; and (3) a "placed" group, which
had the same reward schedule as the 50 per cent reward group
but was placed directly in the goal box on unrewarded trials.
We found that the "placed" group did not show any greater re-
sistance to extinction than did the 100 per cent group. Since this
"placed" group had exactly the same pattern of rewards and

148 EFFORT, EXPECTATION, AND REWARD

non-rewards as the 50 per cent reward group, it is possible to
view it as a condition demanding no effort on unrewarded trials.
This "placed" group also discriminated between trials when it
was placed in the goal box and not rewarded and trials when it
had to run the alley; on placed trials, therefore, these animals
had no expectation of any reward. Thus, the "placed" group
differed from the partially rewarded group both in lack of effort
and in lack of food expectation on unrewarded trials.

By adding a fourth group to such an experiment we could
have a more definitive test of both the effect of expectation and
the effect of physical effort. This fourth group would be a "par-
tial placed" one. It would be treated similarly to the "placed"
group: that is, every time the animals in the "partial placed"
condition ran the runway, they would be rewarded. On trials
that were unrewarded they would be placed directly in the goal
box. But these animals would also be given some trials on which
they were placed directly in the goal box and were rewarded.
They would in this way maintain an expectation of reward and
would look for food on those trials when they were placed di-
rectly in the goal box. There still would be a clear differential,
however, between this group and the normal 50 per cent reward
group in the amount of effort expended on unrewarded trials.
Thus, this "partial placed" group, when compared with a usual
partial reward group, would enable us to assess the effect of
increased effort on resistance to extinction following partial
reward. The comparison between the "partial placed" and
"placed" groups would show the effect of expectation on unre-
warded trials.

There is some evidence in the literature that such a partially
placed group is definitely superior to a placed group and even
somewhat superior to a group that is rewarded 100 per cent of
the time. Lewis and Cotton (1958) report a study in which,
after training on a black-white discrimination, all animals were
given a series of massed placements in the "correct goal box."
One group was rewarded on each placed trial, another group
was never rewarded on any of the placed trials, and a third
group was rewarded on 50 per cent of these trials. Following
this placement procedure, extinction trials were run. The ani-

EFFORT, EXPECTATION, AND REWARD 149

mals that had only unrewarded placements extinguished most
quickly. The animals that had a 50 per cent reward schedule
on the placements went back to the "correct goal box" signifi-
cantly more often during extinction than those that had only
rewarded placement trials. In other words, there is evidence
that a "partial placed" group will be more resistant to extinction
than either a "placed" group or a 100 per cent group. From these
data, however, we do not know how a "partial placed" group
would compare with a normal 50 per cent reward group. On
the basis of dissonance theory we should expect the normal 50
per cent group that expends more effort to be more resistant to
extinction.

The experiment that we ran was a replication of Experiment
6, with the addition of the "partial placed" group. This "partial
placed" group was run exactly as the "placed" group, with one
exception: on each day they were given an additional trial, ran-
domly inserted among the other trials. On this additional trial
they were placed directly in the food compartment, where they
found food. In other words, the 100 per cent reward group ran
the runway and found food six times a day; the 50 per cent re-
ward group ran the runway six times a day, finding food three
times in six trials; the "placed" group ran the runway three times
a day, finding food each time, and were placed in the food com-
partment three times each day with no food available; the "par-
tial placed" animals ran three trials each day, finding food on
each trial, and were placed directly in the food compartment
four times each day, finding food on one of these four placed
trials. The acquisition trials lasted for 12 days. Following this,
extinction trials were run (also six a day), all groups of animals
being treated identically. If, during extinction, an animal did
not reach the food compartment in 60 seconds, it was removed
from the apparatus.

Table 7.4 presents, for these four groups, the average num-
ber of trials to reach a criterion of extinction (two trials, not
necessarily consecutive, on which the animal failed to reach the
food compartment in 60 seconds). The three groups that con-
stituted a replication of Experiment 6 show confirming results.
The 100 per cent reward condition has an average of 18 . 3 trials

150 EFFORT, EXPECTATION, AND REWABD

TABLE 7.4

AVERAGE NUMBER OF TRIALS TO EXTINCTION
IN PLACING vs. RUNNING EXPERIMENT (EXPERIMENT 16)

Mean Number of
Training Condition N Trials to Extinction

100 Per Cent Reward 12 18 . 3

50 Per Cent Reward 12 38.3

"Partial Placed" 12 30.5

"Placed" 10 15.4

to extinction, the "placed" group again shows slightly faster ex-
tinction, with an average of 15.4 trials, and the 50 per cent re-
ward group is significantly ( .01 level) more resistant to extinc-
tion than either of them, taking an average of 38.3 trials to
reach the criterion.

The results for the "partial placed** group are of particular
interest. They take 30.5 trials, on the average, to reach the
extinction criterion. These "partial placed" animals are signifi-
cantly ( .01 level) more resistant to extinction than the 100 per
cent reward animals or the "placed'" animals. In other words,
if one creates a situation in which the animal expects to find
food, looks for it, and does not find it, one has introduced dis-
sonance and thus increased the resistance to extinction, even
though the amount of physical effort is very slight on these un-
rewarded trials. The "partial placed" animals, however, are sig-
nificantly less resistant to extinction ( . 05 level) than the 50 per
cent reward animals. This comparison, of course, gives a clear,
unambiguous picture of the effect of effort itself. If, holding
expectation constant, the amount of effort on the unrewarded
trials is increased, the magnitude of dissonance introduced on
these trials is greater, and the resistance to extinction is cor-
respondingly greater.

It is also of interest to look at the running times during ex-
tinction for these four groups of animals. All animals were run
for at least 30 trials, that is, for five days of extinction trials.
Figure 7.1 presents the average nrrming times by days of ex-
tinction for the first five days. It is clear that the differences we
observed on number of trials to an extinction criterion are also
present when we look at the running times. The running times

EFFOBT, EXPECTATION, AND BEWABD

151

40

c
o
o

30

QJ

O

2

2

z:

(T
bJ

20

10

o "Placed"
100 % reward
x "Partial placed"
o 50% reward

12345
DAYS OF EXTINCTION ( 6TRIALS PER DAY)

FIG. 7.1. RESISTANCE TO EXTINCTION AFTER PLACING AND PARTIAI-
REWARD (EXPERIMENT 15)

for the last days of acquisition are not presented because all
four groups were almost identical, averaging either 1.7 or 1.8
seconds.

The 100 per cent reward group and the * placed'* group are
very similar in their running times during extinction. The only
difference is a slight one on the second and third days, during
which the "placed" group was somewhat slower. The 50 per
cent reward group and the "partial placed" group are both con-
siderably faster during extinction than the other two groups. On
the third day of extinction the curves of running times for the
50 per cent reward animals and the "partially placed" animals
begin to diverge. The 50 per cent reward animals, which ex-
pended more effort on unrewarded trials, continue to run rather
fast, while the "partial placed" animals, which expended less
effort on unrewarded trials, begin slowing down very markedly
on the fourth and fifth days. We can accept the assertion that
increased effort during partial reward intensifies the effect of
unrewarded experiences on resistance to extinction. Since this

152 EFFORT, EXPECTATION, AND REWARD

relationship with effort is implied by the theory of dissonance,
these results should be taken in support of our interpretation.

Effort and Expectation

There are some interesting aspects to the results we have
just described which warrant further discussion. The data are
certainly clear in showing that increased physical effort intro-
duces more dissonance and results in increased resistance to ex-
tinction. The data are equally clear in showing that a very large
effect is obtained by simply creating, and disconfirniing, an ex-
pectation for food. After all, the average number of trials to a
criterion of extinction was only 18.3 trials for the 100 per cent
group as compared with 30.5 trials for the "partial placed"
group. In other words, even with a minimum of physical effort
required on the unrewarded trials, a situation where the animal
looks for food and does not find it results in a marked increase
in resistance to extinction. The fact that an additional effort
requirement on unrewarded trials makes resistance to extinction
even greater is, of course, of crucial theoretical interest to us,
but it does not detract from the importance of the effect of
simply not finding reward when the animal looks for it.

These data have important bearing on the explanations of
partial reward effects which have been proposed by theorists
such as Weinstock (1954) and Estes (1959). The fact that re-
sistance to extinction is so markedly enhanced by the mere dis-
confirmation of an expectation, even when the animal does not
perform the complete act of running the alley, presents a strong
argument against any theoretical account of partial reward
effects that relies on the concept of competing responses. These
explanations demand that the failure to find food when it is ex-
pected should give rise to competing responses. Even more im-
portantly, these competing responses should become anticipa-
tory so that they occur while the animal is running the alley.
In our "partial placed" group, however, this latter is very un-
likely to have taken place. The disconfirmation of the expec-
tancy never occurred on trials when the animal ran, only on
placed trials. Thus there is every reason for the animal to make
a distinction between the consequences to be expected on run-

EFFORT, EXPECTATION, AND REWARD 153

ning and on placed trials, and little reason for competing re-
sponses to occur on the former. That this is true in our experi-
ment is suggested by the fact that the running times of the
"partial placed" and 100 per cent reward animals were strictly
comparable throughout training. Granted, then, that such com-
peting responses did not become anticipatory for the "partial
placed'* animals, there is no way in which "competing response"
explanations could account for the increased resistance to ex-
tinction found for this group.

These data also lead us to some interesting implications con-
cerning the effect of magnitude of reward on resistance to ex-
tinction. By now, it is undoubtedly clear to the reader what the
theory of dissonance would have to say about variations in mag-
nitude of reward. One obviously must consider the amount of
reward in relation to the amount of effort required of the animal
in order to assess the magnitude of dissonance that would be
introduced on any given trial, even when the animal finds food
on every trial. Certainly, it would be possible to find a situation
where the effort required was high enough, and the amount of
reward was low enough, so that each trial introduced appreci-
able dissonance. Holding the effort requirement constant, the
smaller the amount of reward, the more dissonance would be
introduced and the greater would be the resistance to extinction.
One would therefore expect that with 100 per cent reward dur-
ing training, less reward should be associated with greater re-
sistance to extinction.

What, however, would we say about the effects of magnitude
of reward on animals trained on a partial reward schedule?
Under such circumstances, of course, the magnitude of disso-
nance introduced on unrewarded trials far outweighs the effects
of effort on rewarded trials. We have seen that expecting and
being oriented toward food is crucial on the unrewarded trials.
It seems plausible, consequently, to expect that the larger the
amount of food that the animal is accustomed to receiving as
a reward, the greater will be the dissonance introduced on an
unrewarded trial. Since a greater magnitude of dissonance will
result in greater dissonance reduction through developing some
extra attraction in the situation, we come to an interesting con-

154 EFFORT, EXPECTATION, AND REWABB

elusion: with partial reward training, greater magnitude of re-
ward should result in greater resistance to extinction.

An excellent experiment is reported in the literature which
is directly pertinent to the above discussion. Hulse (1958) re-
ports a study in which he varied percentage of reward and
amount of reward. Four conditions that he reports are of in-
terest to us: 100 per cent reward with 1.0 gram of food, 100
per cent reward with . 08 gram, 46 per cent reward with 1 .
gram, and 46 per cent reward with 0.08 gram. There are, in
other words, two conditions of 100 per cent reward, one receiv-
ing a relatively large amount of food and the other a very small
amount, and two comparable conditions of partial reward.

The animals were run in a straight runway to food. Each
animal was given only one trial a day. After preliminary train-
ing they were given 24 training trials. The partial reward groups
thus had 13 unrewarded experiences. They were then given 19
extinction trials, again only one a day. Table 7.5 presents the
mean running speeds for the four conditions mentioned above.
There were 18 animals in each group.

TABLE 7.5

MEAN RUNNING SPEEDS DURING EXTINCTION
FOR FOUR CONDITIONS FROM EXPERIMENT BY HULSE (1958)

Amount of Reward Reward Schedule

100% 46%*

1.0 gram 12.5 44.0

0.08 gram 21.3 25.0

The results are rather striking. When trained on a 100 per
cent reward schedule, the animals that received a very small
reward were significantly more resistant to extinction than those
that received a large reward. For animals trained on a partial
reward schedule the reverse is true: the large reward group is
significantly more resistant to extinction than the small reward
group. We have confirmation, then, of two points : ( 1 ) too small
a reward for 100 per cent animals may result in dissonance, and
(2) greater dissonance is introduced on an unrewarded trial if
the animal is accustomed to a large reward than if it is accus-
tomed to a small reward.

EFFORT, EXPECTATION, AND REWARD 155

Summary

We have presented and discussed experimental evidence re-
lated to three variables effort, expectation of reward, and mag-
nitude of reward. The following implications of our theory have
been supported:

1. Increased effort results in greater resistance to extinction re-
gardless of the reward schedule.

2. Even with minimal effort involved, the absence of reward
when the animal is oriented toward obtaining reward in-
creases its resistance to extinction.

3. The greater the magnitude of reward expected, the greater
the dissonance introduced on an unrewarded trial and the
greater the consonance on a rewarded trial. Thus, with 100
per cent reward, the larger reward decreases resistance to
extinction, whereas with partial reward it increases resist-
ance.

In addition, we have presented experimental evidence that
casts doubt on "competing response" explanations of the partial
reward effect.

8

A Speculative Summary

We have presented a new explanation for a considerable body
of empirical data. Specifically, we have applied the theory of
dissonance to explain why partial reward, delay of reward, and
effort expenditure during training result in increased resistance
to extinction. We have tried to demonstrate that this theoretical
explanation has validity. It can account for data with which
other theories have difficulty 3 it integrates empirical phenomena
that have been regarded as unrelated, and it is supported by the
results of experiments designed specifically to test its implica-
tions.

When a new theoretical explanation is offered, however, one
must look at it critically. Are there vaguenesses and ambiguities
in the theoretical statement; do data exist that are not compat-
ible with the theory; are there other more plausible and more
parsimonious explanations of the same data? By way of sum-
mary, we shall take a critical look at the theory and the data,
and, at the same time, indulge in -some speculations concerning
broader implications of the theory.

The bare skeleton of the theory, as applied here, can be sum-
marized briefly: If an organism continues to engage in an activ-
ity while possessing information that, considered alone, would
lead it to discontinue the activity, it will develop some extra
attraction for the activity or its consequences in order to give
itself additional justification for continuing to engage in the
behavior. In rather loose terms, this is the entire statement of
tfie theory. Clearly, in order to make any predictions from the

A SPECULATIVE SUMMARY 157

theory and to have them be relevant to data, some flesh has to
be put on this skeleton. Let us examine precisely how this is
done, the problems that arise, and the problems that remain
unsolved.

How do we know when an organism possesses information that,
considered alone, would lead it to discontinue an activity?

One must, of course, specify on independent, a priori grounds
when an organism can be said to possess information that is dis-
sonant with continuing an activity. By definition, if an organism
possessed only information dissonant with engaging in some
activity, we would observe a cessation of the activity. But we
are interested primarily in situations where the organism also
has consonant information so that it continues to engage in the
behavior in spite of the dissonance. In such a situation, how-
ever, one ought to be able to see some hesitation, some evidence
of unwillingness to perform the action. Such hesitation might
then be an indication of the existence of dissonance. Indeed,
in situations which intuitively fit our theoretical requirements,
such as partial reward and delay of reward situations, hesita-
tion and longer running times are observed during acquisition
trials.

There are difficulties, however, in relying on such a measure
as an indication of the existence of dissonance, the major one
being that this particular measure is obtained during the process
(according to the theory) of the development of extra attrac-
tions. Would not the development of these extra attractions, if
the theory is correct, interfere with the validity of such a meas-
ure as an indication of the existence of dissonance? The answer,
of course, is yes. There are many indications in data in the lit-
erature that as training progresses, the difference in running
speeds between, say, a partially rewarded group and a 100 per
cent rewarded group tends to become less and less and ulti-
mately to disappear; sometimes it even reverses its direction
(Goodrich, 1959).

The solution that we offer to this problem is to propose that
one test whether a variable produces such hesitation effects gen-
erally in a standardized test apparatus. One would have animals

158 A SPECULATIVE SUMMARY

run a simple runway for food. Any factor which, when intro-
duced, slowed their running, would be said to represent infor-
mation dissonant with running. We would of course find that
soon after the introduction of unrewarded trials, delay of re-
ward, or increased effort the running would be slower. We thus
accept this test procedure as an operational measure of whether
or not a given factor provides the animal with information dis-
sonant with continuing to engage in an activity. According to
the theory, any variable that produces hesitation in our test
apparatus will result in the development of extra attraction after
a reasonably prolonged series of trials, provided the animal does
not stop performing the action. It is necessary to point out that
this operational definition, although it sounds very precise and
specific, is not foolproof. There are things that could produce
hesitation in an animal that are not, we would all agree, deter-
rents to action. For example, the sudden introduction of some
new stimulus, like the sound of a buzzer, would undoubtedly
slow the animal down temporarily. How to distinguish such
factors from true deterrents without resorting to our intuition
is an unsolved problem. Perhaps the temporary nature of the
effects of the introduction of novel stimuli would provide a key
to making this distinction operationally.

Nonetheless, our operational specification enables the theory
to have some predictive power. It brings together, as psycho-
logically identical, various operations that appear to be differ-
ent. We have shown that partial reward, delay of reward, and
effort expenditure, all three of which are similar from the point
of view of dissonance theory, do indeed have similar effects in
prolonging resistance to extinction.

There is in the literature, however, a group of studies which,
at first sight, seems to contradict our theoretical interpretation.
At least one kind of situation has been studied in which partial
reward during training does not increase resistance to extinc-
tion, the crucial aspect of this situation being that the sequence
of rewards and non-rewards is patterned in certain special ways.
Thus it has been shown that if rewards and non-rewards alter-
nate, partial reward results in no greater resistance to extinction
than does 100 per cent reward (Tyler et at, 1953; Capaldi,

A SPECULATIVE SUMMARY 159

1958). It has also been shown (Grosslight and Radlow, 1956,
1957) that if all the unrewarded trials occur only at the end of
a day's runs, partial reward does not increase resistance to ex-
tinction.

This apparent contradiction with our theory can be dealt
with rather easily. If the patterning of rewards and non-rewards
is such that the animal can discriminate between trials that are
to be rewarded and those that are not to be rewarded, then par-
tial reward will not increase resistance to extinction. What hap-
pens, of course, is that the animal does not expect food on an
unrewarded trial and so such a patterning fails to produce any
dissonance. That is, when the animal does not expect food, not
finding food does not introduce dissonance. As one might ex-
pect, when rewarded and unrewarded trials are alternated, run-
ning times on unrewarded trials are much longer than on re-
warded trials. In short, if the animal does not expect food, it
shows little eagerness to run and no dissonance is introduced.

The same kind of discrimination between rewarded and un-
rewarded trials undoubtedly occurs in the experiments in which
unrewarded trials conclude the day's runs. As the animal gets
close to the last trials of the day, it may stop expecting rewards
and the unrewarded trial then may have a different significance.
We hesitate to emphasize this explanation, however, because
the studies that have been reported suffer from other difficulties
also. They deal with discrimination and reversal learning under
conditions where the initial discrimination is very inadequately
learned. Inadequate learning may also have interfering effects.

There does exist one study that we are unable to explain to
our own satisfaction. Wike et al (1959) report a study using
patterning of delay of reward and immediate reward. From our
theory, we would not expect patterning to affect delay of reward
in the same way that it affects partial reward. Even if the ani-
mal expects the delay, it should still introduce dissonance-in-
deed, if it did not, how would one account for the increased
resistance to extinction resulting from delay on every acquisi-
tion trial?

This experiment by Wike et al contains two parts. In one
part a random mixture of delayed and immediate rewards is

160 A SPECULATIVE SUMMAHY

compared with an alternating sequence. As we should expect
with delay of reward, the animals that experienced the alternat-
ing sequence are as resistant to extinction as the other group.
In the other part of the study, the authors compare a group re-
ceiving no delays, a group receiving delay in the middle of a
day's runs, and a group receiving delay at the end of a day's
runs. We should, of course, expect both of the delay groups to
be equally superior to the group that was always rewarded
immediately. But this is not the case. On the contrary, the
group that received delay only at the end of the day's runs was
less resistant to extinction than the other delay group and about
equal to the immediate reward group. This result is surprising
to us and we have no ready explanation for it. Should it prove
to be a replicable finding, it would mean that factors other than
the ones with which we have dealt must also be taken into con-
sideration.

All in all, the data on partial reward, delay of reward, and
effort fit our theory well But have we examined in detail other
factors that also fit our operational definition? The answer is
clearly no. There is at least one major gap in the data we have
presented, namely, data? on punishment. But these data should
certainly not be ignored. If we inserted punishment of some
kind into our test apparatus, it would certainly produce hesi-
tation. We should expect, then, that punishment would also
produce greater resistance to extinction in an appropriate situ-
ation. What do the data on punishment show?

At first glance, the series of studies done by Maier and his
students (Maier, 1949) on fixation of response following punish-
ment in an insoluble discrimination problem seem to confirm
our theory. Most of these studies have used a jumping stand
with two windows to choose between. The "correct window"
is varied randomly so that learning cannot occur. The "incor-
rect window'* is always locked so that, if the animal jumps to it,
it bumps its nose and falls down. The result of this procedure
is that an appreciable number of animals become "fixated'* on
one window and do not learn even when the problem becomes
solvable. Superficially, and loosely, these results would seem
to be compatible with dissonance theory. Perhaps the fixation

A SPECULATIVE SUMMARY 161

occurs because of some very strong extra attraction that has de-
veloped. On closer investigation, however, any such interpre-
tation proves to be most implausible, bordering on nonsense.
One finds that the reaction of the animals to the punishment is
really to discontinue the activity. They refuse to jump. In order
to make them jump one must give them considerable punish-
ment on the jumping stand itself, thereby forcing them to jump
in order to escape punishment. Certainly, it is unclear what dis-
sonance theory would or could predict when such a procedure
is used.

One study, by Klee ( 1944), attempted to dispense with pun-
ishment on the jumping stand. Klee fed his rats only when they
jumped to the correct window. They were not fed at all in their
cages. If a rat refused to jump, Klee left it on the jumping stand
for several hours before returning it to its cage. Such an animal
then had nothing to eat until the next day, when it again had
an opportunity to jump. Presumably, such an experiment should
have been decisive. Unfortunately, the number of rats that
starved to death rather than jump is extremely large. In other
words, this whole series of experiments does not fit our theoreti-
cal conditions. The animals do not continue to engage in an
activity while having information that would lead them to dis-
continue it. On the contrary, they refuse to engage in the ac-
tivity. Most of the experiments on punishment suffer from the
same kind of difficulties from our point of view. The animals
almost always have to be forced to engage in the activity which
is punished.

Logan (1960, p. 220), however, reports an experiment that
seems to avoid this difficulty and finds results that are intriguing.
He ran three groups of rats in a straight runway to food. One
group experienced shock in the runway on each trial, another
experienced the shock on 50 per cent of its trials, and the third
group never experienced any shock. During acquisition, the
"No Shock Group" ran fastest, as might be expected; the "Par-
tial Shock Group" ran next fastest; and the "100 Per Cent Shock
Group," by the end of acquisition, showed serious deterioration
of performance. This last group, in essence, showed signs of dis-
continuing the activity.

162 A SPECULATIVE SUMMARY

Extinction trials were ran with neither food nor shock. The
data on how resistant these animals were to extinction are of
interest to us here, particularly for the "No Shock Group" and
the "Partial Shock Group/* both of which continued to engage
in the activity. The "No Shock Group" extinguishes quite rap-
idly. The "Partial Shock Group/' however, continues to run
relatively fast. The average speeds for the two groups cross very
early in extinction, and the "Partial Shock Group" continues
thereafter to run faster than the "No Shock Group/' Logan offers
no explanation of these results. They are, however, clearly con-
sistent with what one would expect from dissonance theory.
Such results are encouraging, but in view of the possible com-
plex effects of shock, it would be desirable to have additional
confirmatory evidence.

Another interesting question that arises from our operational
definition of dissonance-producing variables concerns the dis-
tinction between incentives and deterrents. If we increased the
amount of effort involved in our test apparatus, we would ob-
serve slower running, and we would conclude that effort is a
deterrent to action and that information concerning effort is
dissonant with continuing the activity. If, however, we de-
creased the amount of food an animal obtains, we would also
observe slower running. We would not want to conclude that
a small amount of food is a deterrent or that the knowledge that
food is obtained is dissonant with continuing to engage in the
activity, for we know that food is an incentive. Consequently
there seems to be a problem with our operational measure.
Clearly, however, this is not a difficult operational problem,
since one distinction may easily be applied in the situation. If
one increases the magnitude of some variable and observes hesi-
tation of behavior, one may conclude that the variable is a de-
terrent. If one decreases the magnitude of the variable and
then observes slower behavior, one may conclude that it is an
incentive.

According to the analysis one would make from dissonance
theory, this distinction between deterrents and incentives is
rather crucial. We should not want to say that any magnitude
of incentive, however small, introduces dissonance with con-

A SPECULATIVE SUMMARY 163

tinuing to engage in the activity. There are data in the litera-
ture (Armus, 1959), however, showing that after training with
100 per cent reward, rats that obtained a large amount of food
extinguished more quickly than rats that obtained a small
amount. In other words, decreasing the amount of reward has
exactly the same effects in our test apparatus and in extinctipn
as increasing the delay of reward, effort, or any deterrent. Thus,
from these data it might appear that the distinction between
deterrent and incentive is not an essential one.

However, if we look at the theory and the data closely, the
distinction between incentive and deterrent remains a crucial
distinction. Let us recall the kinds of results that were obtained
with variables that were clearly deterrents. The effort variable
is a good example of this. As effort during acquisition was
increased, resistance to extinction increased. This was true
whether one was dealing with 100 per cent reward situations or
with partial reward situations. This uniformity of effect, how-
ever, was not found in connection with an incentive such as
magnitude of reward. It will be remembered from our discus-
sion in Chapter 7 that Hulse ( 1958 ) reports that smaller magni-
tude of reward leads to greater resistance to extinction after 100
per cent reward, but leads to less resistance to extinction after
partial reward. Clearly, incentives and deterrents do not pro-
duce the same results and must be distinguished operationally
and conceptually. The conceptual distinction between incen-
tives and deterrents which is made in our theory enabled us to
explain this pattern of results.

What variables affect the magnitude of dissonance and what
variables affect how much extra attraction will develop?

The skeletal theoretical statement presented at the begin-
ning of this chapter made no mention of the variables that de-
termine the magnitude of the effects involved. Clearly, for the
theory to be useful, there must be some specification of condi-
tions affecting the magnitude of dissonance and conditions af-
fecting the degree of extra attraction that develops. How have
these variables been specified in the theory, and to what extent
have the data supported the theory in these respects?

164 A SPECULATIVE SUMMARY

It was stated in Chapter 2 that as the magnitude of disso-
nance increases, the greater will be the attempts to reduce the
dissonance and, hence, the greater will be the development of
extra attractions in the situation. This statement, however, does
not solve any operational problems. We still must identify the
variables which affect the magnitude of dissonance. The theo-
retical exposition in Chapter 2 also states that as the magnitude
of a deterrent increases, the magnitude of the dissonance cre-
ated by continuing to engage in the action also increases. This
statement, of course, enables us to look at the data to see what
corroboration is offered.

In connection with partial reward, it is by no means imme-
diately obvious what one means by the magnitude of the deter-
rent. One's first thought might be that the magnitude of the
deterrent is to be interpreted as meaning the relative frequency
of unrewarded trials. But we have clearly demonstrated that
this is not the case. The resistance to extinction seems to be a
function only of the number of instances of unrewarded trials,
not of their relative frequency (Experiment 5, Chapter 4) . In-
deed, we were led to do Experiment 5 because it seemed likely
that the magnitude of dissonance experienced on any trial would
be determined by the things that happened on that specific trial.
Further, if this suggestion is correct, it seems plausible to specify
that the magnitude of the deterrent depends on how much re-
ward is expected on unrewarded trials. The point in mentioning
this again is to show some of the relative vagueness that exists
in parts of our theoretical statement. It is not always clear what
operations correspond to the theoretical requirements.

On the other hand, the specific operational manipulations
that increase the magnitude of dissonance are reasonably clear
in connection with other variables. For delay of reward, the
theory would imply that the longer the delay, the greater the
magnitude of the deterrent, and the stronger should be the ef-
fect. Whatever data exist in the literature tend to give some
support to this, but the data are scanty. We ourselves have not
investigated it at alL We have, however, devoted considerable
attention to the variable of effort. Here again, we should expect
that the greater the effort expended, the greater would be the

A SPECULATIVE SUMMARY 165

dissonance created. In general, our findings have supported
this. When greater effort is required during acquisition, regard-
less of whether the reward is partial or 100 per cent, the organ-
ism is more resistant to extinction.

We have said relatively little about the process by means o
which the animal develops some extra attractions in a situation
in order to reduce dissonance. Nor have we said much about
variables which would affect the rapidity and effectiveness with
which such dissonance reduction is accomplished. In the human
being there are a whole variety of dissonance reduction mecha-
nisms which seem to be effective, but this is probably not true
in a non-verbal organism like the rat. We have therefore tried
to specify a dissonance reduction mechanism that would seem
reasonable in a non-verbal organism. We assumed that, when
dissonance exists, the animal is able to discover things in the
situation, or in the activity, that satisfy its other subordinate
motives. If this suggestion is correct, then a number of inter-
esting questions may be raised.

Presumably, if the animal is able to find things that satisfy
subordinate motives, these motives must exist within the animal
rather constantly. If the animal is dominated by some strong
need such as hunger, these subordinate motives may remain
latent and not affect the animal's behavior. When dissonance
exists, however, these other motives may become more salient.
Still, it would seem plausible to argue that as long as an organism
is dominated by some strong drive, it is unlikely that these other
motives would affect behavior strongly. Such reasoning leads
one to the speculation that, if an animal experienced strong dis-
sonance under conditions of general weak motivation, disso-
nance reduction might be more effective and more pronounced
behavioral consequences would be observed. These considera-
tions led us to do the experiments reported in Chapter 6 using
minimal motivation during extinction. These experiments did
show that the effects of dissonance reduction were observable
under minimal motivation conditions, but we produced little
evidence to support the notion that these effects are stronger
under low than under high motivation.

It is perplexing that so little work has been done on rats

166 A SPECULATIVE SUMMABY

under conditions of weak motivation. When psychological re-
search is done on humans, it Is almost always under conditions
of weak motivation, but on animals almost always the opposite.
It is interesting to speculate that this may be one of the reasons
for the great difficulty of integrating research on animals with
research on humans. Behavior may be very different when a
single strong drive does not dominate. Harlow, Harlow, and
Meyer ( 1950 ) report some interesting data related to this. Mon-
keys show an intrinsic interest in certain kinds of puzzles and
will work on them for long periods of time. If, however, they
are given the experience of getting food by solving these puzzles,
their performance deteriorates. Certainly, more study of be-
havior under weak motivation is needed.

One other interesting point may be raised on the basis of
our hunch about the process of dissonance reduction in the rat:
if the rat reduces dissonance by finding elements in the situation
that satisfy other existing motives, then the characteristics of
the situation in which it finds itself will be an important deter-
minant of how effectively it can reduce dissonance. Psycholo-
gists who work with rats are in the habit of using extremely
barren situations for their experiments. There are, of course,
reasons for this the more barren the experimental apparatus,
the easier it is to control relevant variables. But if our specula-
tions are correct, a very barren experimental situation limits the
possibility of the organism to reduce dissonance. Perhaps if the
experimental environments were richer, more like the environ-
ments to be found in the natural habitat of the organism, the
effects one would observe would be stronger. Surely, the natural
habitat of an animal must possess many aspects capable of satis-
fying a wide variety of subordinate motives. We should like to
stress, however, that this particular mechanism for reducing
dissonance is not the only one available, nor is it probably avail-
able to all organisms. Higher organisms undoubtedly have ad-
ditional techniques for dissonance reduction. Humans certainly
have, and we would speculate that the higher the phylogenetic
development of the animal, the greater the variety and effective-
ness of its dissonance-reducing mechanisms. Certainly, disso-
nance reduction effects that can be shown only with difficulty in

A SPECULATIVE SUMMARY 167

the rat can be shown easily in the human. We would anticipate
that in a monkey, for example, intermediate magnitudes of ef-
fects would be found. And, as we pointed out in Chapter 2,
lower organisms such as fish are probably very ineffective at
dissonance reduction. Indeed, in fish, partial reward does not
increase resistance to extinction.

How can we measure the amount of extra attraction that an or-
ganism has developed as a result of dissonance reduction?

In order to test our theoretical statement, we must have some
way of measuring, behaviorally, whether or not, and the extent
to which, any extra attraction has developed in a situation. We
have, of course, dealt with this problem extensively, particularly
in Chapter 3. But a fresh look at how we have dealt with this
problem indicates that the solutions we have reached are not
very adequate. We reached the conclusion that resistance to
extinction was the best available indication of the existence of
extra attraction. It may be that it is the best available measure
in the sense that it is the only one that gives consistent results
in the theoretically expected directions, but it must be admitted
that it remains very indirect. Presumably, if extra attraction
has been developed in a situation, this should act as an incentive
for the animal. It seems odd, and certainly a bit indirect, to
measure the value of an incentive by observing how rapidly an
animal stops going to the place toward which it is supposed to
be attracted.

If one could demonstrate that, in the absence of any extrinsic
reward, an animal will learn a new action in order to get some-
where, this would be more direct and more convincing evidence
of some intrinsic incentive in the situation. Let us remember at
this point, however, that we have data showing our inability to
demonstrate a differential in new learning between a group that
theoretically had developed extra attractions and a group that
had not. In two experiments, both reported in Chapter 6, we
compared such groups of animals in a new learning situation.
In one experiment (Experiment 12) they had to learn to press
a bar in order to get into the box where extra attractions had
presumably developed. In the other experiment (Experiment

168 A SPECULATIVE SUMMARY

13) they had to ran a four-unit T-maze. In neither experiment
were any differences found between the two groups of animals.
Peculiarly, it was not that neither group learned the new task.
Both of them learned it rather rapidly a peculiarity we do not
understand. The important thing is that we obtained no differ-
ence between those that had presumably developed extra at-
tractions and those that had not.

What are the implications of our failure to demonstrate a
differential in learning a new task, and how can we explain this
failure? It is easy to say something like "the more one changes
the total situation from the original one, the less does one ob-
serve the effects of the extra attraction." But such a statement
does not explain anything. It is also easy to say that the extra
attraction is probably rather weak and hence does not show it-
self when the task is too difficult. But this is more an excuse than
an explanation. Even if the extra attraction is weak, why should
it not show itself, at least weakly? On the other hand, we do see
the effects of these extra attractions in extinction. Here they
seem reasonably stable. Indeed, when extinction trials were run
under very low motivation conditions, thus reducing competing
motives, there was little evidence of any true extinction process
(Experiments 9, 10, and 11). One is almost forced to conclude
that a new test situation produces stimuli and behavior (perhaps
exploratory) that result in a diminution of the strength of the
extra attractions. We have, however, devoted little attention to
discussing and analyzing the conditions under which extra at-
traction will decrease. The only thing we have said is that,
if there are competing incentives that cause the animal to decide
not to go to the place in which it has developed extra attractions,
this decision will cause a reversal of the process and the extra
attraction will begin to break down. This may be pertinent to
the new learning task if a wholly new situation evokes such com-
peting motives. Unless there are such refusals, explicit or im-
plicit, to go to the place that possesses extra attractions, we
would not expect them to have weakened, since there is no plaus-
ible reason to assume that simple disuse would cause the extra
attractions to disappear. All of this reasoning is rather ad hoc,
but unfortunately we have no better solutions to offer.

A SPECULATIVE SUMMARY 169

It would be unfair to end this chapter, and the book, with
only a summary of the difficulties and ambiguities that exist in
the theory and the data we have presented. Many things are
clear, a number of previously unexplained facts are adequately
covered by our theory, and, what is more, we have uncovered
several new phenomena. Perhaps the best summary we can
make of the positive contribution that this volume represents
is to list these new findings:

1. Resistance to extinction after partial reward is not a function
of the ratio of rewarded to unrewarded trials during acquisi-
tion. It is a function of the total number of unrewarded
trials.

2. If an animal is never rewarded in a given place but only de-
layed there, it will continue to run to that place during ex-
tinction longer than will animals that have either always
been rewarded in that place or have been partially rewarded
there.

3. If, before extinction trials are run, the animals are taken off
their deprivation schedule so that they are no longer hungry,
the same or even greater differences in resistance to extinc-
tion are obtained than would be the case if the animals were
hungry during extinction.

4. Partial reward effects are obtained even though the absence
of reward which disconfirms an expectation is never asso-
ciated with the response measured during extinction.

5. Increasing the effort that an animal must expend in order to
reach a reward increases the resistance to extinction.

It seems to us that these findings, together with the other
results that we have discussed in the book, are very difficult to
explain by any of the other existing theories. We saw in Chap-
ter 2 that the attempts at explaining partial reward effects by
Sheffield (1949) and Weinstock (1954) could not adequately
account for the experimental evidence. We saw, in addition, in
Chapter 4, that the expectancy idea, as proposed by Humphreys
(1939), or any form of discrimination hypothesis is also inade-
quate. We saw in Chapter 5 that the frustration hypothesis, as
proposed by Amsel (1958), cannot be applied to explain our

170 A SPECULATIVE SUMMARY

data concerning the effects of zero reward. Furthermore, as we
have pointed out, none of the previously proposed theories has
integrated partial reward, delay of reward, and effort expendi-
ture.

Our own explanation, of course, is neither perfect nor fully
developed. Nonetheless, it provides a basis for explaining many
puzzling experimental results and for integrating a variety of
variables. Its strength stems largely from the fact that it inverts
the traditional way of looking at such factors as non-reward,
delay of reward, and effort, all of which have historically been
viewed as inhibitors of behavior. Though not denying this as-
pect of their influence, we have regarded them as having, in
addition, a f acilitative effect. They indirectly create attractions
or incentives in the situation. They do this by creating disso-
nance in the animal and thus leading it to discover additional
satisfactions. It perhaps needs to be emphasized that these ad-
ditional satisfactions, or extra attractions, are developed through
a process quite different from secondary reward. Indeed, it is
almost opposite to secondary reward in that lack of rewards
leads to their development. On the other hand, both the disso-
nance reduction process and secondary reward may be seen as
means of developing "secondary reinforcers." This term is, of
course, purely descriptive, indicating simply that past experi-
ence of an unspecified nature has made a previously neutral set
of stimuli into potential "reinforcers" of behavior. The use of
this term, however, helps us to fit our own contribution into the
general context of learning and learning theory. What we have
proposed is a new mechanism by means of which "secondary
reinforcers" sometimes develop.

The specific process of dissonance reduction does, however,
invert many of the customary ways of looking at and explaining
learning and extinction. We are aware that this inversion of
the usual modes of explanation may not find easy acceptance,
but the fact that it leads to the clarification of a considerable
number of problems gives us hope for its future.

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Index

Index

Accumulation of extra attractions, 50-

51

Adaptation to frustration, 83, 119-20
Adelman, H. M., 11
Aiken, E. G., 10, 11
Alternation of reward and non-reward,

158-59

Amsel,A.,20,29,82,169
Amsel hypothesis, 26-28, 103, 113-15
Anderson, E. E., 137
Anticipatory frustration response, 27

28,82

Anticipatory goal reactions, 25-26
Applezweig, M. H., 40
Armus, H. L., 163
Aronson, E., 35, 61
Attraction and resistance to extinction,

61

Attractions, natural, 104
Attractiveness of goal box, 71ff

Bitterman, M. E., 16, 50, 105ff
Brightness preference, 72-73
Brunswik, E., 31

Capaldi, E. J., 158
Chance level of performance, 137
Choice behavior, 61, 67ff
Comparability of effort conditions,
144-45, 147

Competing response hypothesis, 20ff
Competing responses, 152-53, 155
Consonance, 43-44
Contrast between acquisition and ex-

tinction, 14-16, 29, 56, 94, 96, 98,

113
Contrast between zero and 100 per

cent reward, 104-5
Cotton, J. W., 85, 148
Cumulative effects of dissonance re-
, duction, 48-50, 85ff, 87ff, 144flE

D'Amato, M. R., 67, 69
Delay of reward, 5, 8-10, 16, 25-26,
30-32, 40ff

patterning effects in, 159-60

percentage of, 9, 102

zero reward and, 107, 113
Denny, M. R., 11
Deterrents to action, 39-41, 164

distinguished from incentives, 162-
63

operational definition of, 158
Discrimination hypothesis, 5, 14-17,

85, 94, 169
Dissonance, 33ff

behavior changes, 34

definition of, 36

hesitation and, 53, 157-58

importance and, 42

magnitude of, 40-41, 44-45, 163-65

motivational aspects, 34

non-verbal organisms, in, 35, 165

operational definition of, 157 ~/
Dissonance-producing trials, 84-85
Dissonance reduction, 34, 44fE

acquisition and, 53-55

behavior change and, 45

178

INDEX

cumulative aspects of, 48ff

effectiveness of, 165ff

environment and, 166

limits of, 50ff

mechanisms for, 46, 47-48

motivation and, 116J0E

rate of, 49-51

resistance to extinction and, 55-58

Elam, C. B., 106

Effort, 5-6, 10-12, 30-32, 40, 139ff

absence of, 148-49

behavior change and, 40

comparability of measures, 144-45,
147

extinction and, 140ff, 147-50

interaction with expectation, 152ff

manipulation of, 88

methodological problems, 144-45

partial reward and, 143ff, 147ff

variability in, 140-42
Estes, W. K., 21ff, 152
Expectancy, 41, 88, 99, 148, 150, 152ff,

164, 169
Expectation of non-reward, 99ff, 147,

159
Expectation of reward, 68-69, 101-2,

164

Externalized motivation, 137
Extinction, resistance to, 3-4, 55ff, 70ff

after non-response acquisition, 99ff

beginning of, 95-97

failure of, 121, 125-27

indirect measure of attraction, 71

intrinsic attraction and, 71ff

magnitude of reward and, 153-54,
163

number of acquisition trials and, 86- '
87, 90ff

overlearning and, 92

miming speed during, 111-12, 124,
126-27, 132-33

sensitivity of measurement, 71

strength of motivation and, 121ff

time in goal box and, 86

zero reward and, 108-9
Extra attractions, 34, 47ff

associated with activity, 62-63, 77,
81

associated with place, 67, 70-71, 77,

81, 128-29, 133
cumulation of, 69
decrement in, 52, 69, 168
development of, 128
dissonance arousal and, 84
dominant motivation and, 117ff
durability of, 52, 57
exploratory behavior and, 168
extinction test for, 70ff
locus of, 47-48
measurement of, 167-68
new learning test for, 61ff, 133ff
preference test for, 67ff, 128-29, 131
secondary reward and, 104
summation with extrinsic reward,

63ff

Feddersen, W. E., 105
^Fehrer, E., 10
Festinger, L., 33
Fixation of response, 160-61
Free choice tests, 31ff, 68-70
Frustration drive, 27-29, 113-15
Frustration hypothesis, 103, 169
Frustration reactions, 27-29, 103, 119

adaptation of, 83, 119

anticipatory responses, 82

Generalization of partial reward effects,

81

Goodrich, K. P., 157
Gradient of reward, 5
Grosslight, J. H., 159

Harlow, H. F., 166
Harlow, M. K., 166
- HuU, C. L., 2
Hulse, S. H., Jr., 154, 163
Humphreys, L. G., 6, 169
Humphreys hypothesis, 14-16, 85, 88

Incentive motivation, 25

Incentives, 116

Information items, 33-40, 42-43, 52,

116
Intertrial vs. intratrial effects, 22-24,

29
Intrinsic interest, 166

INDEX

179

Jenkins, W. O., 7
Justification of behavior, 33

Kate, S., 22, 23
Kimble, G. A., 122
Kivy, P., 67, 69
Klee, J. B., 161
Klein, R. M., 70

Lachman, R., 67, 69

Latency of response, 3

Latent extinction, 122, 125, 130, 134,

136

Lewis, D. J, 7, 19-20, 85, 148
Logan, F. A., 4, 25, 29, 31, 40, 161
Logan hypothesis, 25-26, 28
Longo, N., 50

Maatsch, J. L., 11

McNamara, H. J., 9, 16, 26, 102

Maier, N. R. F., 160

Marx, M. H., 105, 106

Mason, D. J., 68, 173

Meyer, D. R., 166

Miller, N. E., 135

Mills, J., 35

Motivation, 44ff

dissonance and, 44

dominant, 47, 51, 116-17

extra attraction and, 117ff

partial reward and, 116-19

salience of, 164

speed of running and, 119, 120-21,
123 132

subordinate, 47ff, 117, 127-28, 165

weak, 117, 120-21, 165-66
Mowrer, O. H., 16, 26
Myers, A. K., 135
Myers, J. L., 62

Non-response acquisition, 146-47

partial reward and, 148ff
Novel stimuli, 158

Operant level of running, 124

Partial punishment, 161-62
Partial reward, 6-7, 30
adaptation to, 70

explanations of, 13ff

generalized effects of, 81

in fish, 50

magnitude of reward and, 153-54

patterning of, 159

percentage of, 7-8, 85, 89ff, 94-95
Performance stabilization, 54
Performance variability, 127
Phylogenetic differences, 49-50, 166-

67
Preferences, 72

choice test for, 128-31

natural, 72-74

resistance to extinction and, 32

running speed and, 73-74

weak, 82

Procter, D. M., 135
Psychological implication, 37

operational measurement of, 38ff
Punishment, 160-62

Radlow, R., 159
Refusal to run, 56-58
Reinforcement, 4-5
Response amplitude, 4
Response frequency, 2-3
Response strength, 2-9
Reward, 5, 105

magnitude of, 43

variation in per cent of, 8992
Running speed during acquisition, 79-

80, 96-97, 111, 122-26, 157-58
Runway vs. goal box effects, 75ff, 78ff

Saltzman, I. J., 70

Secondary rewards, 61-62, 64, 66, 70-
71, 135

Seward, J. P., 135

Sheffield, V. F., 17, 25, 29, 169

Sheffield hypothesis, 17-20

Spaced vs. massed trials, 19-20

Spence, K. W., 27

Stanley, J. C., 7

Stimulus aftereffects, 17-19
" Stimulus generalization, 24
' Stimulus generalization decrement, 18

Stimulus traces, 19

Theios, J., 98

180 INDEX

Thompson, M. E., 32 Weak motivation, 64-66

Tyler, D. W., 105, 106, 158 Weinstock, M. G., 86

Weinstock, S., 7, 8, 21, 25, 82, 152, 169

Uncertainty of information, 54 Weiss, E. J., 20

Urnnotivated learning, 135-37 Weiss, R. F., 11

Unrewarded trials, 40-41, 54 Wike, E. L., 9, 16, 26, 102, 159

cumulative effect of, 86ff Willingness to perform, 53

number of, 85ff, 143ff, 164 Wilson, W., 20

patterning of, 158-59 Wodinsky, J., 50

Wagner, A. R., 114-15 Zero reward, 103ff, 107ff 121ff

Weak differential attraction, 73-74, 82 x 'Zimmerman, D. W., 62, 63, 67

Winner of the, 1959 Socio-Psychological

Prize of the American Association for
the Advancement of Science

The Psychology of Affiliation

Experimental Studies of the Sources of
Gregariousness

STANLEY SCHACHTER

"In terms of a solid contribution to

psychological science there can be no
doubt that this study of the ailiative

needs of man and their relationship to
anxiety and to biological and social needs
J|1 lj ttle short of being a minor classic,
-IK' worthwhile is the investiga-
te ui udinal position in the family,"-
Social Order

"Every now and then in social psy-
chology experiments are performed that
do speak to the scientist, A discovery of
this import seenis to have emerged from
the work of Stanley Schachter and his
colleagues, . , , The discovery is sig-
nificant, The work is careful, and the
presentation is lucid, , , . An excellent
model for experimental social scientists,
, . . A solid contribution to social psy-
chology "-Contemporary Psychology

Stanford Studies in Psychology, I. $3,75