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Dictionary of the History of Ideas

Studies of Selected Pivotal Ideas
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It is sometimes said that La Mettrie, or Hobbes, or
even Aristotle was the first behaviorist. But such claims
ignore the cardinal point that behaviorism was essen-
tially a methodological movement in psychology which
can only be understood in the historical context of the
early twentieth century. Its basic tenet, proclaimed by
John B. Watson, its founder, was that psychology could
only become a science if it based itself on the sort of
objective observations and measurements that were
made by natural scientists and biologists. This claim
had point because it was made at a time when intro-
spective psychology had run itself into the ground with
abortive controversies about imageless thoughts and
when, by contrast, the study of animal behavior, which
had received great impetus from Darwin's theories, was
advancing rapidly. The time, therefore, was ripe for
Watson's polemical suggestion that the only way to
advance the scientific study of human beings was to
adopt the same sorts of observational techniques that
had proved so successful with the study of animals.
This was the kernel of behaviorism and, incidentally,
about the only doctrine which was common to all those
who later called themselves behaviorists.

Connected with this claim about the appropriate
data of science was a view about the proper function
of science. Watson held that the function of science
was not so much to explain events but to predict and
control them. Behaviorism therefore had close affinities
with certain aspects of American pragmatism as repre-
sented by John Dewey, Charles Peirce, William James,
and fitted in well with the general American tendency
to believe that the obvious way to improve the condi-
tion of man was to manipulate the external environ-
ment which was regarded as the main determining
influence on his behavior.

What, then, has led people to claim that previous
figures in the history of psychology, such as Hobbes
and Aristotle, might be termed behaviorists? Partly,
perhaps, the fact that many others before Watson had
approached the study of man objectively, but without,
in fact, relying much on introspective reports; for there
were previous thinkers who had proceeded more or
less in this way without erecting it into a methodologi-
cal doctrine. More important, however, was the fact
that there were other doctrines espoused by Watson
which fitted well with his methodological directives,
and previous thinkers had advanced these doctrines.

Watson, like many other behaviorists, held a tacit
or an implicit metaphysical doctrine about the sort of
entities that there are in the world. He was a materialist
who believed, for instance, that thought was identical
with movements in the brain and larynx. Connected
with his materialism was his view about the sort of
concepts that were appropriate in developing a science
of psychology. Like Hobbes before him and Hull after
him he believed that the concepts should be mechani-
in character. This belief was shared by many later
conceptual behaviorists who were not prepared to take
up any position on metaphysical issues which, they
claimed, lay outside the province of science. Finally
Watson was an associationist in his theory. He believed
that simple reflex arcs were linked together in behavior
by principles of association. In this respect his theory


was quite unoriginal: for he merely transferred to the
sphere of simple bodily movements a theory which had
previously been put forward to account for the links
between simple ideas. He stressed the importance of
peripheral connections between stimuli and minimized
the role of central processes. He thus founded what
has come to be called the S-R (Stimulus-Response)
theory of learning.

When, therefore, assertions are made about the more
remote historical origins of behaviorism these usually
relate not so much to the methodological doctrine,
which was central to it as a movement in psychology,
as to other aspects of Watson's thought, which not all
behaviorists shared—to his materialism and to his use
of mechanical concepts and of associationist principles.
There was also the less self-conscious use of objective
methods by many before who studied human behavior.

This brief analysis of what was distinctive of behav-
iorism suggests a convenient method of treating it as
a phenomenon in the history of ideas. A few key figures
in the history of psychology will first be introduced
to substantiate the position here defended that only
in rather contingent respects could they be regarded
as precursors of behaviorism. This will pave the way
for the exposition of the more closely connected ante-
cedents of behaviorism as a movement in the history
of psychology.


1. Aristotle. Many things in the history of thought
have been traced back to Aristotle with varying de-
grees of appositeness, but there is almost nothing ap-
posite in tracing back behaviorism to him. To credit
him, for instance, with taking up a position on the
central methodological issue of the use of publicly
observable data, as distinct from introspective evi-
dence, in studying human beings would display a gross
lack of historical perspective; for the distinction be-
tween the private world of the individual's own con-
sciousness and the public world, which all could ob-
serve, was alien to the Greeks. Indeed there is a sense
in which the Greeks had no concept of consciousness
in that they did not link together phenomena such as
pain, dreams, remembering, action, and reasoning
as exemplifying different modes of individual con-
sciousness. The concept of consciousness was largely a
product of individualism, of the various movements
such as Stoicism, Epicureanism, and Christianity,
which supplied types of conceptual schemes that were
very different from those which were appropriate to
the shared life of the city-states. The coordinating
concept of individual consciousness was not made ex-
plicit until it found expression in the systems of Saint
Augustine and Descartes. The use of introspection as
a technique for investigating consciousness went along
with such systems of thought, and behaviorism can only
be understood as a reaction against such a technique.
It would, therefore, be absurd to search for hints of
the central doctrine of behaviorism in a thinker such as
Aristotle, whose way of thinking about human life
antedated the conceptual schemes which permitted
such questions to be raised.

What can be said about Aristotle is that, being a
marine biologist by training, he was the first to ap-
proach the study of human beings in an objective and
systematic way. He developed a classificatory system
which included plants, animals, and man as belonging
to the same genus of living things. He sent his research
workers all over the known world to provide him with
facts, not only about the different species of living
things but also about the different types of customs
and systems of government under which men lived.
This was all recorded and fed into the classificatory
system that he developed at the Lyceum.

When, however, we turn to Aristotle's Metaphysics
and De anima, and study the conceptual scheme which
he thought appropriate for describing and explaining
human behavior, we find not just that his doctrine of
form and matter was incompatible with the materi-
alism espoused by many behaviorists but that, in his
psychology, he was an explicit critic of the mechanists
of his day.

Aristotle held that a living thing is a “body with
a soul,” “soul” designating the self-originated tendency
of living things to persist towards an end. This tendency
can be exhibited at the nutritive and reproductive level
as in plants, at the level of sensation and movement
as in animals, and at the rational level as in man.
Aristotle accused mechanists such as Democritus and
Empedocles of the all-pervading mistake of concluding
from the fact that the soul is the cause of movement,
that it is itself moved. He maintained that the soul
moves the body “by means of purpose of some sort,
that is thought.” Thinking is not a sort of motion any
more than desire or sensation are. His predecessors had
misunderstood the sort of concept that “soul” was.
Insofar as it is a capacity, how could it be moved?
A capacity is not the sort of thing that can be moved.
Insofar as it is an exercise of a capacity, such as think-
ing, it is manifest in a process that cannot adequately
be described as a change in motion. Aristotle deployed
many ingenious arguments to substantiate this criticism
of mechanical theories, many of which are similar to
those which can be found in the work of modern
philosophers such as Ryle (Peters [1962], pp. 102-04;
Ryle [1949]).

There are thus almost no grounds for linking Aris-


totle with behaviorism either in respect of its central
doctrine or in respect of its more peripheral ones. If
Aristotle is to be linked with any school in twentieth-
century psychology the obvious one would be that of
the “hormic” (purposive) psychology championed by
William McDougall. For here too we find behavior
studied objectively, an exaltation of purpose as the
most important explanatory concept, and a vehement
attack on the mechanists of his day, namely J. B.
Watson and the reflexologists. Indeed McDougall's
indebtedness to Aristotle is explicitly acknowledged at
many points.

2. Hobbes. There would be more plausibility in
attempting to trace behaviorism back to Hobbes than
to Aristotle. To start with, Hobbes was one of the great
thinkers of individualism and wrote at a time when
the private world of the individual was both recognized
and valued—and threatened by tendencies towards
absolutism. Hobbes himself regarded man's capacity
to form “phantasms” or images as one of his most
miraculous powers. “Of all the phenomena or appear-
ances which are near to us, the most admirable,” he
says “is apparition itself, τὸ αάινεσθαι ; namely, that
some natural bodies have in themselves the pattern
almost of all things, and others of none at all” (Hobbes
[1839a], p. 389). It was man's mysterious power to
register within himself what was going on around him
and to store up his impressions for use on further
occasions that awakened Hobbes's passionate curiosity.
How could this mysterious power be explained? This
was the problem that lay at the heart of Hobbes's
psychology and theory of nature.

Thus Hobbes's starting point in psychology reveals
both the conceptual possibility of behaviorism for him
and also the absurdity of thinking that, in the most
important respect, Hobbes was in fact a behaviorist;
for no behaviorist could regard the problem of imagery
as the most important phenomenon for a psychologist
to explain. It is also difficult to see how much could
be done about explaining it without constant resource
to introspection.

On the central question of the appropriate data for
a science of human behavior Hobbes was, as a matter
of fact, absolutely explicit. In his Introduction to
Leviathan he wrote:

But let one man read another by his actions never so
perfectly, it serves him only with his acquaintance, which
are but few. He that is to govern a whole nation, must read
in himself, not this or that particular man; but mankind:
which though it be hard to do, harder than to learn any
language or science; yet when I shall have set down my
own reading orderly, and perspicuously, the pains left an-
other, will be only to consider, if he also find not the same
in himself. For this kind of doctrine admitteth no other

(Hobbes, 1839b, Introduction).

Hobbes not only extolled introspection as the appro-
priate method for investigating mankind; he also
pointed to the unreliability of inferences made on the
basis of the observation of others. Since Hobbes ac-
cepted the use of introspective evidence, why has his
linkage to behaviorism seemed so plausible to so many?
There are, first of all, some underlying assumptions
which are common to the views of Hobbes and modern
behaviorists, and these are so deeply embedded in
modern thought that we tend to take them for granted.
The first is the assumption that there is some reliable
method for advancing knowledge. Hobbes was one of
the many “new men” of the post-Renaissance period
who believed that knowledge of nature was available
to anyone who was prepared to master the appropriate
method. He thought that Copernicus and Galileo had
revealed the method for investigating the natural
world, that Harvey had applied this to the study of
the body, and that he, Hobbes, was showing how this
method, the resoluto-compositive method of Galileo,
could be applied to psychology and politics.

Hobbes's early contact with Francis Bacon, for
whom he had worked for a period as a kind of literary
secretary, had also convinced him that knowledge
meant power. Hobbes's psychology and politics were
constructed with a very practical end in view—the
preservation of peace, and he thought that there was
no hope for England, in the throes of civil war, unless
those who had some influence on the course of events,
could be persuaded to accept the logic of his demon-
strations concerning man and civil society. This practi-
cal concern underlying his theorizing, which was later
to be applauded by Marxists, was another underlying
link between Hobbes and the behaviorists.

A much more explicit link between Hobbes and the
behaviorists was his materialism, and his attempt to
extrapolate the concepts and laws of Galileo's me-
chanics to the human sphere. “For seeing life is but
motion of limbs... what is the heart but a spring;
and the nerves but so many strings; and the joints but
so many wheels, giving motion to the whole body, such
as was intended by the artificer” (Hobbes, 1839b,
Introduction). Desires and aversions are motions to-
wards and away from objects. Thinking is but motion
in some internal substance in the head and feeling is
movement about the heart. Imagery, which he found
so wonderful, was to be viewed as a kind of meeting
place of motions. The phenomena of perception and
imagination could be deduced from the law of inertia.
In order to make such deductions Hobbes postulated
infinitely small motions, which he called “endeavours,”
in the medium between the object of sense and the
brain, and he had recourse to them also to explain how
movements coming from outside bodies are passed on
through the body so that they eventually lead to the


gross movements observable in desire and aversion.

Within behaviorism it is customary, following
Tolman, to distinguish between molecular and molar
theories of behavior. A molecular theory, such as that
of Clark Hull, is one which starts from postulates at
the physiological level and attempts to deduce the
movements involved at the molar level, e.g., the gross
movements of the body, from them. Hobbes antici-
pated such molecular theories to an astonishing extent
(Peters and Tajfel, 1957). But such anticipation had
nothing to do with behaviorism in a strict sense. It was
rather the consequence of applying the hypothetico-
deductive procedure of Galileo, together with his me-
chanical concepts and laws, to the realm of human
behavior. Hull, combined this Galilean approach to
psychology with the restriction of data to what could
be publicly observed, which was the central feature
of behaviorism (Hull, 1943). Hobbes, therefore, can
properly be regarded as the father of mechanistic
theories in psychology rather than of behaviorism; for
not all behaviorists were mechanists, and Hobbes him-
self relied on introspection in the psychological sphere.

3. Descartes. It would be more absurd to regard
Descartes as a behaviorist than Hobbes; for he was
notorious for the dualism of mind and matter which
he postulated. But, as a matter of fact, both his dualism
and his assumptions about scientific method did much
to create the climate of opinion which made behav-
iorism possible, if not almost inevitable.

Descartes held that there are two sorts of substances
in the world, mental and physical. If the behavior of
these substances was to be scientifically studied, as-
sumptions about them had to be made explicit and
exhaustively analyzed until clear and distinct ideas
were arrived at, which were simple in the sense that
no further analysis of them was possible. In the case
of ideas about material objects, for instance, the scien-
tist eventually arrived at the simple ideas of extension,
figure, and motion. If certain of these simple ideas were
combined, relationships could be grasped between
them which served as postulates for a deductive system,
as in geometry. Thus the understanding of bodies and
of minds respectively rested upon clear and distinct
ideas which had no features in common. Descartes'
problem about the relationship between mind and body
derived from the fact that, though in our confused
everyday experience we are aware of interaction, as
when our limbs move because of our intentions, no
clear and distinct idea can be formed of the manner
of this union. Such perspicuous ideas are only forth-
coming in the spheres of the mental and the physical
when they are proceeding independently of each
other—as in logical reasoning on the one hand or in
reflex movements on the other.

Descartes' dualism and his assumptions about scien
tific method thus gave rise to two traditions of enquiry
which came to be pursued more or less independently
of each other. On the one hand the human body, which
was regarded as functioning mechanically right up to
the level of instinctive behavior and simple habits, be-
comes a fit subject for objective study. Harvey had
made a splendid advance in this field with his mechan-
ical theory of the circulation of the blood. On the other
hand, the mind, by which Descartes meant mainly the
higher thought processes and the will, could only be
studied introspectively. The consequence of Descartes'
dualism was, therefore, the school of mechanistic biol-
ogy and reflexology on the one hand and the intro-
spective school of psychology on the other, which
reached its culmination about 250 years later in the
laborious experimental work of Wundt and Titchener.

It was against the assumptions of the introspective
school that Watson revolted—their assumptions about
both introspective method and the “stuff” of conscious-
ness which he claimed they were trying to study by
this method. And when he revolted he fell back on
the other tradition stemming from Descartes: mecha-
nistic biology and reflexology. All he did was to at-
tempt to extend its domain to the level of thought and
action which had previously been regarded as “mental”
and hence to be studied by introspective methods. And
when Watson theorized about behavior he was un-
wittingly Cartesian in his approach. He thought that
the complex phenomena of behavior could be ex-
plained by analysis into clear and distinct units of
behavior—simple reflexes.

4. Reflexology. Descartes' dualism involved the as-
sumption that the behavior of the body, below the level
of willed action, could be explained mechanically. He
had, however, a crude idea of how the body works.
He thought of it as a statue or machine made of earth
and was much impressed by the feats which mechanical
manikins could be made to perform in the gardens
of the aristocracy by arranging water-pipes within
them. They could be made to move their limbs and
even to produce sounds like words. He thus pictured
the nervous system as a piece of intricate plumbing.
The nerves were thought of as tubes along which
“animal spirits,” which occupied an indeterminate
status between the mental and the physical, flowed
continuously. Changes in the motion of these spirits
cause them to open certain pores in the brain. When
this happens the motion of the animal spirits is changed
and they are “reflected” into the muscles which move
the body. For he thought that many movements of the
body are not brought about by conscious intention, but
by an undulatio reflexa, or a movement of rebound
in the animal spirits at the meeting of the sensory and
motor channels at the pineal gland, where the mind
could also influence the body by means of images. The


automatic reactions of the body, which were not under
voluntary control, were thus called reflexes.

Little was done to refine this conception until 1811
when Charles Bell published a paper entitled “An Idea
of a New Anatomy of the Brain,” which he communi-
cated to the Royal Society in 1821, and in which he
claimed that the nerves, which are connected with the
spinal centers by anterior roots, are employed in con-
veying motor impulses from the brain outward, and
that the sensory nerves are connected with the poste-
rior roots of the spinal cord. This was confirmed by
Magendie in 1822. In 1833 Marshall Hall demonstrated
clearly the existence of reflex action which proceeded
independently of conscious volition, and in the latter
part of the nineteenth century the antics of animals
deprived of their higher brain structure were a com-
monplace. In 1851 Claude Bernard pioneered physio-
logical work on the influence of specific nerves on the
blood vessels and the consequent changes throughout
the sympathetic system, thus helping to understand the
connection between the brain and the viscera and other
changes involved in emotional and motivational states.
Evolutionary theory, especially that of Herbert
Spencer, led Hughlings Jackson to postulate different
levels of evolution in the nervous system from the less
to the more organized, from the automatic to the

From the point of view of the history of behaviorism
the crucial step forward was taken by Pavlov, whose
particular interest was in the digestive system. In 1897
he published a book on The Work of the Digestive
in which he noted that there are certain ir-
regularities and interruptions in the work of these
glands, which he attributed to psychic causes, e.g., that
sometimes the glands would start to work before food
was given to a dog, when the dog saw the man who
usually fed it. In 1902 he embarked on a long series
of experiments to study such phenomena. He concen-
trated on salivation, rather than on gastric secretion,
because it was more accessible to experimental analy-
sis. A dog was strapped in a test frame, with elaborate
experimental controls, and a bell (conditioned stimulus)
was repeatedly sounded before food (unconditioned
stimulus) was placed in the mouth to produce salivation
(unconditioned response), until eventually the sound
of the bell brought about salivation (conditioned re-
sponse) before the presentation of the food. Pavlov also
found that the conditioned stimulus becomes general-
ized, in that the dog comes to respond to a wide range
of stimuli. He found, too, that dogs could be taught
to discriminate between stimuli by rewarding responses
to one stimulus, such as a circle, but not to another,
such as an ellipse. If the difference between the stimuli
was gradually reduced a point would be reached where
the dog's behavior evinced all the symptoms of acute
neurosis. The concept of “reinforcement” was invented
to refer to this process in which the conditioned stimu-
lus is presented in close juxtaposition to the uncondi-
tioned stimulus. Many have commented on the simi-
larity between this concept and that of Thorndike's
“reward,” central to his law of effect. But the two
concepts emerged from very different theoretical
backgrounds and their differences are as important as
their similarities (Wolman [1960], pp. 53-55).

Pavlov was unrepentantly a physiologist and he
linked his experimental findings with a theory about
irradiation and processes of excitation and inhibition
in the brain. He expressed contempt for psychology
and refused to take sides in psychological controversies.
Nevertheless his influence has been nugatory in physi-
ological theory but vast in psychology, because the
behaviorists later seized upon his findings. His contem-
porary, Bekhterev, on the other hand, who also popu-
larized the conditioned reflex, was more catholic in
his interests. In 1907 he published his Objective Psy-
in which he proclaimed that the future of
psychology depended upon objective, external obser-
vation. He envisaged excluding introspective data and
mentalistic concepts and basing psychology on physical
and physiological findings. In this respect Bekhterev
harped back to La Mettrie and the materialistic tradi-
tion in psychology. In his conditioning experiments he
did not confine himself to reactions such as salivation
but met with some success in conditioning motor re-
sponses as well. He also took an interest in speech,
as also did Pavlov towards the end of his life.

Watson embarked upon his behavioristic program
in ignorance of the physiological studies of Pavlov and
Bekhterev, but he gradually incorporated them into
his theory when he became familiar with them through
translation. Thus Watson's reflexes functioned in his
theory as the direct descendants of Descartes' “simple
natures” in the bodily sphere. The links between them,
however, namely the principles of association, and the
assumptions about how generalizations could be ar-
rived at about such links, came from another source—
the empiricist tradition. A brief exposition of the lead-
ing ideas of this tradition will complete the account
of behaviorism's intellectual ancestry.

5. The Empiricist Tradition. The other aspect of
Descartes' thought, the interest in the contents of con-
sciousness, was developed by both rationalists and
empiricists alike. The empiricists, like the rationalists,
were really preoccupied with problems of knowledge.
As John Locke put it, they were concerned with the
“original, extent, and certainty” of human knowledge.
They held, however, that knowledge was based on
experience, not in the unexceptionable sense that how-


ever we come to obtain beliefs about the world, their
truth or falsity must be tested by comparing them with
what can be observed, but in the much more dubious
sense that our ideas about the world originate in our
own individual sense-experience. Therefore, questions
about the extent and certainty of knowledge tended
to resolve themselves into speculations about how ideas
originated; for followers of what was called “the way
of Ideas” held that genuine ideas must be tracked back
to impressions of sense. The result was that philo-
sophical questions about the meaning of terms and
about the grounds of knowledge were systematically
confused with questions in genetic psychology about
their origin. It was not until the nineteenth century,
when F. H. Bradley proclaimed that “In England we
have lived too long in the psychological attitude”
(Bradley [1922], 1, x) that this confusion, which per-
sisted from Locke to James Mill and Alexander Bain,
began to be systematically exposed.

The net result of this confusion was that the work
of the empiricists contained both a philosophical the-
ory about the grounds and acquisition of knowledge
and a psychological theory about the working of the
mind. The philosophical theory came straight from
Francis Bacon. To obtain knowledge, it was held, a
start had to be made with simple uninterpreted data,
or impressions of sense. There must be no premature
hypotheses or “anticipations of Nature.” Generaliza-
tions had to be made which reflected regularities in
the data. Bacon elaborated tables of co-presence, co-
absence, and co-variation of instances to ensure that
these generalizations were well-founded. These were
later elaborated by Mill in his celebrated methods of
experimental enquiry. It was of cardinal importance
in this process of “induction” that generalizations
should not go beyond the data and that no recourse
should be made to unobservables. Laws expressed
correlations between what could be observed.

The psychological theory which developed pari-
with this philosophical theory about the grounds
and acquisition of knowledge had two main features.
Firstly it maintained that the experience, thought, and
consequent action of the individual is caused from
without. The environment causes simple ideas (Locke)
or impressions (Hume) to arise in the individual. The
individual's body was also regarded as part of the
external world which gives rise to impressions of
reflexion—e.g., of pleasure and pain—which enter the
mind through different types of receptor. (This was
later on called “the inner environment” by behavior-
ists.) Secondly it was held that the ideas arising from
these two environmental sources become linked to-
gether by principles of association such as contiguity
and resemblance. Action is initiated by an idea that
has become linked with pleasure or pain. Thus food,
for instance, gives rise to an idea in the mind, which
has become linked to the idea of eating, which in its
turn has been linked with the idea of pleasure. This
brings about the action of eating the food. This account
of the initiation of action can be found in Hobbes,
though he did not give much prominence to the associ-
ation of ideas in his account of thinking. He stressed
the importance of plans deriving from desire.

The history of empiricism is largely the history of
the elaboration and sophistication of these basic ideas.
In the philosophical and methodological sphere there
were three main derivative doctrines. Firstly the notion
of “data” was gradually sophisticated into modern
theories of sense-data, which can be found in the work
of philosophers such as G. E. Moore, Bertrand Russell,
and A. J. Ayer. In the scientific sphere Kant did much
to popularize the idea that the domain of science was
coextensive with the domain of the measurable. It
became important, therefore, for scientists to obtain
data which were as precise and pure as possible by
devising various forms of measurement. In psychology
the nineteenth-century concentration on psycho-
physics, stemming largely from the work of Weber and
Fechner, bore witness to this search for measurable
data—the notorious just noticeable differences.

Secondly, a theory of meaning developed which has
come to be known as “logical empiricism.” This main-
tained that only those terms are strictly meaningful
that can be cashed by reference to what can be ob-
served. The language of morals and of poetry is, strictly
speaking, meaningless (or has merely “emotive mean-
ing”) because it cannot be tied down in this way to
observables. Scientific terms have either to be “opera-
tionally defined” or related indirectly to observation
by a process of “logical construction.” In the early
twentieth century P. W. Bridgman's book The Logic
of Modern Physics
(1927) popularized this view of
scientific terms. Its leading ideas were applied to psy-
chology by C. C. Pratt in The Logic of Modern Psy-
(1939) and exerted a considerable influence on
B. F. Skinner, a leader of modern behaviorism.

The third development was the attempt to formulate
precisely the methods for arriving at well-founded
generalizations and to get clearer about the theory of
probability which was presupposed. The works of J. S.
Mill, W. E. Johnson, and J. M. Keynes were classics
in this tradition.

The psychological theory which was favored by most
of the empiricists was given an ambitious start by
David Hume who pictured himself as the Newton of
the sciences of man. Simple impressions were regarded
as mental atoms and the principles of association were
postulated as performing, in the mental sphere, the


same function of uniting them together as was per-
formed by the principle of gravitational attraction in
the physical sphere. David Hartley developed an even
more ambitious version of this type of theory; for he
held that the psychological principles of association
paralleled the mode of operation of physiological
disturbances in the substance of the nerves, spinal
marrow, and brain, which he called “vibrations.” It
was left to James Mill, however, to free associationism
from Newtonian pretensions and physiological specu-
lation and to attempt to formulate soberly and prosa-
ically the basic principles in terms of which ideas were
thought to be connected. Most of the subsequent work
in the nineteenth century of the British associationist
school consisted in criticism, refinements, and simpli-
fications of Mill's edifice.

In France, largely through the infectious cynicism
of Voltaire, British empiricism came to exert an in-
fluence that was more mundane, and less theoretical.
It encouraged thinkers to observe more carefully and
more objectively how men in fact behaved. Diderot's
Lettre sur les aveugles and Lettre sur les sourds et muets
were classics of their kind—concrete case studies of
individual lives. Similarly Condillac approached
Locke's problems in a more concrete, if more imagina-
tive way, by creating the fiction of a statue endowed
only with the faculty of smell. And Cabanis, a vehe-
ment critic of Condillac, began his psychophysiological
writings in 1795 with an attempt to answer the con-
crete, if depressing question, of whether the victims
of the guillotine suffer any pains after decapitation.
His theory, which attacked Condillac's starting point
of imagining a being capable of sensation in isolation
from the structure of the organism as a whole, was
diametrically opposed to the atomism of the associa-
tionist tradition. But it was a theory based on actual
observations of men from childhood to maturity. Simi-
larly, La Mettrie, who elaborated Hobbes's thesis that
man is a superior type of machine, developed his the-
ory not as an imaginative extrapolation from Galilean
mechanics but partly as a result of his medical studies
under Hermann Boerhave, and partly from direct ob-
servation of his own experiences during a fever. And
in the nineteenth century Taine, who represented very
much the antimetaphysical, positivistic school in
France, scrambled together, in his De l'intelligence
(1870; trans. as On the Intelligence, 1871), reports from
asylums, physiological facts, and references to Mill's

It would be tempting to suppose that this interest
in the concrete behavior of men, and the attempt to
study it objectively, which was so characteristic of
French empiricism, was one of the formative influences
in the development of behaviorism. There is, however,
little plausibility in this suggestion. For the rise of
behaviorism is to be explained partly as a method-
ological reaction to introspective psychology and
partly as a consequence of the success which was being
attained in the study of animals. Almost the last thing
which the behaviorists actually came to study was the
concrete behavior of men. Let us now pass, therefore,
to the immediate origins of behaviorism.


J. B. Watson was by no means the first to see the
importance for psychology of the objective study of
behavior. William McDougall, in his Physiological
in 1905, had defined psychology as “the
positive science of the conduct of living creatures” and
had resisted the tendency to describe it as the science
of experience or of consciousness. In 1908, in his Intro-
duction to Social Psychology,
he explicitly introduced
the term “behavior” claiming that psychology was “the
positive science of conduct or behavior.” He main-
tained that psychology must not regard introspective
description of the stream of consciousness as its whole
task. This had to be supplemented by comparative and
physiological psychology relying largely on objective
methods, the observation of man and animals under
all possible conditions of health and disease. Similarly
in 1911 W. B. Pillsbury, a pupil of Titchener, published
his Essentials of Psychology in which he claimed that
psychology should be defined as “the science of human
behavior.” But neither McDougall nor Pillsbury put
forward a puritanical or restrictive position. They were
merely arguing that the objective study of animals and
of physiology had a lot to contribute to psychology.
It was therefore unwarranted to give a definition of
psychology which excluded their findings from the

What was distinctive about Watson's view of psy-
chology was what it excluded rather than what it
included; for McDougall himself was a devotee both
of physiology and of animal studies. Watson was deter-
mined to rule out introspection as a legitimate method
of obtaining data and to banish “consciousness” and
other mentalistic terms from the conceptual scheme
of his new science. What led him to this methodolog-
ical puritanism?

1. Animal Psychology. From the time of Darwin's
Origin of the Species (1859) and Expression of the
Emotions in Man and Animals
(1872) there had been
a growing interest in the behavior of animals, birds,
and insects in order to test his hypothesis of the con-
tinuity between animals and man. In 1872, for instance,
Spalding had studied swallows in order to determine
whether they learnt to fly by imitation or whether they


had an inborn tendency to do so. Between 1879 and
1904 Fabre had made a long series of observations on
insects to determine how much of their behavior was
due to instinct. The thesis that intelligence is continu-
ous between animals and men was examined by
Romanes, Lloyd Morgan, and Loeb on the basis of
observations of animal behavior. But the decisive step,
from the point of view of the rise of behaviorism, was
taken when in 1896 E. L. Thorndike introduced cats,
dogs, chickens, and monkeys into the laboratory and
carried out experiments on them in order to determine
how they learn. From the gradual, though irregular,
improvements in the learning curves Thorndike in-
ferred that the animals could not learn by “insight”
or by reasoning. Imitation was ruled out by experi-
mental controls. “Trial and error” seemed the only
possibility left. The animals, he suggested, went
through a variety of responses. Gradually the unsuc-
cessful responses were eliminated and the successful
ones were stamped in.

Thorndike believed that there were two basic laws
which explained this process. The law of exercise
maintained that connections were strengthened by use
and weakened by disuse; the law of effect maintained
that connections, which were rewarded and thus led
to satisfaction, were strengthened. This was not a par-
ticularly original theory, as the principles employed
were a commonplace in the associationist tradition.
What was original was his application of such princi-
ples to the connections between stimulus and response
and the experimental evidence from his laboratory
which he provided to support his view.

Watson, significantly, started his academic career in
philosophy, but switched to psychology during his
period of graduate study at the University of Chicago,
and devoted himself to animal psychology. In 1908
he became professor of psychology at Johns Hopkins
University and in 1912 he launched his polemic in some
public lectures which were eventually published in
1914 in his book entitled Behavior. The vehemence
of his attack was to be explained partly by his resent-
ment of the grudging and slightly condescending atti-
tude of most orthodox psychologists of the day towards
animal studies. Instead of putting a reasoned case, as
did McDougall and Pillsbury, for the importance of
animal studies and physiology for psychology, Watson
pointed a derisive finger at the state of introspective
psychology. “Today” proclaimed Watson “the behav-
iorist can safely throw out a real challenge to the
subjective psychologists—Show us that you have a
possible method, indeed that you have a legitimate
subject-matter” (Watson [1924], p. 17). This jibe was
occasioned by the “imageless thought” controversy
amongst introspectionists and other examples of diver
gent results obtained in different laboratories by well-
trained introspectionists. Watson confidently asserted
that psychology could only become a science, instead
of a debating society, if the methods were used which
had proved so successful in animal laboratories.

2. Inductivism. The second positive starting point
of behaviorism was the view about scientific method
which Watson shared with the introspectionists whom
he attacked. Wundt and Titchener, the giants of the
introspective school, had been vehement in their am-
bition to base psychology on properly controlled ex-
periments. The general appeal to look into oneself in
order to decide upon psychological questions, which
one can find, for instance, in the controversies between
Locke, Berkeley, and Hume, was not good enough.
Introspective observers had to be carefully trained.
Moreover Titchener argued that they had to be trained
to distinguish pure experience as “existences” from the
“meaning” which it has for men in their ordinary lives.
Unless this could be done psychology would never
arrive at any pure data on which a science of mind
could be created.

This presupposed a certain view of scientific method,
dating back to Bacon, which is often called “induc-
tivism” or “observationalism” (Popper, 1962). The
leading idea of this conception can be summed up in
Titchener's own words: “We are agreed, I suppose, that
scientific method may be summed up in the single word
'observation'; the only way to work in science is to
observe those phenomena which form the subject-
matter of science” (Titchener [1908], p. 175). Watson
himself had basically the same conception of scientific
method. To quote him: “You will find, then, the behav-
iorist working like any other scientist. His sole object
is to gather facts about behavior—verify his data—
subject them both to logic and mathematics (the tool
of every scientist)” (Watson [1924], p. 7). Watson's
basic objection to introspectionism was that it was an
attempt to form a science on very unreliable data about
which experimenters could reach no agreement, and
which purported to reveal facts about a nonexistent
subject matter, namely consciousness. If psychologists
were to start from data provided by rats in mazes they
would at least have a chance of developing a science
on the basis of publicly observable data.

When it came to making generalizations Watson
again showed his inductivist allegiance; for the Baco-
nian view was that generalizations should never go
beyond the data. They should simply record correla-
tions between observables. Thus Watson was as unin-
terested in physiological speculation about intervening
processes as he was hostile to any recourse to unob-
servable mental entities or processes to explain what
could be observed. One should, of course, quantify the


data if possible and operate mathematically on it. But
this was merely a way of arriving at correlations.

3. Associationism. The correlations which Watson
discerned were again part and parcel of the introspec-
tionist tradition, namely, the laws of association. He
did not reject the postulate of instincts, but accorded
them less and less importance in comparison with the
influence of the environment via learning. In his theory
of learning he rejected Thorndike's law of effect be-
cause the concept of “satisfaction” was mentalistic. He
relied on the law of exercise under which Thorndike
had subsumed the old principles of association such
as frequency and recency. He also minimized the im-
portance of the brain and of central processes in learn-
ing. All behavior, he believed, was sensori-motor, con-
sisting of stimulus-response units. It was initiated by
the stimulation of a sense organ and terminated in a
muscular or glandular response.

Thorndike produced conclusive evidence to demon-
strate the inadequacy of the law of exercise as a suffi-
cient explanation of learning, but Watson kept his head
above water by incorporating into his theory the pos-
tulate of the conditioned response which Pavlov had
first put forward in 1902. This, together with the con-
cept of reinforcement, gave a more acceptable account
of the type of strengthening of connections which
Thorndike had covered by his mentalistic law of effect.
But it was only gradually that the work of Pavlov and
of Bekhterev, who put forward a similar theory of
associated reflexes at about the same time, became
known in America. It seems as if Watson was familiar
with the Russian work from about 1914 onwards but
he only gradually grasped its importance for his theory.
By 1924 he had come to entertain the view that the
conditioned response might afford the key to all habit
formation. Other behaviorists, however, took over the
conditioned response with alacrity. Indeed, in a modi-
fied form, it kept their theory going for about a quarter
of a century as will later be explained.

If Watson had stuck rigidly to what could be exter-
nally observed he would have severely restricted his
“subject-matter.” However he claimed that thinking
could also be studied because it consisted in implicit
speech reactions or in subvocal talking. The implicit
behavior, which constitutes thinking, becomes substi-
tuted for overt manipulation. The child begins by
learning to name things that he is doing while he is
doing them, speech being a series of conditioned re-
sponses. He then learns to do this inaudibly and as a
substitute for doing them. Thinking is therefore surro-
gate behavior.

Watson also contrived to include emotions within
his subject matter by claiming that they consisted in
implicit visceral reactions. He espoused the James-
Lange theory, while disregarding the introspective
feelings which James claimed to be consequent on the
visceral changes. In his actual studies of emotion, how-
ever, he rather ignored their visceral source and con-
centrated on their overt manifestations. He singled out
three emotions—rage, fear, and love—as being innately
determined, and suggested that all others are acquired
by conditioning. He achieved some fame, or notoriety,
by showing how small children can be conditioned to
develop aversions to harmless animals like rabbits and
white rats, if their appearance is associated with a
noxious stimulus such as a loud noise.

Thus on the slender basis of the conditioning of
reactions such as salivation and simple movements, of
a bizarre and quite dubious theory of thinking, and
of a few interesting experiments in conditioning chil-
dren's emotional reactions, Watson made optimistic
claims for what could be achieved in education and
social life generally by a process of systematic and
benevolent conditioning. His doctrine fitted well with
the thinking of a nation one of whose basic problems
was to create American citizens out of a multitude of
immigrants of diverse origins, and who, in their ap-
proach to life combined a pragmatic outlook with a
high level of technical skill, and a friendly extroverted
disposition with an optimistic attitude towards the


It has been argued that behaviorism was basically
a methodological movement in psychology which laid
down restrictions on the data on which a science could
be properly based. In the case of its founder, J. B.
Watson, this central doctrine was supported by an
inductivist view of scientific method flanked by the
metaphysical doctrine of materialism and by the asso-
ciationism of a peripheralist, or S-R, type as a psycho-
logical theory. Few of the later behaviorists shared all
these assumptions. In commenting, therefore, on the
main features of their theories special attention will
be paid to their adherence to or departure from these
other tenets of Watson which have come to be loosely
associated with behaviorism.

1. Early Materialists. Some of Watson's more im-
mediate contemporaries had more in common with his
bold, metaphysical brashness, than his later followers.
Albert P. Weiss, for instance, published a book entitled
A Theoretical Basis of Human Behavior in 1925 in
which he banned consciousness and introspection from
psychology and claimed that all behavior could be
interpreted in terms of physiochemical processes. Nev-
ertheless he argued that what is distinctive of a human
being is that his environment is social. Psychology is


therefore a bio-social science which is particularly
concerned with the impact of the social environment
on a biological organism. Weiss was particularly inter-
ested in child development and learning, but he never
seriously tackled the conceptual problems facing his
reductionism, of how features of the social environ-
ment, such as commands, promises, and moral exhorta-
tion can be analyzed in purely physical terms.

Another early behaviorist, who showed equal naiveté
about the environment, was W. S. Hunter. He held
that consciousness or experience for the psychologist
is merely a name which he applies to what other
people call “the environment.” This suggestion epito-
mizes the epistemological innocence of most of the
early behaviorists, against which Koffka reacted so
strongly. Hunter, however, distinguished himself in
other ways. He thought that the new look in psychol-
ogy deserved a new name and attempted, without any
success, to substitute “anthroponomy” for “psychol-
ogy.” He also was the first to use the temporal maze
for the study of motor learning.

A more ingenious and interesting theorist of early
behaviorism was E. B. Holt. He was one of the first
to try to deal with Freudian phenomena within a
behavioristic framework and his The Freudian Wish
and its Place in Ethics
(1915) is a classic in this tough-
minded tradition, which was later to include O. H.
Mowrer, J. Dollard, and N. E. Miller. Holt also devel-
oped Watson's idea that thinking is subvocal talking
and theorized about the connections between language
and conditioning. He thus anticipated later much more
ambitious, if abortive, attempts to exhibit language as
a system of conditioned responses.

Karl S. Lashley was a pupil of Watson's who made
distinguished contributions to the physiology of the
nervous system. This, however, did not prevent him
from making pronouncements about the subject matter
of psychology and about its methods, for instance, that
introspection is “an example of the pathology of scien-
tific method” (Lashley, 1923). His physiological find-
ings, however, as expressed in his Brain Mechanisms
and Intelligence
(1929), did not support other doctrines
of Watson. His postulates of equipotentiality—that one
part of the cortex is potentially the same as another
in its capacity for learning, and of mass action—that
learning is a function of the total mass of tissue, favored
a centralist theory of learning rather than Watson's
peripheralist theory. He became very critical of S-R
theories which postulated a simple connection between
stimulus and response and which ignored the role of
intervening cortical processes. The simple switching
function accorded by Watson to the brain, which he
inherited from Descartes, was denied.

Lashley, however, never departed from Watson's
materialistic standpoint. Like Weiss and Hunter he
believed that ultimately behavior could be describable
in the concepts of mechanics and chemistry. It is also
significant that all these early behaviorists shared an
inductivist view of scientific method. They thought of
the different sciences as having different subject mat-
ters and as consisting of generalizations about them
derived from reliable data drawn from these subject
matters. In this respect they shared not only Watson's
methodological recipes but also the view of scientific
method from which these recipes arose (Peters, 1951).

2. E. C. Tolman. One of the most influential and
forceful converts to behaviorism was E. C. Tolman;
for he was calling himself a “purposive behaviorist”
as early as 1920, though his definitive work entitled
Purposive Behavior in Animals and Man did not appear
until 1932. He aligned himself with the behaviorists
because he accepted their central methodological doc-
trine about the sort of evidence on which a scientific
psychology should be based. He did not indulge, like
Watson and Weiss, in metaphysical assertions about the
sorts of entities which there are in the world; he ad-
mitted that, at a common-sense level, men introspect
and manage well enough with mentalistic terms. What
he doubted, however, was the adequacy of this termi-
nology for scientific purposes. “Raw feels” are scien-
tifically useless, and mentalistic terms can be translated
into the language of observable behavior. Tolman, in
other words, was a conceptual behaviorist rather than
a materialist, as well as being a behaviorist in his
explicitly stated methodology.

In the conceptual sphere Tolman made at least three
contributions, two of which were of permanent impor-
tance. Firstly he called himself a purposive behaviorist
because he maintained that the concept of purpose was
irreducible. As has been mentioned (sec. I, 2), he dis-
tinguished between the molecular and the molar level
of behavior, whose unity as segments of behavior is
provided by the ends towards which movements persist
and in the attainment of which they are docile. He
accused Watson of not distinguishing clearly between
the molecular and the molar levels of analysis and
maintained, against Hull, that behavior at the molar
level is an “emergent” which has descriptive and de-
fining properties of its own. Descriptions of it cannot
be reduced to or deduced from analyses at the molecu-
lar level.

Secondly Tolman made rather bizarre attempts to
translate mentalistic terms, which had application at
the molar level, into a behavioristic type of termi-
nology. “Consciousness” became “the performance of
a 'sampling' or 'running-back-and-forth' behavior.” He
even suggested that Freudian personality mechanisms
can be translated into this type of terminology.


Thirdly, Tolman introduced into psychological the-
ory the notion of intervening variables. Terms like
“instinct” had previously been used, e.g., by
McDougall, not simply to postulate that certain pur-
posive behavior patterns were unlearned; they also had
a metaphysical dimension to them—a suggestion of
Aristotelian entelechies, of dynamic mental atoms ac-
tivating behavior. Tolman argued that it was perfectly
legitimate for a behaviorist to use a term like “drive”
which did not denote an unobservable entity, but
which was a shorthand symbol for stating a correlation
between antecedent conditions, e.g., food-deprivation,
and variations in behavior, e.g., eating.

This conceptual clarification helped to set psychol-
ogy free to theorize without fear of metaphysics. It
led on to the use of hypothetical constructs, which did
commit theorists to postulates about unobservables
usually of a physiological sort. (For this distinction see
MacCorquodale and Meehl, 1948.) Tolman thus con-
tributed to ridding psychology of the inductivist myth,
shared by the early behaviorists, that scientists must
never go beyond what is observed. In fact, however,
the postulation of unobservables to explain the ob-
served has been one of the most potent sources of
scientific advance.

In the details of his psychological theory Tolman was
eclectic. He stressed the importance of both demand
variables and cognitive variables in behavior, and at-
tempted to state more precisely assumptions of the sort
which McDougall had incorporated in his theory of
instincts, i.e., of innate dispositions to pay attention
to and behave in specific ways towards objects of a
certain class.

In his account of the demand variables Tolman dis-
tinguished first-order drives, which are linked with
specific antecedent physiological conditions and con-
sequent states of physiological quiescence (e.g., food-
hunger, sex-hunger) from second-order drives (e.g.,
curiosity, constructiveness) which are not so obviously
linked. This distinction, which was later to become that
between biological and acquired drives, was important
in the history of behaviorism. On the cognitive side
Tolman postulated “means-end readinesses” for
“means-objects” which are innate but docile relative
to the success of the organism in attaining its goal.
Also in his account of “behavior supports” he tried
to escape the sensory atomism of stimulus-response
psychology. He also developed the concept of the
“sign-Gestalt expectation” to incorporate the findings
of Gestalt psychology into his assumptions about the
organism's perceptual field.

Although Tolman emphasized the importance of
innate appetites and aversions in behavior he was
equally emphatic on the importance of learning, in
which he stressed the role of cognitive variables. He
argued, also, that the evidence of latent learning was
inconsistent with Throndike's law of effect. In trial and
error learning a refinement of sign-Gestalts takes place.
A kind of cognitive map develops of the different
possibilities as the various alternatives are explored.

Motivational variables are, of course, important in
learning in that they determine which aspects of a
situation will be emphasized. But learning depends
primarily on the expectancy of achievement and on
confirmations of the expectancy. In learning animals
and men make predictions and the maps which they
use to do this are refined more and more as experience
confirms or falsifies them. As Tolman developed his
theory he became more and more interested in and
convinced of the importance of cognitive variables. It
is therefore understandable that behaviorists became
increasingly embarrassed by Tolman's claim that he
was one of them.

3. C. L. Hull. Behaviorism was basically old philos-
ophy masquerading as a new scientific theory. In the
1930's philosophers began to be extremely critical of
the old inductivist view of scientific method, which
most of those in the empirical tradition had accepted,
though Whewell in the nineteenth century had been
an acute critic of this view. The role of hypothesis
and deduction in science, which had been so prominent
in the work of Galileo, was emphasized. Psychology
began to be influenced by this change of emphasis in
the philosophical climate. It was suggested, notably by
Kurt Lewin and by Clark Hull, that psychology was
in a state of disarray, split into warring factions, be-
cause it had not yet entered its Galilean phase. Lewin,
a Gestalt psychologist, wrote a detailed methodological
polemic to this effect in his chapter on “Aristotelian
and Galilean Modes of Explanation” in his A Dynamic
Theory of Personality
(1935). He envisaged the use of
the resoluto-compositive method of Galileo to erect
a field theory in psychology employing postulates taken
from dynamics.

Clark Hull, unlike other prominent behaviorists, was
not trained in an animal laboratory. He had established
a reputation for himself as an ingenious and talented
designer of experiments in concept formation, hypno-
sis, and suggestibility. He next turned to Pavlov's laws
of conditioning, and Hull's love for mathematics led
him to set up a hypothetico-deductive model of learn-
ing. He became more and more ambitious and revived
Hobbes's dream of a mechanical system in which the
laws of human behavior could be deduced from postu-
lates about “colorless movements” at the physiological
level. He accepted Tolman's distinction between mo-
lecular and molar behaviorism, but differed from
Tolman in thinking that behavior at the molar level


could ultimately be explained in terms of movements
at the molecular level. In 1943 he set out his ambitious
program in his Principles of Behavior, and in 1951 he
published a revised and more formalized version of his
system in his Essentials of Behavior.

There was little original in the actual content of
Hull's system save the appearance of exactitude created
by his technical constructs and mathematical form of
expression. Hull started from the biological postulate
of self preservation and maintained that the organism
is in a state of need when there is a deviation from
optimum conditions for survival, e.g., lack of food,
water, air. These needs are reduced by adaptive ac-
tions. The pattern of actions which lead to a reduction
of a need becomes reinforced—as in Thorndike's law
of effect. A stimulus which leads to a need-reducing
action may become associated with another stimulus
in accordance with principles of conditioning, though
Hull believed that there is no conditioning without

Hull acknowledged the importance of what Tolman
had called “intervening variables” in theory con-
struction, and also took over his concept of “drive.”
He regarded needs as producing primary animal drives,
which enabled him to correlate observable antecedent
conditions—e.g., of food deprivation with the energy
expended in behavior, e.g., in eating. He classified
drives on the Darwinian principle of whether they
tended towards survival of the individual organism or
of the species. Whereas, however, Tolman only postu-
lated such drives in order to explain the activation of
behavior patterns, Hull postulated them to explain
their acquisition as well, and their consolidation into
habits. Tolman, as has already been explained, was
critical of the law of effect. Hull, on the other hand,
tried to provide a mechanical theory to explain its
operation. He also rejected Tolman's emphasis on cog-
nitive variables and claimed that they could be derived
from his fundamental postulate of stimulus-response
association. Like Watson he was basically a periph-
eralist and an associationist in his orientation. He
merely attempted to formulate these assumptions more
precisely as part of a mechanical system.

Hull said that his book had been written “on the
assumption that all behavior, individual and social,
moral and immoral, normal and psychopathic, is gen-
erated from the same primary laws; and that the
differences in the objective behavioral manifestations
are due to the differing conditions under which habits
are set up and function” (Principles of Behavior, Pref-
ace, p. v). This was programmatic. In fact his defini-
tions and postulates were not well rooted in physio-
logical findings, and precise deductions to the level of
motor behavior were never made—if indeed they ever
could be made. Unobservables, such as drive-stimuli,
drive-receptors, etc., which were meant to fill in the
mechanical picture of the workings of needs and drives,
functioned more as hypothetical constructs relating to
entites whose existence was shadowy and whose inter-
relations were highly obscure. The main value of his
work was to formulate assumptions about animal
learning at the motor level in a precise enough way
to be refutable. And most of his assumptions were in
fact refuted, e.g., by Hebb, Young, Harlow, and others.
His system, however, became popular. Needs and
acquired drives proliferated which lacked even the
pretence of being anchored to physiological moorings
(Peters [1958], Chs. 4 and 5). Drive-reduction became
a classic example of twentieth-century metaphysics.

4. E. R. Guthrie. Hull had been content to state
empirical laws at the molar level in terms of actions
such as “biting the floor-bars” and “leaping the barrier”
on the assumption that laws at this level of description
could eventually be deduced from physiological postu-
lates. E. R. Guthrie, on the other hand, a contemporary
of Hull, eschewed physiological speculation and at-
tempted to reduce behavior at the molar level to
movements such as muscle contractions and glandular
secretions, between which correlations could be stated.
He claimed that all such correlations were derivable
from the old associationist law of contiguity namely
that stimuli acting at the time of a response tend on
their recurrence to evoke that response. He was an
S-R theorist par excellence.

Guthrie was one of the few behaviorists to stress the
difference between acts and movements. An act, he
claimed quite rightly, is a movement, or a series of
movements, that brings about an end and acts are
classified in terms of the ends which they bring about.
Learning, he argued, deals with movements, not with
acts. Thorndike's law of effect concerns acts, not
movements. It does not therefore deal with the basic
laws of learning which state correlations between
movements—e.g., between the stimulation of a sense
organ and a muscular contraction. In a famous experi-
ment which he did with Horton (Guthrie and Horton,
1946) he placed a cat in a box, release from which
was obtained by touching a pole in the middle of the
floor. It was demonstrated that the cat tended to repeat
the posture in which it first touched the pole and
obtained release. This experiment at least showed that
contiguity is an important principle of learning; it did
not establish that it is the only principle and later
experiments (e.g., by Seward) showed that improve-
ment in learning was brought about by providing an
additional reward. Whether Guthrie's experiment
showed anything about the wider issue of the impor-
tance of movements in learning as distinct from acts


is quite another question. It is significant that Guthrie
had to go to extreme lengths in constructing a situation
where no intelligence was required to escape from the
box, in order to make his reduction look in the least
plausible. Nevertheless Guthrie was an important figure
in the history of behaviorism because he at least saw
the importance of the distinction between movements
and acts, and because he saw it as an obstacle in the
path of any reductionist program.

5. B. F. Skinner. Skinner is the last survivor of the
great men of the behaviorist era, but in many ways
he is the most old-fashioned of all of them in his
methodology; for in Skinner we encounter the pure
strain of the inductivist doctrine of scientific method.
Skinner believes that a scientist must start from empir-
ical data and gradually move towards making inductive
generalizations or laws. Then, at some later stage, he
may be in a position to formulate a theory which unites
the laws. He must therefore be very careful to start
from reliable public data. Skinner admits that men
have “inner lives” which are of importance to them
as well as to novelists, as Skinner himself portrayed
in his novel Walden Two. But data drawn from this
source can never form a reliable basis for a science.
Skinner's polemics against other psychologists, such as
Freudians, who based generalizations on data drawn
from this inner realm, have been as forceful as Watson's
polemics against the introspectionists.

Skinner has also accepted the inductivist warning
that a scientist must never go beyond the observable
in order to explain the observed. He has had no more
use for physiological speculation about what goes on
inside the organism than he has had for mentalistic
constructs. He accords a limited importance to
Tolman's intervening variables such as “drive” pro-
vided that it is clearly understood that such terms are
shorthand symbols for designating the operations by
which the rate of responses can be measured. To speak
of hunger as a drive, for instance, is to pick out the
effects of operations such as deprivation on the proba-
bility of eating behavior.

Another significant feature of Skinner's approach is
his operationalism, which has recently been fashionable
as a theory about the language of science. (See I, 5
above and Peters, 1951.) To Skinner this meant “the
practice of talking about (1) one's observations, (2) the
manipulative and calculational procedures involved in
making them, (3) the logical and mathematical steps
which intervene between earlier and later statements,
and (4) nothing else” (Skinner [1945], p. 270). This
doctrine maintained that a term like “length” or
“hunger” refers not to a characteristic of an object or
to a state of an organism but to the experimenter's
operations of observing, manipulating, and measuring
it. It was an offshoot of positivism and of the verifica-
tionist theory of meaning which came to the fore
during the period between the two World Wars.

This theory of meaning has now been abandoned
by most philosophers. But it lives on in the meth-
odology of Skinner and some other behaviorists, where
it has the added appeal of being in line with the em-
phasis on control and manipulation of the environment
which was so characteristic of behaviorism in the
Watsonian tradition. Behaviorism was in many respects
an offshoot of American pragmatism. The experimenter
has not got to trouble his head with theoretical ques-
tions about why organisms behave as they do, espe-
cially if reference might be made to recondite inner
causes in order to answer them. It is sufficient to see
what forms of behavior develop if one environmental
variable is manipulated rather than another. This will
lead to predictions which will eventually enable the
experimenter to “shape” behavior.

Skinner claims that he has no “theory” of behavior
but only notes correlations. But this, of course, is either
naive or a matter of stipulation about the use of the
term “theory.” In fact his work has presupposed a
biological theory of a Darwinian type in which condi-
tioned reflexes are postulated as having survival value.
In formulating the laws in accordance with which these
“reflexes” are built up Skinner in fact revived many
of the established principles of associationist theory.

In formulating these laws Skinner made an important
distinction between “respondent” and “operant” be-
havior. This was facilitated by his introduction of the
Skinner box, which enabled him to study instrumental
conditioning in a much more controlled way than had
been possible in Thorndike's puzzle box. In a respond-
ent reaction there is a known stimulus, such as the
ticking of the metronome, with which a reaction such
as salivation can be correlated as in classical condition-
ing. In an operant response, however, such as lever
pressing, there are no known stimuli with which the
response can be correlated in this way. There may,
of course, be some form of internal stimulation, but
such speculations were ruled out by Skinner's opera-
tionalist approach. So operant responses must be re-
garded as functions of experimental conditions such as
food schedules which can be manipulated by the ex-
perimenter. As behavior consists largely of such oper-
ant responses, which are instrumental in obtaining a
variety of goals, Skinner thought that the study of
conditioned operants and their extinction must provide
the basic laws which would enable behavior to be
predicted and controlled. One day a theory might be
devised to unify these laws; but the scientist must
proceed to such “interpretations” in a Baconian man-
ner. He must not “anticipate” Nature by premature


theorizing—especially if this involves speculations like
those of Hull about the internal workings of the orga-
nism. Thus Skinner rejected the peripheralist approach
of Watson but has remained agnostic about the central
processes which mediate between stimuli and re-
sponses. Operant conditioning has been, in fact, an-
other way of reformulating Thorndike's Law of Effect,
in nonmentalistic terminology.

Like Watson, Skinner has not been averse to extend-
ing his conceptual scheme to cover other aspects of
behavior. For instance in his Science and Human Be-
in 1953 Skinner made pronouncements about
emotions, the names of which serve to classify behavior
with respect to various circumstances which affect its
probability. In spite, too, of his hardheaded positivistic
approach in his Verbal Behavior (1957), he outlined
an ambitious scheme for including language within the
behavioristic framework. This work, however, was just
about as programmatic as Hull's Principles of Behavior,
and has been severely criticized by philosophers and
linguists alike (Chomsky, 1959).

In recent times Skinner has been very much pre-
occupied with providing a technology of teaching in
which skills and sequences of material are carefully
broken down and the path of learning systematically
shaped by positive reinforcement. However, his con-
cept of “reinforcement,” which has always been criti-
cized for its obscurity and circularity, has undergone
such changes that his recipes for teaching amount to
little more than injunctions that material should be
logically analyzed and students should be taken
through it step by step in a way which minimizes the
repetition of mistakes, and which supplies constant
rewards for success. This type of procedure, as Skinner
himself has admitted, could be devised without much
reference to his elaborate laws of operant behavior.


It has been argued throughout this article that be-
haviorism, as an historical phenomenon, has been a
loosely knit collection of doctrines and theories woven
round a central prescription about the proper method
to use in developing a science of psychology. Behav-
iorism, first of all, has often been associated with the
metaphysical doctrine of materialism. Nowadays there
is less reluctance to discuss metaphysical problems than
there was in the heyday of behaviorism and of “the
revolution in philosophy” (Ryle, 1956). Materialism has
been revived, though it has few adherents amongst
philosophers (Smart, 1963; Armstrong, 1968). One of
its problems has been to state coherently what could
be meant by saying that mental and bodily processes
are identical (Hamlyn, 1964).

It would be difficult to maintain that, in the sphere
of scientific theory, behaviorism has advanced the un-
derstanding of behavior in any major respect. The
theory which was most widely employed was that of
associationism which was as old as Hobbes, Hume, and
Hartley. The behaviorists merely transferred this the-
ory from the realm of ideas to the realm of movements.
What occupied them most was disputes amongst
themselves within this type of theoretical framework.
There were two major issues which divided them. The
first related to the importance of reward or rein-
forcement in setting up S-R connections. The second
issue concerned the relative importance of central as
distinct from peripheral processes. It was not really
surprising that the behaviorists in fact contributed little
in the way of theory to the understanding of behavior;
for basically most of them were not interested in ex-
plaining behavior or even learning for that matter.
They were interested in conditioning. Even at the
animal level it is extremely doubtful whether rats, dogs,
cats, and monkeys in fact learn much by conditioning
in a normal environment. Ethological studies certainly
cast grave doubt on the omnipresence of this type of
learning. It is probable that this type of learning is
an artifact of the situations in which animals have been
confined. The extrapolation of this type of learning to
the human level, where the pattern of life is deter-
mined largely by social rules and purposes, was largely
programmatic. However, behaviorists showed that as-
sociationist principles might well apply to the learning
of simple reactions and motor habits. Little more could
in fact be claimed for their contribution to psycho-
logical theory.

Many of the defects in behavioristic theorizing, es-
pecially their programmatic extrapolations to the
human level, derived from their lack of clarity about
such concepts as stimulus, reinforcement, and response.
Underlying these particular confusions were funda-
mental confusions about the concept of behavior itself,
due to their aversion to assuming the existence of
consciousness. Guthrie was most sensitive to this diffi-
culty. He made the distinction between acts and
movements and tried to arrange an experiment which
dealt only with movements; for he realized only too
well that descriptions of behavior at the molar level
are in terms of acts and not in terms of mere move-
ments. And we identify their acts by reference to what
human beings have in mind when they make certain
movements. For example, an act involving the same
movements of the arm is identified as either signalling
to a friend or fanning the face (Hamlyn, 1953).

Skinner, in his distinction between operants and
respondents, actually hit upon a distinction which is
crucial for getting clearer about the concept of action.
Respondent reactions like salivations and eye-blinks,


which can be dealt with reasonably well by classical
conditioning theory, are indeed reactions which can
be correlated with stimuli. But they are not, strictly
speaking, actions; they are events that happen to us.
When, however, we pass to Skinner's operants, to
things done as instrumental to an end, we are entering
the sphere of action proper. Such actions, at the human
level at any rate, cannot either be described or ex-
plained as mere movements exhibited at the reflex
level. For an action is not simply a series of bodily
movements; such movements as are necessary to it are
done for the sake of something, as Aristotle pointed
out in his criticism of the mechanists of the ancient
world. They are classed as belonging to an action
because of their assumed relevance to an end (telos).

Similarly, on the perceptual as distinct from the
motor side of behavior, the importance of consciousness
is inescapable. Human beings, and probably animals
as well, do not often simply react to stimuli in terms
of their purely physical properties, as the Gestalt psy-
chologists pointed out in their distinction between the
psychological and physical or geographical properties
of the environment. They see things as meaning some-
thing; they respond to features of situations which are
interpreted in terms of their understanding of them.
Skinner, for instance, was grossly misleading when he
claimed that what we call emotions are names for
classifying behavior with respect to various circum-
stances which affect the probability of the behavior's
occurrence; for the circumstances are those which are
interpreted by the subject in a certain light, e.g., as
dangerous in the case of fear, as involving somebody
else having something which we want in the case of
envy. The relationship between circumstances and the
subject is not one of purely physical causality (Peters,

In brief even what the behaviorists called “behavior”
includes a range of phenomena between which there
are very important distinctions, let alone other purely
mental phenomena such as remembering and dream-
ing, which may have no overt expressions and which
may lead to no overt actions. Many more distinctions
than these can be drawn which would complicate the
picture even further. But this would not affect the two
cardinal points that need to be emphasized: first, that
it is impossible to make such distinctions without ref-
erence to consciousness and, second, that behaviorists
tend to think that the form of description and explana-
tion applicable at the lowest level of reflex behavior
can be extrapolated to explain the much more complex
phenomena at higher levels.

About the methodological doctrine that was the
kernel of behaviorism—that psychology should base
itself as a science on the type of publicly observable
data that biologists use when theorizing about ani-
mals—the first point to make is that it is an example
of the long-standing delusion that success in science
depends upon following a particular method. A study
of the history of science gives no support for the belief
that science has in fact been advanced by following
any particular method, if this is interpreted as meaning
following a particular procedure for making discoveries
or arriving at laws. It is impossible to formulate any
method for arriving at hypotheses; all that can be done
is to lay down general rules about testing them.

Is there then anything to be said for the behaviorists'
prescription as a procedural rule relating to the testing
of hypotheses rather than to their formulation? If they
had been concerned solely with animal behavior their
prescription would have been unexceptionable but
otiose; for there is no possibility of obtaining intro-
spective reports from animals. Insofar, however, as they
studied animals partly with the intention of making
extrapolations to human behavior, their prescription
seems to be very much a self-denying ordinance, for
in science it is advisable to obtain all the evidence
available. Also the sort of observations which are ap-
propriate depends upon what is being studied. If it is
reactions such as salivation, knee-jerks, and simple
motor skills, which were the main field of interest
amongst behaviorists, introspective reports may not be
of great significance. If, however, hypotheses about
dreams, perception, delusions, remembering, emotional
phenomena, or moral development have to be tested,
it is very difficult to see how much relevant evidence
could be accumulated without recourse to reports by
the subject. And it simply will not do to say that the
experimenter is then relying on another form of be-
havior, namely verbal behavior. Furthermore, this
move by behaviorists is a form of conceptual behav-
iorism. The methodological doctrine, which is distinc-
tive of behaviorism, would evaporate if a subject's
reports were re-admitted as evidence because they too
were regarded as forms of behavior.

Historically, therefore, behaviorism was a salutary
corrective that was pushed to inordinate extremes. At
a time when psychology was largely preoccupied with
examining the minutiae of a subject's introspections
there was some point in drawing attention to what
could be publicly observed. But this injunction unfor-
tunately was not accompanied by any suggestion of
new hypotheses that might be tested. It functioned
mainly as a new recipe for continuing the old associa-
tionist program. The widespread implementation of
this recipe, however, had very important consequences
for psychology generally. It enhanced the status of
psychology as a science amongst the scientific commu-
nity. Psychologists could now wear lab-coats like biol-


ogists and be admitted to the Faculty of Science.
Although behaviorism was basically a philosophical
movement psychologists were now able to part com-
pany with philosophers and set up on their own.

Whether this separation has been beneficial in ad-
vancing our understanding of human behavior is an-
other question; for the basic problem in the central
spheres of action, motivation and emotion, perception,
learning, remembering, etc., is to decide what is a
psychological question. In the sphere of learning, for
instance, in which behaviorists evinced most interest,
how much depends upon the conceptual and logical
relationships involved in what has to be learnt and how
much depends on general empirical conditions about
which psychologists might reasonably test hypotheses?
The work of theorists such as Jerome Bruner and Jean
Piaget, who have been concerned with human learning
and development in a concrete rather than a program-
matic way, raises such problems in an acute form. But
it is difficult to see how much progress can be made
until issues of this sort are squarely faced. But to face
them would involve a revolution in psychology as
radical as the methodological movement which Watson
himself initiated.


This bibliography includes works referred to in the text
as well as important works of reference.

D. M. Armstrong, A Materialist Theory of Mind (London
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of B. F. Skinner, Verbal Behavior, Language, 35 (1959),
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(New York, 1946). D. W. Hamlyn, “Behaviour,” Philosophy,
28 (1953), 132-45; idem, “Causality and Human Behav-
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(1964), 125-42. E. R. Hilgard, Theories of Learning, 2nd ed.
(New York, 1956). T. Hobbes, De corpore, Works, Vol. I,
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(New York, 1943). K. S. Lashley, “The Behaviorist Inter-
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Philosophy of Science,
7 (1957), 30-44. R. S. Peters, The
Concept of Motivation
(London and New York, 1958; reprint
New York, 1965); idem, ed., Brett's History of Psychology,
rev. ed. (London and New York, 1962); idem, “Emotions,
Passivity and the Place of Freud's Theory in Psychology,”
in B. B. Wolman and E. Nagel, Scientific Psychology (New
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(New York, 1953); idem, Verbal Behavior (New
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J. J. C. Smart, Philosophy and Scientific Realism (London and
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(London, 1964). E. B. Titchener, Lectures on the Elementary
Psychology of Feeling and Attention
(New York, 1908). E. C.
Tolman, Purposive Behavior in Animals and Man (New
York, 1932). J. B. Watson, Psychology from the Standpoint
of the Behaviorist
(Philadelphia, 1919); idem, Behaviorism
(New York, 1924; Chicago, 1958; also reprint). B. B.
Wolman, Contemporary Theories and Systems in Psychology
(New York, 1960). R. S. Woodworth, Contemporary Schools
of Psychology
(New York, 1931; 1943).


[See also Baconianism; Education; Historical and Dialecti-
cal Materialism; Idea; Man-Machine; Pragmatism;