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Dictionary of the History of Ideas

Studies of Selected Pivotal Ideas
  
  
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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


225

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
need-reduction.

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.