Drive, Reinforcement, and Learning

The concept of drives is very important to the theories of Clark L. Hull, a
neobehaviorist. According to Hull, a drive has at least two distinct functions
as far as behavioral activation is concerned. Without drives there could be
no reinforcement and thus no learning, because drive reduction is the reinforcement.
Without drives there could be no responses, for drives activate
behavioral potentials into performance. Drive theory maintains that a state
named “drive” (or D) is a necessary condition for behavior to occur; however,
D is not the same as the bodily need. D determines how strongly and
persistently a behavior will occur; it connects the need and behavior. This
distinction between need and drive is necessary because, while the state of
need serves as the source of behavior, the intensity of behavior is not always
related to the intensity of need. Need can be defined as a state of an organism
attributable to deprivation of a biological or psychological requirement,
related to a disturbance in the homeostatic state.
There are cases in which the need increases but behavior does not, or in
which the need remains but behavior is no longer manifested. Prolonged
deprivation, for example, may not result in a linear or proportional increase
in behavior. A water-deprived animal may stop drinking even before cellular
dehydration is restored to the normal state; the behavior is changing independently
of homeostatic imbalance. Cessation of behavior is seen as being
attributable to drive reduction.
Hull uses D to symbolize drive and sHr (H is commonly used to denote
this, for convenience) to symbolize a habit which consists of an acquired relationship
between stimulus (S) and response (R). It represents a memory
of experience in which certain environmental stimuli and responses were
followed by a reward. An effective reward establishes an S-R relationship; the
effect is termed reinforcement. One example of an H would be an experience
of maze stimuli and running that led to food. H is a behavioral potential,
not a behavior. Food deprivation induces a need state that can be physiologically
defined; then D will energizeHinto behavior. The need increases
monotonically with hours of deprivation, but D increases only up to three days without food. A simplified version of the Hullian formula for a behavior
would be “behavior = HD,” or “performance = behavioral potential energizer.”
The formula indicates that learning, via establishing behavioral potential,
and D, via energizing the potential, are both necessary for performance
to occur. This is a multiplicative relationship; that is, when either H
or D is zero, a specific performance cannot occur.