Hull’ theory of learning

C.L.Hull (1884-1952) who was professor of psychology at Yale University synthesized into a unified system many of the achievements of his predecessors and built a new system on their strength and avoided some of their pitfalls. His system of behavior studied under S-R reinforcement theorists is deductive, mathematical and testable. Its important features are:
  1. It is based on the association theory of stimulus –response.
  2. It is based in survival model of life.
  3. It is based on biological needs and their fulfillment.
With a view to understand Hull’s theory of learning, following concepts may be explained.
(a)    Need: Need is a state of the organism in which a deviation of the organism, from the optimum of biological conditions necessary for survival, takes place. When a need arises, the organism acts in order to reduce the need. Therefore, Hull’s theory of learning is called need- reduction theory.
Need would produce the behavior and the particular behavior that reduces the need would be gradually learned.
(b)   Drive: It is a common denominator for all primary motivations whether due to food, water, sex or any other cause.
(c)    Reinforcement: Hull explained reinforcement as “ Whenever a reaction (R) takes place in temporal contiguity within afferent receptor impulse (s) resulting from the impact upon a receptor of stimulus energy (S) and this conjunction is followed closely by the diminution in a need, in the tendency if that stimulus on subsequent occasions to evoke that reactions.”
(d)   Unlearned Behavior: Hull recognized the importance of unlearned stimulus-response associations. Unlearned associations are found more frequently on the lower phylogenetic levels than on the higher. Learning’s super-structure is built upon these inherited associations. The nature of inherited response patterns was formulated on the basis of association- doctrine. Hull developed an elaborate symbolism for his theory. The symbol SUR stands for the unlearned stimulus-response association. U is an abbreviation of unlearned. The S and R represent the stimulus and response components of learning respectively.
(e)    The Stimulus: The theories of the behaviorists measure the objective physical stimulus, usually relate to the internal neural activities to a response. For Hull, response are conditioned to the neural after effects of stimuli rather than to the stimuli themselves. The effective stimulus, in learning, is the trace in the nervous system caused by the environmental objects. According to Hull, the stimuli in the object would give rise to stimulus traces in the organism. The first may be designated S and the seconds s. Learning involves S and not the s.
(f)      The Response: A distinction may be made between tendency within the person to make a response and the actual response itself. If we designate the overt response R, we can refer to the pre-existing neural activities which initiate the response as r. These internal response tendencies are not observable but inferred from behavior. Symbolically the learned association, of S and R is represented as SHR. H represents habit. Changes in SHR constitute learning in Hull’s system.
(g)    Learning and Biological Needs: There is a difference between learning and performance. Several factors can influence performance but learning itself as influenced only by one factor, the number of times, the particular response occurring together (contiguity) has been followed by reinforcement.
(h)    Reinforcement: According to Hull all behavior has its origin in the biological needs which are most demanding early in human life. The complex human behavior is based on these biological needs. Reinforcement according to Hull is like Thorndike’s rewarded in one way. It is stimulus which has the ability to alter the probabilities of certain R following certain S.When a response is reinforced; this implies that it has been followed by one of a certain class of stimuli. Hull envisaged that reinforcing stimuli were those which reduced stimuli uniquely associated with the biological drives.
Hull’s theory of learning is based on the premises that association between S-R is not adequate for learning. Hull holds that some kind of reward or other reinforcement is necessary in order to establish the stimulus as signal. Hull’s theory of learning is the reinforcement theory of learning. He stated his theory in the form of 16 general rules of postulates.

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