CLARK L' HULL

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CLARK L. HULL

• 1884-1952

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PRINCIPLES OF BEHAVIOUR (1943)

• Hulls first major book on learning radically
  changed the study of learning.
• It was the first attempt to apply comprehensive
  scientific theory to the study of a complex
  psychological phenomenon.

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HULLS APPROACH TO THEORIZING

• His approach to theory construction has been
  called HYPOTHETICAL DEDUCTION (logical
  deductive).
• Theory has a logical structure of postulates and
  theorems.
• Postulates-are general statements about behaviour
  that cannot be directly verified.

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HULLS APPROACH TO THEORIZING

• From the postulates, theorems are generated.
• Theorems are deduced from the postulates.
• Theorems can be tested.

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MAJOR THEORETICAL CONCEPTS (1943)

• POSTULATE 1 Sensing the external environment and
  the stimulus trace.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 2 The interaction of sensory
  impulses.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 3 unlearned behaviour.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 4 Contiguity and drive reduction as
  necessary conditions for learning.

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HABIT STRENGTH

• Refers to the strength of the association between
  a stimulus and a response.
• As the number of reinforced pairings between a
  stimulus and a response goes up, the habit
  strength of that association goes up.

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The relationship between gains in habit strength
and successive reinforcements
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MAJOR THEORETICAL CONCEPTS

• POSTULATE 5 Stimulus generalization.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 6 stimuli associated with drives.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 7 Reaction potential as a function of
  drive and habit strength.

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REACTION POTENTIAL

• Is a function of both HABIT STRENGTH and DRIVE.
• For a learned response to occur, HABIT STRENGTH
  has to be activated by DRIVE.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 8 Responding causes fatigue, which
  operates against the elicitation of a conditioned
  response.

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REACTIVE INHIBITION

• REMINISCENCE EFFECT the improvement of
  performance following the cessation of practice.
• MASSED VERSUS DISTRIBUTED PRACTICE when training
  trials are spaced far apart performance is
  superior compared to massed practice.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 10 FACTORS TENDING TO INHIBIT A
  LEARNED RESPONSE CHANGE FROM MOMENT TO MOMENT.

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OSCILLATION EFFECT

• A factor operating against the elicitation of a
  learned response, whose effect varies from moment
  to moment but always operates within a certain
  range of values.
• The oscillation effect must be subtracted from
  the effective reaction potential which creates
  the MOMENTARY EFFECTIVE REACTION POTENTIAL.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 11 MOMENTARY EFFECTIVE REACTION
  POTENTIAL MUST EXCEED A CERTAIN VALUE BEFORE A
  LEARNED RESPONSE CAN OCCUR.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 11 MOMENTARY EFFECTIVE REACTION
  POTENTIAL MUST EXCEED A CERTAIN VALUE BEFORE A
  LEARNED RESPONSE CAN OCCUR.
• This is called the REACTION THRESHOLD.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 12THE PROBABILITY THAT A LEARNED
  RESPONSE WILL BE MADE IS A COMBINED FUNCTION OF
  THE MOMENTARY EFFECTIVE REACTION POTENTIAL, THE
  OSCILLATION EFFECT, AND THE REACTION THRESHOLD.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 13 THE GREATER THE VALUE OF THE
  MOMENTARY EFFECTIVE REACTION POTENTIAL THE
  SHORTER THE LATENCY WILL BE THE LATENCY BETWEEN S
  AND R.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 14 THE VALUE OF THE MOMENTARY
  EFFECTIVE REACTION POTENTIAL WILL DETERMINE
  RESISTANCE TO EXTINCTION.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 15 THE AMPLITUDE OF A CONDITIONED
  RESPONSE VARIES DIRECTLY WITH THE MOMENTARY
  EFFECTIVE REACTION POTENTIAL.

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MAJOR THEORETICAL CONCEPTS

• POSTULATE 16 WHEN TWO OR MORE INCOMPATIBLE
  RESPONSES TEND TO BE ELICITED IN THE SAME
  SITUATION, THE ONE WITH THE GREATEST MOMENTARY
  EFFECTIVE REACTION POTENTIAL WILL OCCUR.

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MAJOR DIFFERENCES BETWEEN HULLS 1943 AND 1952
THEORIES

• INCENTIVE MOTIVATION (K)
• In 1943, Hull treated the magnitude of
  reinforcement as a learning variable. The greater
  the amount of drive reduction, the greater the
  increase in habit strength.
• However, experiments indicated that performance
  was dramatically altered as the size of
  reinforcement was varied after learning was
  complete.

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CRESPI (1942)
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HULL (1952)

• STIMULUS-INTENSITY DYNAMISM (V)
• An intervening variable that varies along with
  the intensity of the external stimulus (S).
• The greater the intensity of a stimulus, the
  greater the probability that a learned response
  will be elicited.

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CHANGE FROM DRIVE REDUCTION TO DRIVE STIMULUS
REDUCTION

• Hulls original theory was a drive reduction
  theory but he modified this to a drive stimulus
  reduction.
• He concluded that drive reduction was too far
  removed from the presentation of the reinforcer
  to explain how learning could take place.
• Replaced it with DRIVE STIMULI.

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FRACTIONAL ANTEDATING GOAL RESPONSE

• One of Hulls most important concepts.
• related to secondary reinforcement.
• Maze learning example

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FRACTIONAL ANTEDATING GOAL RESPONSE

• It is the conditioned response to stimuli,
  experienced prior to the ingestion of food.
• via classical conditioning processes, stimuli
  prior to those occurring in the goal box to also
  become reinforcers, and then the stimuli before
  them, and so on.

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THE HABIT FAMILY HIERARCHY

• The route that is most likely is one that brings
  the animal into proximity of reinforcement most
  rapidly.
• GOAL GRADIENT HYPOTHESIS.
• Delay of reinforcement has a deleterious effect
  on reaction potential.

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THE HABIT FAMILY HIERARCHY

• The habit family hierarchy refers to the fact
  that in any learning situation, any number of
  responses are possible and the one that is most
  likely is the one that brings about reinforcement
  most rapidly with the least amount of effort.
• If this way is blocked, the animal will prefer
  the next shortest route.

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HULLS FINAL SYSTEM SUMMARIZED

• THERE ARE THREE KINDS OF VARIABLES IN HULLS
  THEORY
• 1. independent variables, which are stimulus
  events systematically manipulated by the
  experimenter.

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HULLS FINAL SYSTEM SUMMARIZED

• 2. Intervening variables, which are processes
  thought to be taking place within the organism
  but are not directly observable.
• 3. Dependent variables, which are some aspect of
  behaviour that is measured by the experimenter in
  order to determine whether the independent
  variables had any effect.

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SUMMARY OF HULLS THEORY OF LEARNING AFTER 1952
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EVALUATION OF HULLS THEORY

• No theory has been more thoroughly scrutinized,
  attacked, and dissembled more than Hulls.

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CONTRIBUTIONS

• One strength was the possibility of falsifying
  its various propositions.
• He was willing to take risks in theory
  construction.
• The drive reduction hypothesis was the first
  attempt to break from the imprecise definitions
  of satisfiers/reinforcers that characterized both
  Thorndikes and Skinners theories.
• He was also the first to make precise predictions
  about joint effects of learning and drive on
  behaviour and about the effects of fatigue
  (reactive and conditioned inhibition).

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CRITICISMS

• Little value in predicting behaviour outside of
  the laboratory.
• Insisting that all concepts of interest be
  operationally defined.
• For making inconsistent predictions.
• Hull did not revise his theory enough in the face
  of problematic data and may have ignored many
  contradictory results.