Clark Leonard Hull (1884-1952)

1. Clark Leonard Hull (1884-1952) A Cognitive Behavior Theory (and yes, we are skipping over Skinner! Leaving the best for last!)

2. Clark Hull • U of Wisconsin grad: PhD in 1918; most of career at Yale • Three separate parts of career: • Testing of aptitudes: Aptitude Testing (1928) • Hypnosis: Hypnosis and Suggestibility (1933) • Study of learning processes: Principles of Behavior (1943) • Most important of work • Revolutionized study of learning with methodology and modeling • 40% of all experiments in JEP and J of Comparative/physio psych from 1941 to 1950 referenced his theory • Most often sited experimental psychologist until mid 1950s • Interesting fact: had childhood polio and was quite disabled much of adult life

3. Hull’s approach to theorizing • Major influences: • Darwin and concept of adaptive behavior • How do organisms adapt to environment and what factors are involved • Used Hypothetical Deductive or logical deductive approach: • Develops a set of postulates or principles • Deduce from these a set of inferences or theorems using strict logic • Theorems/postulates often involve hypothetical constructs invented by theorists to describe relationships between experimental manipulations and the data • Evaluate the theory by translating deductions from theory into experimental operations and see if data support

4. Hypothetical deductive? • Why use hypothetical deductive approach? • Creates dynamic, open ended system • Constantly generating hypotheses • Constantly evaluating hypotheses with experiments • If data support: strengthens theory • If data not support: revise the theory • Remember: theory merely a tool that aids researcher in synthesizing facts/organizing methods of looking at data • Ultimate test = your data!

5. Major Theoretical Concepts • Based on logically structured set of postulates and theorems • Based on Euclid's geometry • Postulates = general statements about behavior that cannot be directly verified • Theorems that logically flow from postulates CAN be tested

6. The 16 postulates (yes, 16!) • Postulate I: Sensing the External Environment and Stimulus Trace • External stimulation triggers an afferent neural impulse • This impulse outlasts the environmental stimulation • This “left over” neural impulse = stimulus trade (s) • It is this neural impulse that becomes associated with environmental event • Also: neural motor reaction (r) that results in overt response (R) • Thus: S-R becomes S-s-r-R • (Actually is now evidence neurologically to support this!)

7. The 16 postulates • Postulate 2: Interaction of Sensory Impulses • Interaction of sensory impulses ( s ) indicates complexity of stimulation • This complexity demonstrates the difficult of predicting behavior • Behavior rarely function of only 1 stimulus (novel idea at that point) • Important concept: stimuli interact with one another • Related traces interact with one another • Synthesis of these interactions determines behavior • Can draw this function: S1s1 S1s1 S1s1 srR S1s1 S1s1

8. The 16 postulates • Postulate 3: Unlearned behavior • Organism has an innate hierarchy of responses: • Unlearned behavior • Triggered when a need arises • Needs = physiological • Hunger, thirst, aggression, temperature control • Motivated behavior • Hierarchy because more than one response/reaction may occur to a need • If first response does not reduce need, then second response elicited, and so on • If innate responses do not resolve need, this creates need for learning • Learning only required when innate responses do not resolve a need

9. The 16 postulates • Postulate 4: Contiguity and Drive Reduction as necessary condition for learning • If S leads to R, and IF R results in satisfaction of biological need, the association between S and R is strengthened • More often the S-R association occurs, the stronger the relation and the stronger the R is to the S (Basically restates Thorndike’s law of exercise) • Primary Reinforcement MUST involve need satisfaction or drive reduction

10. The 16 postulates • Postulate 4 also addresses secondary reinforcers: • Reinforcer = S that has been closely and consistently associated with diminution of a need” • Secondary reinforcer following a response also increases with S2-R pairings • If a S is followed by an R, which in turn is followed by a reinforcer, the association between the S and R is strengthened • Habit strength: SHR • Note that is very specific: a reinforcer MUST reduce a drive • One of most important concepts: refers to strength of association between S and R • Can mathematically model: • SHR =1-10-0.0305N • N= # of pairings between S and R • Formulates negatively accelerated learning curve

11. The 16 postulates • Postulate 5: Stimulus Generalization • Ability of new S’s to elicit conditioned R is determined by similarity to the original S+ used during training • SHR will generalize from 1 S to another to extent that 2 S’s are similar • Prior experience also matters: • Learning that takes place under similar conditions will transfer to new learning situation • Generalized Habit Strength: SHR • Identical to Thorndike here

12. The 16 postulates • Postulate 6: Stimuli associated with Drives • Biological deficiency in organism produces a drive (D) • Each drive associated with specific stimuli • E.g., hunger = stomach growling; thirst = dry lips, etc. • Existence of specific drive S makes it possible to teach animals to behave differently for different drive states • Can respond one way to hunger stimuli; another to thirst stimuli • Drive states can be elicited by different stimuli

13. The 16 postulates • Postulate 7: Reaction potential as function of Drive and Habit Strength • Likelihood of learned response emitted at any point in time = reaction potential or SER • SER = f(SHR x D) • SHR must be activated by D • Drive does not direct behavior, just arouses it • D is motivator: arouses and intensifies R • Without D, animal cannot engage in learned response even with strong association • Must be a motivator, so to speak • Is a motivator in that engages behavior • Thus: reaction potential = SER = f(SHR x D) • If SER or SHR = 0, then reaction potential must be 0 • Reaction potential also related to resistance to extinction, latency and amplitude of response

14. The 16 postulates • Postulate8: Responding causes Fatigue, which operates against the elicitation of a conditioned response • Responding requires work; work results in fatigue • Fatigue eventually inhibits responding • Reactive inhibition (IR): • Caused by fatigue associated with muscular activity • Related to amount of work involved in response • Automatically dissipates when organism stops performing • Used to explain spontaneous recovery: • no longer fatigued! • After rest, IR dissipates, animal begins to respond again • Extinction also influenced by IR

15. The 16 postulates • Reminiscence effect: • Improvement of performance after a break • Explained by assuming that IR builds up during training; operates against tracking performance • After rest, IR dissipates, performance improves • Evidence? • Data from massed vs. distributive practice • Distributive practice = better performance/learning • Modern theorists disagree with “how” but reminiscence effect is strong and needs to be dealt with…..

16. The 16 postulates • Postulate 9: Learned response of NOT responding • Fatigue = negative drive state • Thus: not responding = reinforcing • Allows IR to dissipate • SIR = conditioned inhibition: • Learn not to respond (reinforcer is decrease in fatigue) • Note that IR and SIR work against each other • Subtracted from reaction potential: Effective reaction potential • Thus: effective reaction potential = SER=SHR X D – (IR + SIR)

17. The 16 postulates • Postulate 10: factors tending to inhibit a learned response change from moment to moment • Inhibitory potential = oscillation effect: SOR • Varies from moment to moment within limited range • Values are normally distributed: • middle values most likely to occur • Explains why learned behavior may not occur in given instance • Operates against elicitation of learned response • His fudge factor • Can now quantify: Momentary Effective Reaction Potential = . SER=[SHR X D – (IR + SIR)]- SOR

18. The 16 postulates • Postulate 11: momentary effective reaction must exceed a certain value before a learned response can occur . • Reaction threshold = SLR = the value that SER must exceed for conditioned R to occur . • Learned response will only occur if SER > SLR • Postulate 12: probability that a learned response will be made is combined function of . SER, SOR and SLR • After a few reinforced trials, SER approaches SLR • because effects of SOR on conditioned response elicited on some trials, but not others • On some trials: value of SER-SOR is large enough to reduce SER to value below SLR • As training continues, subtracting SOR from SER has less and less effect (value of SER becomes much larger than value of SLR) • BUT: even after long training, possible for SOR to assume large value, thus preventing conditioned response

19. The 16 postulates . • Postulate 13: The greater the value of SER, the shorter the latency between S and R • Latency(STR) = time between presentation of S to organism and its learned response • Reaction time between onset of S and elicitation of learned R decreases as value of : SER increase . • Postulate 14: The value of SER will determine resistance to extinction . • Value of SER at end of training determines resistance to EXT • EXT = how many non-reinforced responses made before extinction occurs . • The greater the value of SER, the greater the # of non-reinforced trials that must occur before EXT • n = number of non-reinforced trials that occur before EXT . • Postulate 15: Amplitude of conditioned response varies directly with SER • Some learned responses occur in degrees • When conditioned response is one that can occur in degrees, its magnitude will be directly related to size of SER = momentary effective reaction potential • Postulate 16: when 2 or more incompatible responses tend to be elicited in the . same situation, the one with the greater SER will occur.

20. Summary of Terms • D = drive • SHR = habit strength • SER = reaction potential = SHR X D • IR = reactive inhibition • SIR = conditioned inhibition • SER = effective reaction potential = SHR x D-(IR+SIR) • SOR = oscillation effect . • SER = momentary effective reaction potential = SER-SOR= [SHR X D - (IR+SIR)]-SOR • SLR = value that SER must exceed before a learned response can occur • StR = reaction time • p = response probability • n = trials to extinction • A = response amplitude