STIMULUS CONTROL OF BEHAVIOR

Chapter 10

Stimulus Control of Behavior Generalization

Responding in the same manner to similar stimuli.

Discrimination LearningResponding in different ways to different

stimuli.

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The Generalization Process

Stimulus generalization/discrimination occurs frequently in the real world

Sometimes it is undesirable Black Americans hold negative stereotypes

of their own group (e.g., racial prejudice). Children over generalize rules of language

(e.g., Christine “goed” to the hockey game) Sometimes it is undesirable

Republican talk show hosts are idiots. It “snowed” today.

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Generalization Gradient

A visual representation of the response strength produced by stimuli of varying degrees of similarity to the training stimulus.

Excitatory generalization gradients A graph showing the level of generalization

from an excitatory conditioned stimulus (S+) to other stimuli.

Trained on S+, and then tested in extinction on S+ and other values.

Many studies of these gradients employ pigeons, which have excellent color vision.

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Gutman and Kalish (1956)

Group 530

Group 550

Group 580

Group 600

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Inhibitory Generalization Gradients

Weisman and Palmer (1969) illustrate the inhibitory-conditioning generalization gradient.Green disk (S+) rewarded with food on a

VI-1 min. schedule.White vertical line (S-) on green disk no

food.Tested with a series of white lines

ranging from 0-90 degrees off the vertical on green disk

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Results from 5 pigeons

Smartest Pigeon

Dumbest Pigeon

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Hull-Spence Theory

According to the Hull-Spence view, discrimination learning develops in 3 stages. First, conditioned excitation develops to the S+

as a result of reinforcement. Second, nonreinforcement in the presence of

the S- results in the development of conditioned inhibition to the S-.

Finally, the excitation and inhibition generalize to other stimuli.

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Predictions

The Hull-Spence model predicts a steeper generalization gradient with discrimination training than with nondiscrimination training.

The maximum response occurs not to the S+, but rather to a stimulus other than the S+, and in the stimulus direction opposite that of the S+.

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The Peak Shift Phenomenon

Hanson (1959) reported responding might be shifted from S+. The greatest response for discrimination-

training subjects was not to the S+ but to a stimulus away from S+ opposite the direction of the S-

His results support Spence-Hull

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Peak shift

The shift in the maximum response, which occurs to a stimulus other than S+ and in the stimulus direction opposite that of the S-

In contrast, pigeons receiving nondiscrimination training responded maximally to the S+

The overall level of response was higher with discrimination training than with nondiscrimination training, which the Hull—Spence model did not predict.

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Is Generalization Passive or Active? Both!

Passive generalization: Perceptual confusion does happens because the stimuli can’t be distinguished.

Active generalization: In other situations, animals or people may generalize to stimuli that are very different to the conditioning stimulus

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Passive Generalization Process

Lashley-Wade theoryAnimal is unable to distinguish between the

generalization test stimulus and the trained stimulus. Thus, failure to discriminate between training

and test stimuli is responsible for stimulus generalization.

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Lashley and Wade Predictions 1. Perceptual experience should influence

the amount of stimulus generalization. 2. Discrimination training results in

generalization only to stimuli very similar to the conditioning stimulus

3. Generalization to stimuli dissimilar to the training stimulus should occur when nondifferential reinforcement training is used.

4. Preexposure to a common element may reduce generalization

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Ducklings raised in mono-light

Monochromatic-Light

Normal-Light

(Evidence for #1)

(Evidence for #2)

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Jenkins and Harrison (1960)

Nondifferential

Differential(Tone, VI, No Tone: EXT

(Tone always “On”)

(Evidence for #3)

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Mackintosh, Kaye, Bennett (1991) Grp Preexposed:

Lemon Drink Grp Novel:

No Lemon Drink

Conditioning Lemon + Salinefollowed by LiCl illness

Test Lemon + Saline Lemon + Sucrose

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Example of Active Generalization

Group 1 Noise No Food Tone Food Click Food

Group 2 Noise No Food Tone No Food Click Food

Testing Click Shock

Generalization Test: Tone (more fear) vs. Noise

Acquired Equivalence: Generalization between physically different stimuli trained alike

Testing Click Shock

Generalization Test: Tone and Noise (equal fear)

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