Stimulus Control of Operant Behavior

Discrimination

Generalization

Generalization Gradients

Peak Shift

Concepts

Overview of stimulus control of operant behavior

I. Operant Discrimination

Known as the study of discrimination learning or stimulus control

Discriminative stimulus - Signals that reinforcement will be forthcoming if the response occurs (S+ or Sd)

Signals that reinforcement will not be available, even if the response occurs (S)

Discrimination

Animals learn to demonstrate differential patterns to responding to different stimulus conditions

Response Pattern

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S+

S-

Resp/Min

II. Generalization

Similar patterns of responding to similar stimulus conditions

The opposing qualities of discrimination

III. Generalization Gradients

CS+Early in discrimination training

Generalization Gradients

CS+Later in discrimination training

Generalization Gradients

CS+

Excitatory Pattern of Responding

Generalization Gradients

CS-

Inhibitory Pattern of Responding

% CR

Generalization Gradients

CS+ Excitatory of Responding

% CR to tone

1 KHz

Generalization Gradients

CS-

Inhibitory Pattern of Responding

% CR to tone

570 nm

Predictiveness and Redundancy

Conditioning will occur to the stimulus which most predictive

An especially salient CS may overshadow the other stimuli

Overshadowing

Depends upon nature of the environment, the past history of the animal and similar issues

Highly salient stimulus qualities often overshadow other stimuli

Specific features of the stimulus may be attended to

Attention Training

Relevance must be learned Behavior must be demonstrated Transfer of training studies

– Paying attention is a separate part of the discrimination learning

Attention Training

Dimensional shift learning paradigm– Intradimensional shift - Train to CS+

quality, shift to different type of same dimension (e.g. shift from red to blue for CS+)

– Extradimensional shift - Train to CS+ quality, shift to different dimension (e.g. from color to shape for CS+)

Attention Training

Extradimensional shift is more difficult

IV. Process of Generalization

Extinction builds to CS+ and inhibition builds to CS-

Early work of Spence 1936, 1937; and Hull 1943, 1952

According to Spence’s theory, excitation and inhibition add together in an algebraic fashion

Peak Shift Phenomenon

CS+

CS-

Response Strength

Peak Shift Phenomenon

CS+

CS-

Response Strength

V. Natural Concepts

Concepts are related by unifying or common properties

Abstract concepts– “Same” or “different”– Often not limited to specific concrete

qualities

V. Natural Concepts

Some processes– Matching to sample

R

Peck

GR

Reinforce

V. Natural Concepts

Some processes– Oddity responding

R

Peck

GR

Reinforce

V. Natural Concepts

Wittgenstein in 1953 It is not clear what specific features or

qualities are being responded to What is a dog? What are the qualities of “dogginess?”

V. Natural Concepts

Herrnstein work in the 1980s Demonstrated discrimination of natural

objects by pigeons Sort stimuli by water, trees or a particular

person Organisms as simple as pigeons can

reliably demonstrate this discrimination

Learning Theory and Memory

Are there behavioral ways to describe remembering and knowing?

Some procedures include delayed matching to sample– Matching accuracy decreases as a function

of time

Matching Accuracy Over Time

PercentageCorrect

Seconds

100

50

Matching Accuracy Over Time and Sample Duration

PercentageCorrect

Seconds

100

50

14 sec sample

8 sec sample

4 sec sample

Working Memory

Memory is an active process– Susceptible to interference

Retroactive interference - interfering stimulus comes after the stimulus to be remembered

Proactive interference - interfering stimulus comes before the stimulus to be remembered

Working Memory

Symbolic matching works as effectively as direct stimulus matching– For example, red to vertical lines is

remembered as well as red to red– Directed forgetting - stimulus learning is

followed by a signal that the stimulus is to be remembered or not

– It appears memory is an active process

Spatial Memory and Cognitive Maps

Memory for places– Maze learning studies– Little indication of decay over time– Tends to be accounted for by a cognitive

representation of space