1. PSY402 Theories of Learning
Friday
February 21, 2003

2. Discrimination Learning
Important to recognize when reinforcement is not available so that responding can be withheld.
Discriminative stimulus:
SD – reinforcement is available (S+)
SD – reinforcement is unavailable (S-)
Conditioned stimuli always produce a response. Discriminative stimuli signal the opportunity to respond.

3. Two-Choice Discrimination Tasks
The discriminative stimuli are on the same dimension:
Red vs green light.
Need not be presented simultaneously.
Two-choice discrimination includes one SD and one SD .
Other tasks can use multiple multiple SD or multiple SD.

4. Three Phases
Subjects begin by responding equally to both stimuli – prediscrimination phase.
Discrimination phase -- with training, response to SD increases and response to SD declines.
Shift back to non-differential reinforcement to show that behavior was caused by reinforcement.

5. Conditional Discrimination
Availability of reinforcement depends on the condition of a stimulus.
The stimulus does not always signal the same thing.
More difficult to learn.
Nissen’s chimpanzees:
Large, small squares, white or black.
SD = large white, small black.

6. Behavioral Contrast
Behavioral contrast – the increased responding to the differential stimulus, decreased response to SD
Contrast also occurs with changes in the duration of reinforcement.
VI-10 to VI-3
Local contrast – emotional
Sustained contrast – related to the differential reinforcement.

7. Anticipatory Contrast
Williams – sustained contrast occurs due to anticipation of a future reinforcement contingency.
Not due to recall of past contingency.
VI-3, VI-6, VI-3
Compare the first and third VI-3 behavior.
VI-6 affected the first VI-3 more than the last VI-3 -- a prospective effect.

8. Occasion Setting
A conditioned stimulus (CS) can create the conditions for operant responding to a second conditioned stimulus (CS).
Occasion setting – ability of one stimulus to enhance the response to another stimulus.
The facilitating stimulus does not produce a CR by itself.

9. SD as an Occasion Setter
A Pavlovian occasion-setter can increase operant responding.
Example:
A meal elicits CR craving for cigarette.
Requesting a cigarette after a meal – an operant behavior caused by CR.
Conditional occasion-setting:
Second stimulus modifies meaning of first discriminative stimulus.

10. Conclusions An occasion-setter can increase operant responding.
A discriminative stimulus (SD) can increase response to a CR (Pavlovian conditioning).
This implies interchangeability of Pavlovian occasion-setters and discriminative stimuli.

11. Central Motivational States
Conditioned stimuli influence operant behavior through their effect on motivational states:
Appetitive
Aversive
Emotional responses influence operant behavior.