PSY402 Theories of Learning Friday February 21, 2003

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.

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.

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.

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.

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.

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.

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.

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.

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.

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