Portland State University. Department of Psychology
Date of Award
Master of Science (M.S.) in Psychology
1 online resource (24 leaves : ill. ; 28 cm.)
Four types of schedule interactions have been defined: positive contrast, negative contrast, positive induction, and negative induction. Most work has centered on the necessary conditions for positive contrast. One position states that a reduction in reinforcement frequency is necessary; the other view states that a reduction in response rate is necessary. Neither view can account for the occurrence of induction. The present experiment tests the hypothesis that stimulus control effects the occurrence of either contrast or induction. Three pigeons were trained to respond for primary reinforcement (strong stimulus control condition), and three pigeons were trained to respond for conditioned reinforcement (weak stimulus control condition). A response rate decrease was caused by changing the schedule of reinforcement from MULT EXT, VI 1-min, EXT, VI 1-min to MULT VI 1-min, VI 1-min, VI 1-min, VI 1-min for primary reinforcement birds, and to MULT (Chain VI 1-min, VI 1-min), (CHAIN VI 1-min, VI 1-min for conditioned reinforcement birds. Negative contract was observed for all birds receiving primary reinforcement, but positive induction occurred for two of three birds receiving conditioned reinforcement. In the next phase a response rate decrease was caused by changing the schedule to MULT VI 1-min, VI 1-min, DRO 20-sec, VI 1-min for primary reinforcement birds , and to MULT (CHAIN VI 1-min), VI 1-min, CHAIN DRO 20-sec , VI 1-min) for conditioned reinforcement birds. Two of the primary reinforcement birds showed positive contrast, while the third showed negative induction. Two of the conditioned reinforcement birds showed negative induction, while the third showed no effect. Gradients of stimulus control showed no difference between the groups due to the prolonged training before testing for stimulus control. It was concluded that differential amounts of stimulus control can account for the differences in the schedule interactions in this experiment and those observed in previous research.
Homer, Andrew Louis, "Schedule interactions and stimulus control" (1971). Dissertations and Theses. Paper 1427.