THE EFFECT OF PUNISHMENT SHOCK INTENSITY UPON RESPONDING UNDER MULTIPLE SCHEDULES¹

Abstract

In the first of two experiments, responses of two pigeons were maintained by multiple variable-interval, variable-ratio schedules of food reinforcement. Concurrent punishment was introduced, which consisted of a brief electric shock after each tenth response. The initial punishment intensities had no lasting effect upon responding. Then, as shock intensity increased, variable-ratio response rates were suppressed more quickly than variable-interval response rates. When shock intensity decreased, variable-interval responding recovered more quickly, but the rates under both schedules eventually returned to their pre-punishment levels. In the second experiment, the following conditions were studied in three additional pigeons: (1) With each shock intensity in effect for a number of sessions, punishment shock intensity was gradually increased and decreased and responding was maintained by multiple variable-ratio, fixed-ratio schedules of food reinforcement; (2) Changes in punishment shock intensity as described above with responding maintained by either a variable-ratio or a fixed-ratio schedule, which were presented on alternate days; (3) Session-to-session changes in shock intensity with responding maintained by multiple variable-ratio, fixed-ratio schedules. Responding under the two schedules was suppressed to approximately the same extent by a particular shock intensity. Also, post-reinforcement pauses under the fixed-ratio schedule increased as response suppression increased.

Bouts of Responding: The Relation Between Bout Rate and the Rate of Variable‐interval Reinforcement

“…For example, when total response rate is increased by increasing the reinforcer rate, the response is strengthened in the sense that its rate is made more resistant to disruption (Nevin & Grace, 2000;Smith, 1974). In contrast, when response rate is increased by adding a ratio (or related) contingency, the response rate is made more ''fragile'' (Catania, 1998, p. 122) in the sense of becoming less resistant to disruption (Lattal, 1989;Nevin, Grace, Holland, & McLean, 2001;Powell, 1970). The analysis of bouts suggests one possible way to understand such apparent inconsistencies.…”

“…The decline in bout-initiation rate due to adding the VR 4 requirement could reflect such a decline in reinforcement. Moreover, a decline in reinforcement due to the VR 4 requirement might help explain why response rates that are increased by ratio contingencies are thereby made more suscep-tible to disruption (Lattal, 1989;Nevin et al, 2001;Powell, 1970).…”

Some Effects of Punishment Shock Intensity Upon Discriminative Responding

“…Responding under the VI schedule was generally more resistant to the suppressive effects of punishment than VR responding. Powell (1970) also observed this effect during multiple VR-VI schedules. This resistance to suppression appears to be related to the very slight decreases in reinforcement frequency that occur as VI responding decreases, while reinforcement frequency changes in direct proportion to changes in response rate under VR schedules.…”

“…It is possible that the third animal would have responded similarly, had a less-intense punishment shock been presented initially. Increased responding at low punishment shock intensities was observed in several animals in another recent experiment (Powell, 1970). In summary, it would appear that aversive stimuli may differentially affect discriminative performance, depending upon the intensity of the stimuli and the manner in which they are scheduled relative to the response.…”

“…Since suppression of responding increases as punishment shock intensity increases, reinforcement frequency would be differentially affected under the two schedules. Under VR schedules, reinforcement frequency decreases in direct relation to decreases in response rate, while suppression of VI responding reduces reinforcement frequency only slightly (Powell, 1970). Thus, any differential changes in reinforcement frequency could be related to changes in discriminative performance, if they occurred.…”