Effects of d-amphetamine on responding simultaneously maintained and punished by presentation of electric shock

Responding of two squirrel monkeys with a previous avoidance history was developed and maintained under a multiple fixed-interval 10-min schedule of food and electric shock presentation. Under this schedule the first response after 10 min produced either food or shock depending on the prevailing stimulus condition. Subsequently, responding maintained by food was suppressed when each 30th response produced shock (punishment). Presentation of the same intensity electric shock (10 mA) under the fixed-interval schedule in the other component continued to maintain high positively-accelerated rates of responding. Although increases in punished responding do not usually occur with d-amphetamine, under these conditions, where responding was both maintained and suppressed by the same consequent event, d-amphetamine markedly increased punished responding. Responding maintained by the presentation of shock was also increased by d-amphetamine. The effect of d-amphetamine on punished responding can depend on specific features of the situation in which behavior is studied.