Punished avoidance behavior in the presence of a non-punished alternative

Following the achievement of a bar press avoidance criterion, three marmoset monkeys were exposed to gradually increasing intensities of response shock. After response rates stabilized, a non-punished avoidance bar was introduced. No evidence of a response shift occurred through 19 sessions (1900 trials), although two Ss made occasional unpunished avoidance responses, and the third S suddenly shifted to the unpunished bar in the 20th session. Thus, punished avoidance behavior was maintained over a relatively long time despite the non-punished alternative. The final differences were explained in terms of reinforcing and aversive interactions.