Punishment contras during free-operant avoidance.

Punishment of bar-pressing responses of rhesus monkeys with electric shock in one component of a multiple free-operant avoidance schedule suppressed responding in that component. These decreases were concomitant with response rate increases in the unpunished component (punishment contrast). Response rates in both components increased when punishment was removed and decreased in successive sessions. These effects of punishment on unpunished responding were similar to those obtained during single and multiple schedules of positive reinforcement and they suggest a further similarity in the development of discriminations during positive and negative reinforcement schedules.