Effects of a pre-aversive stimulus upon oddity performance in monkeys

Two monkeys (Macaca mulatta) were trained to perform an oddity discrimination using automatically projected patterned stimuli. After criteria for both response and discrimination stability were met, a tone followed by shock was superimposed upon the ongoing behavior. Each 60-sec tone was terminated with the onset of a 0.3-sec, 1 to 1.5-ma electric shock. During the tone, baseline responding was partially suppressed but discrimination performance was little altered from the pre-tone period. When shock was raised to 2 to 3 ma, responding was further suppressed, but discrimination performance was again essentially unaltered.