Tested in 3 experiments the hypothesis that amobarbital attenuates the effects of frustrative nonreward. It was found that the drug blocked the partial reinforcement acquisition and extinction effects. However, it did not alter the frustration effect in the Amsel double runway. The difference between these 2 results was shown in the final experiment not to reflect a difference between conditioned and unconditioned frustration: amobarbital retarded extinction whether this was measured by speed of entry into a frustrating situation or speed of departure from it. (27 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)