Effects of diazepam and chlorpromazine on socially induced anxiety in pigeons.

The effects of diazepam and chlorpromazine on response suppression in a social situation were studied in pigeons. Three groups of pigeons were trained to peck a key on a variable-interval 60-s schedule of reinforcement, then exposed to the pain reaction of adjoining pigeon to electric shock. Although every pigeon showed suppression of response, the suppression decreased with repeated exposures. A conditioning group received the electric shock with the exposure to the pain reaction of adjoining bird; a shock exposure group received the electric shock without any explicit conditioned stimulus; and a control group did not receive any shock. After these treatments every group was exposed to the pain reaction of the adjoining bird. The conditioning group and the shock exposure group showed clear response suppression, but the control group did not. Although chlorpromazine generally reduced response rate in all groups, diazepam selectively abolished the response suppression.