EXTINCTION‐INDUCED AGGRESSION¹

TLDR

Pigeons were trained to peck a key during alternating periods of food reinforcement and extinction. When food reinforcement ceased, the pigeons attacked nearby pigeons or a stuffed model, with attack duration inversely related to time since last food and directly related to the number of reinforcements; the aggression was triggered by the transition to extinction, not by food sight, competition, or superstition, and was reduced by prior satiation.

Abstract

Pigeons were conditioned to peck a response key under a procedure that alternated periods of food reinforcement with periods of extinction. The pigeons attacked a nearby pigeon at the onset of extinction. Some also attacked a stuffed model of a pigeon. The duration of attack was an inverse function of the time since the last food reinforcement and a direct function of the number of reinforcements. The pigeons attacked after the last food delivery whether or not the conditioned pecking response was required and whether or not the extinction period was signaled. The food had to be eaten; the mere sight and sound of food being delivered did not produce attack. Prior satiation reduced attack. The phenomenon was not attributable to a past history of competition between pigeons since socially deprived pigeons also attacked. Superstitious reinforcement of attack was not found to be a factor. The results indicated that the transition from food reinforcement to extinction was an aversive event that produced aggression.