Transitions from Rich-to-Lean Schedules Increase Attack in a Laboratory Model of Social Aggression in Pigeons: I. Fixed-Ratio Schedules

Abstract

Two pigeons key pecked under a two-component multiple fixed-ratio (FR) FR schedule. Each component provided a different reinforcer magnitude (small or large) thatwhich was signaled by the color of the key light.  Large- (rich) and small- (lean) reinforcer components randomly alternated to produce four different types of transitions between the size of the immediately preceding reinforcer and the size of the upcoming reinforcer: lean-to-lean, lean-to-rich, rich-to-lean, and rich-to-rich. During probe sessions, a mirror (which was covered during baseline sessions) was uncovered and attack responses toward the mirror were measured, along with the force of individual mirror attacks. The pigeons paused the longest, and attacked most frequently during the rich-to-lean transitions. The pigeons also exhibited some attacksh during lean-to-lean transitions, and pauses were longer during these transitions than during the lean-to-rich and rich-to-rich transitions.  Pauses were short and attack infrequent during these last two transition types.  In addition, attacks were more forceful during the rich-to-lean transitions thaen during the other transition types.  These data are consistent with the view that rich-to-lean transitions function aversively and, as such, generate behavior patterns, including aggression, commonly produced by other aversive stimuli.