Incentive Effects and Competing Response Models

Abstract

One or 10 pellets of food in the goal box provided two levels of incentive and a 1- or 4-in. gap, adjacent to the start box, defined two degrees of antagonistic instrumental responses to the approach down a runway. Three groups of hungry rats, (1L-3S), (2L-2S), and (3L-1S), differed in the ratio of large- to small-gap trials throughout 124 days of training at 1 trial per day. The major findings were no G × I interaction for response speed in any ratio group, strong incentive effects in all groups, and a near zero gap effect in Group (3L-1S) despite significant gap effects in the other two groups. The hypothesis that incentive value affects the approach response but not the competing responses elicited by the gap was supported. The differential gap results in the three ratio groups were interpreted as arising from adaptation effects occurring over trials.