Effects of Differential Reward Magnitudes on Simple Brightness Discrimination with Free and Forced Trials

Abstract

Six groups of 10 hooded rats were rewarded to both of two brightness discriminanda. Differential reward was associated with one discriminanda by delivery of 2-1, 6-3, 12-6, 3-1, 6-2, or 9-3 food pellets to the respective groups for 156 trials, 2 choice and 4 forced daily. In a second experiment, 16 of 60 Ss from Exp. 1 received 84 further trials to 6 or 1 pellets. In Exp. 1, one of 6 groups (2-1) showed differential choice of the larger reward while all groups showed strong position habits. On instrumental (forced) trials all groups ran significantly faster to their larger reward. In Exp. 2, Ss previously showing no preference for their larger reward tended toward such a preference, while Ss that had heretofore shown differential choice behavior and no differential speed did develop a significant speed differential.