Attentuation of the differential outcomes effect by extraneous reward

The reinforcement context model for performance in delayed matching to sample tasks (White and Brown, 2014) predicts the course of forgetting based on the assumption that rewards for extraneous behavior compete with rewards for accurate matching and increase as a linear function of retention-interval duration. In the differential outcomes effect, greater matching accuracy occurs when correct choices produce different outcomes, which the model assumes have greater reward effectiveness than same outcomes. The model was tested in the present experiment with pigeons by arranging an additional task during the retention interval of a delayed matching to sample task, center-key pecking rewarded by food delivered at variable intervals. This additional source of extraneous reward resulted in attenuation of the differential outcomes effect as predicted by the model. The model was supported by satisfactory quantitative fits to the forgetting functions for same and different outcome conditions with and without additional extraneous reward.