A Differential Outcomes Effect Using Biologically Neutral Outcomes in

Delayed Matching-to-Sample with Pigeons

Ronald Kelly and Douglas S. Grant

University of Alberta

The differential outcomes effect (DOE) pertains to enhanced conditional discrimination performance if each correct stimulusÕ choice sequence is always followed by a different outcome (e.g., food vs. water), compared to if each correct sequence is equally often followed by either outcome. The present experiments sought evidence of a DOE in pigeons, using biologically neutral outcomes. Experiment 1 replicated findings with rats demonstrating that a DOE can occur when one outcome is a biologically neutral light and the other is the absence of that light. Experiment 2 extended these findings by demonstrating a DOE when two biologically neutral outcomes of similar sensory and associative properties were employed.