Short-Term Retention in Delayed Simple and Conditional Discriminations with Pigeons

Douglas S. Grant and Ronald Kelly

University of Alberta

Pigeons were trained in delayed simple (DSD) and conditional (DCD) discriminations in which all trials ended in food. Pecking the test stimulus was reinforced on go trials, and not pecking the test stimulus was reinforced on no-go trials. In a DSD, the initial stimulus determines whether the trial is go or no-go, whereas in a DCD, the combination of initial and test stimulus determines whether the trial is go or no-go. Hence, a DSD, but not a DCD, can be mediated by a simple response intention (i.e., peck or do not peck). Rate of forgetting in the DSD and DCD was equivalent, regardless of whether (a) the initial stimuli were colors or lines and (b) the DSD involved 1 or 9 different test stimuli. It was concluded that simple response intentions do not mediate retention in a DSD. The data further suggest that in DSDs and DCDs in which both initial and test stimuli are differentiated visually, pigeons encode and remember the initial stimuli (i.e., code retrospectively).