Short-term retention in delayed simple and conditional discriminations with pigeons

Pigeons were trained in delayed simple (DSD) and conditional (DCD) discrimi nations in which all trials ended in food. Pecking the test stimulus was re inforced on go trials, and not pecking the test stimulus was reinforced on no-go trials. In a DSD, the initial stimulus determines whether tho trial i s go or no-go, whereas in a DCD, the combination of initial and test stimul i 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 wheth er (a) the initial stimuli were colors or lines and (b) the DSD involved on e or nine different test stimuli. It was concluded that simple response int entions 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 vi sually, pigeons encode and remember the initial stimuli (i.e., code retrosp ectively). (C) 2000 Academic Press.