The effects of ITI fillers in autoshaping

Abstract

The present experiments used pigeons in an autoshaping procedure to examine the effects of a nonreinforced, nontarget stimulus presented during the intertrial interval on responding to a target CS. Experiments 1 and 2 found that a filler stimulus presented during a substantial portion of the ITI retarded responding to the target CS relative to a group not exposed to the filler. This group difference in performance was subsequently abolished by continued training and omitting the filler in the former group (Experiment 1) or adding a filler for the latter group (Experiment 2). Experiment 3 found that when the “filler” occupied most of the interreinforcement interval, CS-US pairings embedded within the “filler” stimulus yielded superior autoshaping relative to a group that received CS-US pairings embedded in static apparatus cues in the absence of the filler. The results are discussed with reference to the ways that a nontarget stimulus during the ITI can influence contextual modulation of responding to a discrete CS and the necessity for comparator theories to incorporate a “local context” view of cycle time to explain the present findings.