The Timing of Auditory and Visual Signals by Pigeons: Differential Sensitivity to Intertrial Interval Duration

Abstract

In Experiment 1, pigeons were trained to discriminate short (2-s) and long (8-s) durations of a light to yellow/blue comparisons and the same durations of a tone to red/green comparisons. Following training with a constant intertrial interval (ITI) of 10 s, the ITI was varied within sessions (4, 8, 16, or 32 s). On trials with the light, signal duration alone influenced choice responding. The preceding ITI duration had no effect. On trials with the tone, both the signal duration and the preceding ITI duration affected choice responding. Subsequent delay testing in the context of variable ITIs generally replicated the different response biases previously reported with tone vs light signals. In Experiment 2, signal omission testing resulted in a bias to respond “short” regardless of whether the comparisons associated with light signals or the comparisons associated with tone signals were presented. However, on signal omission trials the preceding ITI duration continued to affect choice responding when comparisons associated with the tone signals were presented, but not when comparisons associated with the light signals were presented. These findings regarding stimulus properties and ITI effects can be explained by the information processing model of timing.