PIGEONS' WAIT‐TIME RESPONSES TO TRANSITIONS IN INTERFOOD‐INTERVAL DURATION: ANOTHER LOOK AT CYCLIC SCHEDULE PERFORMANCE

Abstract

Recent developments reveal that animals can rapidly learn about intervals of time. We studied the nature of this fast‐acting process in two experiments. In Experiment 1 pigeons were exposed to a modified fixed‐time schedule, in which the time between food rewards (interfood interval) changed at an unpredictable point in each session, either decreasing from 15 to 5 s (step‐down) or increasing from 15 to 45 s (step‐up). The birds were able to track under both conditions by producing postreinforcement wait times proportional to the preceding interfood‐interval duration. However, the time course of responding differed: Tracking was apparently more gradual in the step‐up condition. Experiment 2 studied the effect of having both kinds of transitions within the same session by exposing pigeons to a repeating (cyclic) sequence of the interfood‐interval values used in Experiment 1. Pigeons detected changes in the input sequence of interfood intervals, but only for a few sessions—discrimination worsened with further training. The dynamic effects we observed do not support a linear waiting process of time discrimination, but instead point to a timing mechanism based on the frequency and recency of prior interfood intervals and not the preceding interfood interval alone.