Procedural Determinants of Coding Processes in Pigeons’ Memory for Duration

Abstract

Pigeon's retention functions for duration samples differ qualitatively in choice and successive delayed-matching-to-sample tasks. This research tested procedures designed to be hybrids of these tasks. In Experiment 1, adding a fixed-interval component to the test phase of the choice procedure did not eliminate the “respond-short” effect that is characteristic of retention functions for duration in the choice task. A respond-short effect was not present after the birds were subsequently trained in the successive task. In Experiment 2, a choice component was added to the successive task by providing an option stimulus that could be selected to obtain reinforcement on S-trials that followed either short or long samples. Pigeons showed a respond-short effect under this successive-option procedure but did not show a respond-short effect after training with the option stimulus removed from the successive procedure. Thus, the different retention functions obtained in choice versus successive tasks do not appear to reflect differences in the temporal aspect of the test stimulus schedule or the successive versus simultaneous viewing of the test stimuli. Instead, a respond-short effect emerges when subjects make a choice response based on sample duration, but not when they make a go/no-go response based on sample duration.