PROCEDURAL DETERMINANTS OF CODING PROCESSES IN PIGEONS MEMORY FOR DURATION

Pigeon's retention functions for duration samples differ qualitatively in choice and successive delayed-matching-to-sample tasks. This resea rch tested procedures designed to be hybrids of these tasks. In Experi ment 1, adding a fixed-interval component to the test phase of the cho ice procedure did not eliminate the ''respond-short'' effect that is c haracteristic of retention functions for duration in the choice task. A respond-short effect was not present after the birds were subsequent ly 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 e ither short or long samples. Pigeons showed a respond-shea effect unde r this successive-option procedure but did not show a respond-short ef fect after training with the option stimulus removed from the successi ve procedure. Thus, the different retention functions obtained in choi ce versus successive tasks do not appear to reflect differences in the temporal aspect of the test stimulus schedule or the successive versu s simultaneous viewing of the test stimuli. Instead, a respond-short e ffect emerges when subjects make a choice response based on sample dur ation, but not when they make a go/no-go response based on sample dura tion. (C) 1996 Academic Press, Inc.