Systematic errors in pigeons’ memory for event duration: Interaction between training and test delay

Abstract

Pigeons trained to choose different stimuli following short- and long-duration signals make disproportionately more “short” choices (i.e., “choose-short errors”) following an increase in the retention interval and more “choose-long errors” following a decrease in this delay. The present experiment provided a systematic investigation of how these selective errors depend on the relationship between the training delay and the test delay. Pigeons were first trained with a 0-sec delay between the signal (2- or 8-sec food presentations) and the choice stimuli (red- and blue-lit keys). On subsequent test trials with 5- and 10-sec delays, choose-short errors predominated. Next, the birds were trained with a constant 10-sec delay and then tested with shorter or longer delays on some trials. The birds now responded accurately and without selective errors at the 10-sec training delay, but made choose-long errors at shorter delays and choose-short errors at longer delays. Finally, the birds were trained with a constant 20-sec delay and then tested with shorter and longer delays. Choose-long errors again appeared at shorter test delays, choose-short errors at longer test delays, and no differential errors at the 20-sec training delay. The selectivity of these errors generally increased with the absolute difference between the training and test delay. Theoretical implications of these results are discussed.