TIMING IN PIGEONS - THE CHOOSE-SHORT EFFECT MAY RESULT FROM PIGEONS CONFUSION BETWEEN DELAY AND INTERTRIAL INTERVALS

In conditional discriminations, when samples differ only in duration, pigeons typically show a choose-short effect (i.e., higher matching ac curacy on short-duration-sample than on long-duration-sample trials wi th increasing delay between sample and comparison stimuli). That this effect depends on the similarity of retention interval (RI) and intert rial interval (ITI) houselight illumination conditions has been taken as evidence that pigeons judge duration relative to a temporal backgro und. In the present experiment, pigeons trained with duration samples and with the In either illuminated or not showed a choose-short bias o nly when the RI illumination on test trials was the same as the ITI il lumination had been in training. The results support the hypothesis th at the choose-short effect results from the pigeons' confusion between the ITI and the RI.