Perceptual learning in the discrimination of interaural time differences

Abstract

Experiments were conducted to clarify whether spatial resolution improves with practice. Four adult subjects were involved in measuring a discrimination threshold in interaural time difference (ITD) discrimination tasks. The threshold was measured using adaptive, 2-alternative, forced-choice procedure. The subjects were pretested with 500-Hz pure tones which have ±300 (plus meaning that the right channel signal leads) or 0 μs ITDs. Then two subjects were repeatedly tested for 9 days (about 80 min per day) at 300 μs ITD and the others at −300 μs ITD, with feedback to their responses. Following the practice period they were tested at ±300 and 0 μs ITDs again (post-test). At the trained ITDs, the spatial resolution improved throughout practice period, and the threshold declined from 81 to 39 μs on average between pretest and post-test. At untrained ITDs, on the other hand, the resolution did not improve between two tests. The improvement was maintained even 74 days after the post-test. These results suggest that the spatial resolution based on ITD improves with practice, and the improvement occurs locally in a certain ITD region, at least within 300 μs around the trained ITD.