Auditory learning with binaural cues to localisation

Ellis, W. and Rowan, D. (2006) Auditory learning with binaural cues to localisation. BSA Short Papers Meeting on Experimental Studies of Hearing and Deafness, London, UK. 13 - 14 Sep 2006.

Abstract

The performance of normal–hearing humans on various auditory discrimination tasks improves with multi–hour practice/training; that is ‘learning’ takes place. However, few studies have investigated this learning for binaural cues over earphones. On the basis of an initial experiment, Wright & Fitzgerald (2001) argued that low–frequency ITD discrimination is not influenced by multi–hour training in general whereas high–frequency ILD discrimination is influenced by multi–hour training. They suggested that the implied difference in time–course between cues may be related to known differences in brain stem processing. However, a subsequent experiment by Rowan & Lutman (2005) indicated, in contrast, that multi–hour training did lead to learning with ITD and at both low- and high-frequencies, with time–courses that were at least broadly comparable to Wright & Fitzgerald’s (2001) data on ILD. However, potentially important differences in methodologies between the two studies complicate comparisons of learning. The primary aim of the present study was to estimate the time-course of learning on ILD using Rowan & Lutman’s (2005) general methodology to enable a more direct comparison of the time-courses between ILD and ITD. Twelve naïve listeners participated in this experiment. ILD thresholds were measured using a forced choice task combined with an adaptive procedure. Thresholds at 128 Hz and 4000 Hz were measured with all listeners during pre- and post-test sessions, nominally separated by 11 days. Between pre- and post-tests, six listeners received training consisting of repeated measurements at 4000 Hz only over 6 separate days amounting to 2160 trials; the others served as untrained controls. ILD thresholds at the trained frequency (4000 Hz) were found to reduce between pre- and post-test in both groups but the trained group learned significantly more than untrained group. The time course of learning appeared broadly comparable with that found by Rowan & Lutman (2005) with low– and high–frequency ITD and Wright & Fitzgerald (2001) with ILD at high–frequency. The implications of these results and suggestions for more detailed statistical investigations of time-course of learning will be discussed.

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Contributors

Author: D. Rowan

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