ASA 125th Meeting Ottawa 1993 May

2pPP20. Use of the psychophysical method of adjustment in tonal pattern discrimination.

Charles S. Watson

Gary R. Kidd

Aimee Surprenant

Ward R. Drennan

Dept. of Speech and Hear. Sci., Indiana Univ., Bloomington, IN 47405

A difficulty in tonal-pattern research is that several thousand trials are typically required to approach asymptotic discrimination performance under minimal-uncertainty testing conditions. One solution to this problem is to use the method of adjustment to determine thresholds, rather than a forced-choice psychophysical method. In this study the extremely brief times that are required for a listener to achieve perceptual isolation for single components of a multi-tone patterns using the method of adjustment instead of a forced-choice method (minutes as opposed to hours) are demonstrated. A quantitative criterion for ``perceptual isolation'' reached when a frequency match is made that is as close to the standard as can be achieved when the standard and variable tones are both presented in isolation, rather than in pattern contexts. Not all adjustments are this accurate, however. The most useful distinction between difficult and easy adjustments is shown to be the percent of all the adjustments, for a given combination of target and context tones, that meet this perceptual-isolation criterion.