ASA 124th Meeting New Orleans 1992 October

1pPP10. The proportion-of-the-total-duration (PTD) rule holds for duration discrimination.

Gary R. Kidd

Charles S. Watson

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

In previous work, it was demonstrated that frequency resolving power for each individual component of an unfamiliar sequence of tones increases with the component's proportion of the total sequence duration [G. R. Kidd and C. S. Watson, J. Acoust. Soc. Am. (to be published)]. This work has now been extended to the case of duration discrimination. In this case, the dimension affected by changes in PTD (i.e., time) is also the primary dimension of variation within the patterns, as well as the dimension to which listeners must attend to perform the task. Listeners were asked to detect a change in the duration of a single tone in a five-tone pattern using a modified two-alternative forced choice procedure. Target-tone durations were determined by the PTD value (0.1, 0.2, or 0.4) and the total pattern duration (250 or 750 ms). Context-tone durations were determined randomly on each trial. A single frequency pattern, consisting of a sequence of ascending frequencies, was used throughout the experiment. The pattern of results obtained was essentially the same as that found in the frequency-discrimination experiments. Increases in the proportion of the total pattern duration occupied by the target tone consistently resulted in lower duration-discrimination thresholds. [Work supported by NIH with partial support from AFOSR to the Institute for the Study of Human Capabilities.]