ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pPP3. The influence of pattern-based frequency expectations on resolving power for components of multitone sequences.

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

The effect of deviations from frequency expectations on resolving power for components of tonal sequences was studied with a method similar to that used earlier to determine the effect of temporal deviations [G. R. Kidd, 2966(A) (1994)]. In a same--different task, listeners were asked to compare the last two of four twelve-tone patterns presented on each trial. The first two patterns were identical and served to establish expectations from which the third and fourth patterns could deviate. In the third pattern, the frequency of a single ``target'' tone was lowered by either 3 or 7 semitones, or left unchanged. The frequency change to be detected was added to the target component in the fourth pattern on half the trials. Thresholds for this frequency increment were estimated for each deviation condition (as defined by the target-tone frequency used in the third pattern). Just as with deviations from temporal expectations, deviations from frequency expectations produced threshold increments that increased with the size of the deviation. These findings suggest that the superior discriminability typically observed with familiar patterns is due to the appropriate targeting of attention in frequency and in time during pattern presentation. [Work supported by NIDCD.]