ASA 125th Meeting Ottawa 1993 May

3pPP2. The relative contributions of targets and distractors in laterality judgments.

R. H. Dye, Jr.

Parmly Hearing Inst., Loyola Univ., 6525 N. Sheridan Rd., Chicago, IL 60626

A stimulus classification paradigm that allows the estimation of the relative contributions of target and distractor components of judgments of perceived laterality was used to assess the effect of frequency separation ((Delta)f). A 753-Hz tone was the target and the distractor was 553, 603, 653, 703, 728, 778, 803, 853, 903, or 953 Hz. The duration of the tones, which were gated simultaneously, we either 25 or 100 ms. Each block of 100 trials presented the target and the distractor at ten different interaural delays, with each combination presented once. Preceding the test interval was a diotic presentation of the target. Subjects indicated whether the target component appeared to the left or right of the intracranial midline. Left--right judgments were plotted as a joint function of the target and distractor delays. The slope of the best-fitting linear boundary between left and right responses was used to estimate the relative weights given to the target and the distractor. The target weights were greater for 100-ms durations and decreased as (Delta)f fell below 100 Hz. For all conditions, left--right judgments were partially dependent on distractor delay. [Work supported by NIH.]