Developmental changes in sound localization precision under conditions of the precedence effect.

DEVELOPMENTAL CHANGES IN SOUND LOCALIZATION PRECISION UNDER CONDITIONS OF THE PRECEDENCE EFFECT SEPTEMBER, 1991 RUTH Y. LITOVSKY, B.A., WASHINGTON UNIVERSITY M . A . , WASHINGTON UNIVERSITY Ph . D . , UNIVERSITY OF MASSACHUSETTS Directed by: Professor Rachel K. Clifton In enclosed spaces, the first sound that reaches the ears emanates directly from the original source, and is followed by reflections of the same sound off nearby surfaces. The ability to suppress the echoes is thought to minimize distraction and facilitate accurate localization of the original sound source. The ability to give perceptual priority to the original sound source under these conditions has long been known, and has been termed the "law of the first wave-front", or the "precedence effect" (PE). This phenomenon has been studied with respect to whether subjects perceive the presence of the lagging sound. Past developmental research on the PE has only considered the precision with which the leading or lagging stimulus can be located to a hemifield. Moreover, little attention has been paid to the influence that echoes exert on localization accuracy for the leading sound.