Auditory and linguistic processes in speech perception: Inferences from six fusions in dichotic listening.

Abstract

A number of phenomena in speech perception have been called fusion, but little effort has been made to compare these phenomena in a systematic fashion. The present paper examines six of them. All can be exemplified using the syllable /da/ as in dot, and all occur during dichotic listening. In each type of fusion, the robustness of the fused percept is observed against variation in three parameters: the relative onset time of the two opposite-ear stimuli, their relative intensity, and their relative fundamental frequency. Patterns of results are used to confirm the arrangement of the six fusions in a hierarchy, and supporting data are summoned in an analysis of the mechanisms that underlie each with reference to speech. The six fusions are sound localization, psychoacoustic fusion, spectral fusion, spectral/temporal fusion, phonetic feature fusion, and phonological fusion. They occur at three, perhaps four, different levels of perceptual analysis. The first two levels are characterized by perceptual integration, the other (s) by perceptual disruption and recombination.