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

Notes that 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 6 of them, all of which can be exemplified using the syllable /da/ as in dot and occur during dichotic listening. In each type of fusion, the robustness of the fused percept is observed against variation in 3 parameters: the relative onset time of the 2 opposite-ear stimuli, their relative intensity, and their relative fundamental frequency. Patterns of results are used to confirm the arrangement of the 6 fusions in a hierarchy, and supporting data are provided in an analysis of the mechanisms that underlie each with reference to speech. The 6 fusions are sound localization, psychoacoustic fusion, spectral fusion, spectral/temporal fusion, phonetic feature fusion, and phonological fusion. They occur at 3, perhaps 4, different levels of perceptual analysis. The 1st 2 levels are characterized by perceptual integration, the other(s) by perceptual disruption and recombination. (3 p ref)