Listening for the norm: Adaptive coding in speech categorization

Abstract

Perceptual aftereffects have been referred to as "the psychologist's microelectrode" because they can expose dimensions of representation through the residual effect of a context stimulus upon perception of a subsequent target. The present study uses such context-dependence to examine the dimensions of representation involved in a classic demonstration of "talker normalization" in speech perception. Whereas most accounts of talker normalization have emphasized talker-, speech-, or articulatory-specific dimensions' significance, the present work tests an alternative hypothesis: that the long-term average spectrum (LTAS) of speech context is responsible for patterns of context-dependent per- ception considered to be evidence for talker normalization. In support of this hypothesis, listeners' vowel categorization was equivalently influenced by speech contexts manipu- lated to sound as though they were spoken by different talkers and non-speech analogs matched in LTAS to the speech contexts. Since the non-speech contexts did not possess talker, speech, or articulatory information, general perceptual mechanisms are implicated. Results are described in terms of adaptive perceptual coding. © 2012 Huang and Holt.