A reconsideration of intensity‐based duplex perception for speech.

Abstract

Duplex perception (DP) occurs when one stimulus component simultaneously contributes to two distinct percepts. In one potential demonstration, a sinusoidal glide is substituted for an F3 transition in a /da/ or /ga/ syllable, and the glide is claimed to distinguish the consonant while simultaneously being separately perceived as a nonspeech chirp. Recent concerns regarding the validity of evidence for this variant of DP were addressed using theoretically bias‐free psychophysical methods. Individual thresholds for consonant, and chirp, perception were compared as a function of glide intensity. Consistent with DP, consonant identification and discrimination were maintained at glide intensities well below chirp detection threshold. Listeners also could not reliably match isolated glides to glides in speech context, indicating that consonants were not simply inferred from the perception of isolated glides. Methodological implications of the results are discussed, including the need to insure that the nature of consonant perception depends upon the mixture of a given glide with the remainder of the syllable. An alternative, and potentially more reliable method for evaluating chirp detection threshold also is provided. [Work supported by NIH.]