Identification of sine‐wave analogues of CV syllables in speech and nonspeech modes

Adults discriminate categorically successive from simultaneous coterminous acoustic events—a psychoacoustic capability which may account for infants' sensitivity to contrasts in stop‐consonant voicing. Can adults demonstrate an analogous capability to explain infants' sensitivity to contrasts in stop place? We synthesized a set of [vV‐dV] “asymmetric” speech continua whose phoneme boundaries did not correspond to any obvious discontinuity:boundaries were not characterized by level formant transition trajectories nor did they fall at the centers of stimulus ranges. Each syllable was modelled by replacing the first three formants with frequency and amplitude modulated sine waves. A modified AXP discrimination paradigm in which X was a member of a continuum and A and B were continuum endpoints provided “identification” data for both types of stimulus. Initially, sine‐wave continua were categorized symmetrically while their constituents were perceived as “whistles.” In later sessions, however, listeners volunteered that these patterns afforded consonantal percepts and categorized both sine‐wave and formant continua asymmetrically. We are continuing to experiment with this paradigm which provides identification data without requiring overt labelling. We note that our present results provide no evidence of a psychoacoustic basis for sensitivity to place of production contrasts.