Enhanced discriminability at the phonetic boundaries for the voicing feature in macaques.

DiacrimiDation of apeech IOUDda from three computer-pnerated continua that ranged from volced to voiceleessyllables (/be.paI, Ida·taI, and Ip·bI) was tested with three macaques. The stimuli on .ch continuum varied in voice-onset time (VOT). Pain of stimuli that were equally different in VOT were chosen such that they were either withln-eategory pairs (syllables given the same phonetic label by human Hsteners) or between-eategory pairs (syllables given dif· ferent phonetic labels by human Hsteners). Results demonstrated that discrimination performance was always best for between-eategory pain of stimuli, thus repHcating the "phoneme boundary effect"seenin adultHatenen andin human infantsas youngas 1 month of age. The flndinp are discussed in terms of their specific impact on accounts of voicing perception in human Hsteners andin terms of theirimpactondiscussions of theevolution of language.