Discrimination of voice onset time in infancy.

In an effort to determine whether infants can discriminate speech sounds on the basis of a single acoustic cue, timing onset of periodic voicing, two experiments were conducted employing synthetic speech sounds. Naturally produced syllable pairs were also used for comparison. In the first experiment infants evidenced discrimination of a naturally produced /ba/ versus /pa/ pair and a naturally /du/ versus /tu/ pair. In addition, infants discriminated a synthetic /ba/ versus /pa/ contrast that was cued by several acoustic differences in addition to timing onset of periodic voicing but failed to evidence an ability to discriminate a synthetic /du/ versus /tu/ contrast that contained flat first formants and differed only in timing onset of periodic voicing. A second experiment was conducted in which infants once again evidenced discrimination of naturally produced /du/ versus /tu/ stimuli but not of synthetic /du/ versus /tu/ stimuli containing slight first-formant transitions. These results suggest that timing onset of periodic voicing alone may not be a sufficient cue for infant discrimination of English voicing contrasts.