Lack of laterality effect for monaural categorization of VOT and TOT stimuli

Sixteen right-handed males were tested for lateral preference and consistency of identification of stimuli differing in voice-onset time (VOT) or tone-onset time (TOT). A continuum of 10 stimuli of each type was presented monaurally to the right and left ears, and reaction times (RTs) were recorded each time a participant indicated a choice between a voiced [da] and a voiceless [ta] alternative for VOT, or between the presence of one type of tone or another for TOT. Results indicated that both classes of stimuli were perceived as having unique boundaries, with the TOT boundary being lower than that of the VOT continuum. VOTs were identified more quickly than TOTs, and the two ears did not differ in consistency or speed of identification for either condition. Results cannot be used to support the idea that the two hemispheres process voice-onset time differently than tone-onset asynchronies. In view of the absence of a right ear advantage for VOT, however, the use of a monaural task for eliciting hemispheric asymmetries is not recommended.