Effects of voice‐onset time duration, and number of adaptor repetitions on the scaling of stop consonant voicing

This investigation examined the effects of duration and number of repetitions of the adapting stimulus on the voicing feature scaling of stimuli varying in VOT before and after adaptation. The adapting stimuli and trials were varied as follows: (1) the adapting stimulus was either 5, 25 or 55 ms VOT, and (2) the number of repetitions during each adaptation trial was 5, 32 or 95. Fifteen subjects used a six‐point rating scale in responding to both preadaptation and adaptation identification stimuli. The major findings of this study were as follows: (1) The 55‐ms adaptor was rated as p‐like and the 5 and 25 ms adaptors were rated as b‐like, (2) generally greater phonetic boundary shifts occurred after adaptation with the 55‐ms adaptor than with the 5‐ or 25‐ms adaptors and with the 5‐ms adaptor than with the 25‐ms adaptor, (3) significantly greater phonetic boundary shifts occurred with 32 and 95 repetitions than with 5 repetitions, and (4) significant changes in rating responses occurred for other than boundary stimuli. The results support the following conclusions: (1) Rating changes support a fatigue type model that assumes modification in the sensitivity to boundary and end point VOT stimuli, (2) effects of adaptor repetition support an auditory component of voicing analysis, and (3) adaptor percept influences direction of shift while the acoustic nature of the adaptor influences magnitude of shift.