title: Differences in human and monkey sensitivity to acoustic cues underlying voicing contrasts.
abstract: Humans and monkeys were compared in their differential sensitivity to various acoustic cues underlying voicing contrasts specified by voice-onset time (VOT) in utterance-initial stop consonants. A low-uncertainty repeating standard AX procedure and positive-reinforcement operant conditioning techniques were used to measure difference limens (DLs) along a VOT continuum from--70 ms (prevoiced/ba/) to 0 ms (/ba/) to + 70 ms (/pa/). For all contrasts tested, human sensitivity was more acute than that of monkeys. For voicing lag, which spans a phonemic contrast in English, human DLs for a/ba/(standard)-to-/pa/ (target) continuum averaged 8.3 ms compared to 17 ms for monkeys. Human DLs for a/pa/-to-/ba/ continuum averaged 11 ms compared to 25 ms for monkeys. Larger species differences occurred for voicing lead, which is phonemically nondistinctive in English. Human DLs for a /ba/-to-prevoiced/ba/ continuum averaged 8.2 ms and were four times lower than monkeys (35 ms). Monkeys did not reliably discriminate prevoiced /ba/-to-/ba/, whereas humans DLs averaged 18 ms. The effects of eliminating cues in the English VOT contrasts were also examined. Removal of the aspiration noise in /pa/ greatly increased the DLs and reaction times for both humans and monkeys, but straightening out the F1 transition in /ba/ had only minor effects. Results suggest that quantitative differences in sensitivity should be considered when using monkeys to model the psychoacoustic level of human speech perception.
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000818:Animals; D001307:Auditory Perception; D002521:Cercopithecus / Q000502:physiology*; D002522:Chlorocebus aethiops / Q000502:physiology*; D005260:Female; D000882:Haplorhini / Q000502:physiology*; D006801:Humans; D008251:Macaca / Q000502:physiology*; D008297:Male; D010700:Phonetics; D013045:Species Specificity; D014831:Voice