Index of content:
Volume 107, Issue 5, May 2000
- SPEECH PERCEPTION 
107(2000); http://dx.doi.org/10.1121/1.428655View Description Hide Description
This study examined neurophysiologic correlates of the perception of native and nonnative phonetic categories. Behavioral and electrophysiologic responses were obtained from Hindi and English listeners in response to a stimulus continuum of naturally produced, bilabial CV stimuli that differed in VOT from −90 to 0 ms. These speech sounds constitute phonemically relevant categories in Hindi but not in English. As expected, the native Hindi listeners identified the stimuli as belonging to two distinct phonetic categories (/ba/ and /pa/) and were easily able to discriminate a stimulus pair across these categories. On the other hand, English listeners discriminated the same stimulus pair at a chance level. In the electrophysiologic experiment N1 and MMN cortical evoked potentials (considered neurophysiologic indices of stimulus processing) were measured. The changes in N1 latency which reflected the duration of pre-voicing across the stimulus continuum were not significantly different for Hindi and English listeners. On the other hand, in response to the /ba/–/pa/ stimulus contrast, a robust MMN was seen only in Hindi listeners and not in English listeners. These results suggest that neurophysiologic levels of stimulus processing reflected by the MMN and N1 are differentially altered by linguistic experience.
107(2000); http://dx.doi.org/10.1121/1.428656View Description Hide Description
Adult listeners are able to recognize speech even under conditions of severe spectral degradation. To assess the developmental time course of this robust pattern recognition,speech recognition was measured in two groups of children (5–7 and 10–12 years of age) as a function of the degree of spectral resolution. Results were compared to recognition performance of adults listening to the same materials and conditions. The spectral detail was systematically manipulated using a noise-band vocoder in which filtered noise bands were modulated by the amplitude envelope from the same spectral bands in speech. Performance scores between adults and older children did not differ statistically, whereas scores by younger children were significantly lower; they required more spectral resolution to perform at the same level as adults and older children. Part of the deficit in younger children was due to their inability to utilize fully the sensory information, and part was due to their incomplete linguistic/cognitive development. The fact that young children cannot recognize spectrally degraded speech as well as adults suggests that a long learning period is required for robust acoustic pattern recognition. These findings have implications for the application of auditory sensory devices for young children with early-onset hearing loss.
An investigation of current models of second language speech perception: The case of Japanese adults’ perception of English consonants107(2000); http://dx.doi.org/10.1121/1.428657View Description Hide Description
This study reports the results of two experiments with native speakers of Japanese. In experiment 1, near-monolingual Japanese listeners participated in a cross-language mapping experiment in which they identified English and Japanese consonants in terms of a Japanese category, then rated the identifications for goodness-of-fit to that Japanese category. Experiment 2 used the same set of stimuli in a categorial discrimination test. Three groups of Japanese speakers varying in English-language experience, and one group of native English speakers participated. Contrast pairs composed of two English consonants, two Japanese consonants, and one English and one Japanese consonant were tested. The results indicated that the perceived phonetic distance of second language (L2) consonants from the closest first language (L1) consonant predicted the discrimination of L2 sounds. In addition, this study investigated the role of experience in learning sounds in a second language. Some of the consonant contrasts tested showed evidence of learning (i.e., significantly higher scores for the experienced than the relatively inexperienced Japanese groups). The perceived phonetic distance of L1 and L2 sounds was found to predict learning effects in discrimination of L1 and L2 sounds in some cases. The results are discussed in terms of models of cross-language speech perception and L2 phonetic learning.