Neurophysiologic correlates of cross-language phonetic perception

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.