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Abstract:
Recent research has resulted in a set of unresolved
controversies about the nature of auditory processing reflected by
Mismatch Negativity (MMN). Previous evidence does not clarify
whether MMN indexes acoustic, phonetic or phonemic discrimination.
Several recent investigations indicate that MMN indexes memory
traces that are modulated by language experience. The present study
investigated whether MMN reflects phonemic processing, using Hindi
bilabial (ba), dental (da) and retroflexed (Da) consonants. Small
variable MMNs were found to some of the deviants (but not all) that
fell across a bilabial-dental category boundary. However, no MMNs
were elicited to the dental-retroflexed contrasts, for either
group. Performance on behavioral identification and discrimination
tasks showed a similar pattern; both groups of speakers showed
poorer and slower performance for the dental-retroflex compared to
the bilabial-dental contrasts. These findings suggest that the
dental-retroflexed contrast was difficult to discriminate for
speakers of all language backgrounds. In a second experiment, we
found that attention to the stimuli enhances the MMN amplitude in
an English-speaking group. This finding indicates that attention
may be necessary to elicit MMN to fine acoustic-phonetic
distinctions.
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