Developmental research on the relationship between production and perception of coarticulation

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We examined the effects of preceding vowel /a/ on the categorization of masked stop consonants /p/ and /t/ which followed the vowel in successive vocalizations. In these experiments, a phonemic restoration was confirmed for adult subjects. We found that frequencies of second formant (F2) at the end of the vowel preceding /t/ increased in contrast with those of the vowel preceding /p/. It seems that F2 transitions in the preceding vowel are discriminative cues. The phonemic restoration was also found in infants, but the degree in infants was smaller than that in adults, indicating that temporal facilitation on phonemic perception occurs more lately in vocal development. Furthermore, there were a significant increment of identified rate on the stop consonants in proportion of age, and a significant correlation between the degree of phonemic restoration and the frequencies of F2 at the end of the vowel /t/ in each infant. These results suggest that production and perception of co-articulation depend each other, particularly in development. Before modeling, we did the research related to the change of the quantitative nature with the qualitative nature in the interface of the language. As a result, it just became clear that the most suitable value for co-articulation and acoustic characteristics in real time had an influence strongly on not only a limitation by co-articulation movement but also a limitation by perception.