Experiments of vowel identification and dichotic fusion have been performed in order to investigate the condition in which two time-varing dynamic vowels would 'fuse'. Peripheral/central dichotomy of "complementary function" in the human auditory system between production and perception at the level of nonsense syllables has been considered by dealing with dichotic listening. Two types of stimuli, one of the form [u-Vowel-u] and the other [e-Vowel-e], were synthesized and presented dichotically to listeners. Judgment of fusion was made for the middle vowels of the stimuli. The results suggest that this kind of comprementality between production and perception of speech does not take place in peripheral auditory system.