ピッチ変化音に対する4-10ヶ月齢児の反応

The present study examined whether infants discriminate between two types of synthesized auditory stimuli (not the human voice) by using head-turn-preference procedure (HPP). The auditory stimuli used in this study consisted of the fundamental frequency and several harmonics of that frequency synthesized by a computer. Two types of sounds were administered to 16 4-to 10-month-old infants: (1) pitch-modulated sounds where frequency changed over time, and (2) flat sounds where frequency did not change over time. In HPP, the duration of an infant\u27s attention to each of these two types of stimuli was measured. It was found that infants demonstrated a significant preference for the pitch-modulated sounds. This study also examined whether there is an age-related difference in preference for these sounds by comparing two age groups: (1) a younger group (8 infants, 4 to 6 months of age), and (2) an older group (8 infants, 7 to 10 months of age). It was found that the younger group showed a significant preference for the pitch-modulated sounds in contrast to the older group which showed no significant preference for one type of sound over the other. These findings suggest that auditory information modulated over time is potentially meaningful to the younger infant. This might be the case when mothers talking to infants tend to use highly-pitched or exaggerated voice. The pitch-modulated sounds are discussed in terms of their similarity to the infantdirected-speech of mothers within the context of the mother-infant interaction, as well as its potential influence on early perceptual development