乳幼児の刺激音数の聴覚的弁別—実験設定と初期データ

Infants' auditory discrimination of the number of stimulus sounds:Experimental setup and preliminary data

　構音獲得過程の誤りでは，音節の脱落や付加といった音節数の誤りがみられる．この背景には音節数の知覚の問題が考えられるが，音節数の知覚に関する研究はほとんどない．そこで本研究では，乳幼児で刺激音数の弁別を調べることを目的とした．対象は7か月（男児）と1歳8か月（女児）の定型発達児2名とした．刺激音は複合音（200Hzの鋸波）と合成した言語音/ma/を用い，1単位，3単位，4単位の刺激音系列を作成した．対象児にはスピーカで刺激音系列を提示し，条件付け振り向き法で反応を捉えた．その結果，複合音の1単位から3単位では，7か月児は5施行中3施行，1歳8か月児は9施行中5施行で振り向き反応があった．以上より，条件付け振り向き法を用いた刺激音数の弁別の観察で1単位と3単位の違いを弁別していることが確認でき，条件付け振り向き法による検査が有用である可能性が示唆された．

　During the developmental process of articulation, errors in the number of syllables are observed. This may reflect a problem in the perception of the number of syllables, but there is little research available. The aim of this study is to investigate whether or not infants are able to discriminate the number of sounds. The subjects were two typically developing children, a 7-month-old boy and a 20-month-old girl. Stimulus sound series of one, three, and four units were created using a sawtooth wave (200Hz) and synthesized nonsense syllable /ma/. The stimuli were presented through the speaker, and children's responses were evaluated using the conditioned head turning procedure. The results showed that both children were able to discriminate between one unit and three units of sound. The results suggest that the conditioned head turning procedure can be useful for testing infants' auditory perception.