18 巻 (2011) 3 号 p. 402-415
Previous studies indicated that looking to the right side facilitates the intermodal audiovisual matching of speech in infants (MacKain et al., 1983, Patterson & Werker, 1999). This study investigated the side bias effect for sounds containing rapidly changing temporal elements, i.e. a bilabial trill (BT). In Experiment 1, 8-month-old infants were presented with pairs of faces articulating a BT and a whistle (WL), respectively. The infants who listened to the BT showed successful audiovisual matching by orienting longer toward the sound-specified BT face only when the face was presented to the right side of the infants. This right-side bias was confirmed by the number of gaze shifts toward the BT face when it appeared in the right visual field. Such spatial asymmetry was not exhibited by the infants who listened to the WL, and the infants to whom no sound was presented. Experiment 2 tested 5-month-old infants on their audiovisual matching of the BT, and revealed that matching is acquired later than 5 months of age. The strong right-side bias found in Experiment 1 is argued from the perspective of left hemisphere dominance in the processing of the rapidly changing sound components of the BT.