Language or music? Environmental influences on infants' handedness from 5 to 12 months.

The main purpose of this study was to test the influence of music environment on hand-use preference in infants from 5 to 12 months, compared to speech environment. According to hemispheric specialization, our hypothesis was that infants would reach for objects more with their right hand in a speech context (left hemisphere), and more with their left hand in a music context (right hemisphere). 61 full-term infants aged from 5 to 12 months participated in this study. A prehension task was proposed successively in two sound environments (music and speech) in a counterbalanced order. Left-, right-movement and/or bimanual movements were scored. Results show that whatever the sound context, from 8 months a lateral right bias occurs and increases strongly. However, 5- to 7-months-old infants used more their left hand when they listen to a piece of classical music that an adult speech. Bimanual movements were more frequent at 6 and 7 months than unimanual movements in the speech condition. Results are discussed in terms of manual specialization.