The holding of 465 Japanese infants by their mothers was longitudinally observed at 4 and 9 months with several checkups and questionnaires of physical and psychological development and child-care attitude in a larger longitudinal study of mother-child relationships. A left side bias in holding was significant for the 4-month-old infants. The infants' increased autonomy in their ability to adopt a posture at 9 months weakened the holding bias. The mothers' handedness was related to different right/left hand contact patterns, but it was significant only for holding on the left side. The infants' reflexes relating to posture did not correlate with the holding bias at 4 months. The meaning and possible determinants of holding laterality are discussed.
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