Lateralization of infant holding by mothers: A longitudinal evaluation of variations over the first 12 weeks.

The maternal preference to hold infants on the left rather than right side of the body was examined longitudinally, with attention to 4 explanations: maternal monitoring of infant state, maternal handedness, infant proximity to the mother's heartbeat, and preferred infant head position. The side and site of holding were measured over the first 12 weeks of the lives of 24 infants. Information about group and individual consistency in holding side allowed novel evaluation of the theories. A strong bias to hold on the left dropped below significance when the infants were aged 12 weeks and was limited to specific holding positions. Findings were generally consistent with the monitoring hypothesis, and little support was found for the 3 alternative explanations.