Lateral asymmetry in attention for three-month-old human infants during face-to-face interaction with mother.

A soft grip the size of an adult index finger was placed in the palm of 3-month-old human infants during face-to-face interaction with their mothers. In a between-subjects experiment, half the subjects interacted with mother for 3 min with no grip, which was followed by a 3 min interaction with the grip in the left hand; for the other half, the grip was placed in the right hand in the second condition. A within-subjects experiment compared the grip interaction for 3 min first in one hand and then in the other. The grip did not significantly alter the infant's gaze at mother, smiling, or positive vocalizations. The movements of the hand with the grip were suppressed similarly for left and right hands. Lateral asymmetry was found for looking to the left side when the grip was in the left hand, compared to no lateral preference in looking during any other condition. The results support a model of right-side dominance for attention control in infants.