Visual exploration of reaching space during left and right arm movements in 6-month-old infants

Infant's manual laterality and eye-hand coordination emerge during the second part of the first year of life with the development of reaching. Nevertheless, little is known about the potential asymmetric characteristics of this coordination. The aim of this study was to describe visuo-spatial exploration in 6-month-old infants during reaching, according to the hand used. More specifically, we examined if the use of the left or the right hand was linked to a specific type of visual exploration. Gaze direction during goal-directed reaching towards an object placed on the table was measured with a remote ASL 504 eye tracker (Bedford MA). Twelve babies aged 6 months were observed during six reaching sessions, alterning three sessions with an object on the left side of the subject and three with an object on the right side. Gaze direction and some hand variables (hand activity, hand opening and hand position from the body) were coded with The Observer software. Results showed that babies visually explore their reaching space differently according to the hand used: they look more at the object when they use their right hand and more around the object when they use their left hand; they also look more often at their left hand than at their right one. These results suggest that an asymmetric visuo-manual coordination exists as early as 6 months: vision seems to support (1) left hand during reaching for evaluate distances from object to baby by means of visual feedbacks and (2) right hand for identify what sort of object is. Results are discussed in light of manual specialization and specific hemispheric skills at this age.