Navigation in 9-month-old infants’ reach to grasp

Authors

• C Gammon
• C Mash
• MH B

Abstract

Adults have a propensity when reaching for objects to circumnavigate other objects in the vicinity, even when those objects are not on the direct path to the target. Lesion studies with neurological patients suggest that the dorsal stream vision-for-action pathway is involved in guiding the automated avoidance seen in healthy subjects. The present work examined 30 9-month-old infants in a reach-to-grasp task involving multiple objects. Research on infants and young children has suggested that the dorsal stream may have a more protracted developmental time course than other visual system structures. Infants were outfitted with motion-analysis sensors on their wrists and presented with a visually salient target object when either no other objects were present in their manual workspace or when a simple, smaller, and less salient object was placed in the workspace at one of four positions around the target object. None of the four positions of the second object occluded infants’ direct reach toward the target. Reach movements were compared between target-only and target-with-other conditions. Target-only reaches were straighter than when a second object was present in the manual workspace, and target-only reaches also took less time to complete. By 9 months, infants’ non-target accommodation in reach-to-grasp movements has begun to resemble that of adults when multiple objects are present in the workspace. To the extent that the behavioral propensity to accommodate extra objects in the workspace is guided by dorsal stream activity, the development of such function appears likely underway by 9 months of age.

Scientific Focus Area: Social and Behavioral Sciences

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