A study of reaching actions in walking infants

- Infant walkers initiate reaching while walking but stand before contacting objects.
- Walking age is correlated with speed of manual object retrieval while upright.
- Adoption of bracing hand postures is correlated with months since walking onset.
- The degree of reach/walk overlap in time is a function of target height.
- Upper- and lower-body actions are flexibly integrated in reaching infant walkers.

Acquiring motor skills transforms the perceptual and cognitive world of infants and expands their exploratory engagement with objects. This study investigated how reaching is integrated with walking among infant walkers (n = 23, 14.5-15.5 months). In a walk-to-reach paradigm, diverse object retrieval strategies were observed. All infants were willing to use their upper and lower bodies in concert, and the timing of this coordination reflected features of their environment. Infants with an older walking age (months since walking onset) retrieved items more rapidly and exploited their non-reaching hand more effectively during object retrieval than did same-age infants with a younger walking age. This suggests that the actions of the upper- and lower-body are flexibly integrated and that this integration may change across development. Mechanisms that shape sophisticated upper-body use during upright object retrieval are discussed. Infants flexibly integrate emerging motor skills in the service of object retrieval in ways not previously documented.