RESUMEN
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.
Asunto(s)
Desarrollo Infantil/fisiología , Conducta del Lactante/fisiología , Destreza Motora/fisiología , Caminata/fisiología , Femenino , Mano , Fuerza de la Mano , Humanos , Lactante , MasculinoRESUMEN
From birth, infants move their bodies in order to obtain information and stimulation from their environment. Exploratory movements are important for the development of an infant's understanding of the world and are well established as being key to cognitive advances. Newly acquired motor skills increase the potential actions available to the infant. However, the way that infants employ potential actions in environments with multiple potential targets is undescribed. The current work investigated the target object selections of infants across a range of self-produced locomotor experience (11- to 14-month-old crawlers and walkers). Infants repeatedly accessed objects among pairs of objects differing in both distance and preference status, some requiring locomotion. Overall, their object actions were found to be sensitive to object preference status; however, the role of object distance in shaping object encounters was moderated by movement status. Crawlers' actions appeared opportunistic and were biased towards nearby objects while walkers' actions appeared intentional and were independent of object position. Moreover, walkers' movements favoured preferred objects more strongly for children with higher levels of self-produced locomotion experience. The multi-target experimental situation used in this work parallels conditions faced by foraging organisms, and infants' behaviours were discussed with respect to optimal foraging theory. There is a complex interplay between infants' agency, locomotor experience, and environment in shaping their motor actions. Infants' movements, in turn, determine the information and experiences offered to infants by their micro-environment.
Asunto(s)
Desarrollo Infantil/fisiología , Destreza Motora/fisiología , Percepción Visual/fisiología , Caminata/fisiología , Femenino , Humanos , Lactante , Conducta del Lactante/fisiología , MasculinoRESUMEN
The stability and adaptability of visuomotor representations for hand movement in young children was investigated using a visuomotor adaptation paradigm in which the real-time visual feedback of pen movement was rotated 45 degrees clockwise during exposure trials. Four, six, and eight-year-old children performed line drawings to visual targets, from a common centered position ("center-out task"), in the horizontal plane under normal (pre-, and post-exposure), and rotated (exposure) visual feedback conditions. Analysis of pre-exposure trials indicated that older children performed faster, straighter, smoother, and showed more patterned movements than the younger children. Initial direction of movement, computed at 80 ms after movement onset, showed a progressive tuning of movement direction with increasing age. On introduction of the screen cursor rotation, all age group children showed improvement in their planning (initial directional error) and execution (movement time, movement length, root mean square error, and normalized jerk) error scores from early to late-exposure trials, but the 4-year-olds were less affected than older age children by the distortion during the early exposure period. Moreover, only the oldest group of children showed significant after-effects during post-exposure trials indicating that only this age group learned the internal model of the distorted environment. The absence of after-effects for initial movement direction observed in the two younger age groups suggest that these children might have less developed (i.e. more broad) internal visuomotor representations for hand movements, and that their internal representations are sharpened (i.e. tuned) with visuomotor experience.