Predictive action in infancy Evidence of early prospective behavior

Abstract: How do young infants understand and act on their constantly changing environment? An action perspective on motor development was taken into account. The present thesis investigated perception guided predictive action in 6-month-old infants, namely, head tracking and reaching for an object moving on a pre-defined trajectory, linear or nonlinear, fully visible or partially occluded. The motion trials were presented in a randomized order or in a way by using an ABBA block design.Study I of this thesis began with the exploration of the principles underlying infant predictive action. Infants were presented a fully visible moving object on four trajectories: two linear trajectories that intersected at the center of a display and two non-linear trajectories that contained a sudden turn at the point of intersection. The results supplied evidence that both infants’ head tracking and reaching showed an extrapolation of the object’s motion on linear paths, which was described by the principle of inertia. No learning effect was found in spite of repeated fully visible trials. Previous experiments reported that infants of similar age showed a reduction in reaching when object motion was occluded briefly.Thus Study II was undertaken, in part, to evaluate whether differences in the tasks resented to infants or differences in the visibility of the objects account for these findings. This was done by investigating infants’ predictive head tracking of an object following the procedure presented in Study I with only one exception: object motion was partially occluded by a small occluder positioned on the motion trajectory. Study II also raised a second question concerning infants’ ability to learn to anticipate upcoming object motions. It was found that infants were able to quickly learn to anticipate either linear or nonlinear motion but with a superior learning effect from linear motion. This pattern suggested a tendency to anticipate the upcoming motion in accord with inertia. Although a capacity to anticipate occluded object motion in accord with inertia was present, it was weak, as infants’ initial reaction to the occluded object motion revealed no such tendency. Learning in all cases was associated with the trajectory of the object, not the specific locations at which the object appeared. It was suggested that infants might form object representations that are influenced by learning and that are just weakly biased toward inertia extrapolation. This finding supported the claims that occlusion reduces the presentation of object representation, as suggested by single system of object representation theory.