Systems in development: motor skill acquisition facilitates three-dimensional object completion

Abstract

How do infants learn to perceive the backs of objects that they see only from a limited viewpoint? Infants' 3-dimensional object completion abilities emerge in conjunction with developing motor skills--independent sitting and visual-manual exploration. Infants at 4.5 to 7.5 months of age (n = 28) were habituated to a limited-view object and tested with volumetrically complete and incomplete (hollow) versions of the same object. Parents reported infants' sitting experience, and infants' visual-manual exploration of objects was observed in a structured play session. Infants' self-sitting experience and visual-manual exploratory skills predicted looking at the novel, incomplete object on the habituation task. Further analyses revealed that self-sitting facilitated infants' visual inspection of objects while they manipulated them. The results are framed within a developmental systems approach, wherein infants' sitting skill, multimodal object exploration, and object knowledge are linked in developmental time.

Figure 1

Toys offered to infants for exploration during the manual skills assessment.

Figure 2

Sketch of computer-generated displays used during visual habituation. A) The habituation display was a wedge-shaped object pivoting 15° in depth. B) The complete test display was a symmetric interpretation of the habituation display rotating 360° in depth. C) The incomplete test display was a hollow form composed only of the surfaces seen during habituation that also rotated 360° in depth.

Figure 3

Individual infants’ contributions to each predictor variable. Mean values are represented by horizontal lines on each plot. A) Post-habituation looking preferences toward the incomplete object display. B) Infants’ ages at testing in days. C) Days of tripod and self-sitting experience. D) Number of drops of toys during play. E) Number of bouts of rotations, fingerings, and transfers without looking at toys during play. F) Number of bouts of rotations, fingerings, and transfers with looking at the toys during play.

Figure 4

Mean number of bouts (with and without looking at the toys) of A) rotations B) fingering and C) transfers during the structured play session grouped by infants’ independent self-sitting ability. Error bars represent standard errors of the mean. Self-sitters more frequently manipulated objects while they were looking at them compared to not looking at them, but non-sitters manipulated objects while looking and not looking at them equally.