Preparation for grasping an object: A developmental study.

Abstract

The development of visually controlled grasping actions was studied in two experiments. An optoelectronic technique (SELSPOT) was used to monitor the opening and closing of the hand during reaching actions by measuring the change in the distance between thumb and index finger. The purpose of Experiment 1 was to establish an adult criterion for the development. It was shown that adults started closing the hand around the target well before touch and that the timing was dependent on the size of the target. The hand started to close earlier when grasping a small rather than a large target. In addition, the degree of hand opening was also less for a small than for a large target. In Experiment 2 it was shown that infants who were 5-6, 9, and 13 months of age also controlled their grasping actions visually and started closing the hand around the target in anticipation of the encounter rather than as a reaction to the encounter. However, the strategy of the two younger age groups was different from that of adults. They started closing the hand closer to the time of contact with the target than did the 13-month-olds, who were comparable to adults in this respect. The timing was not dependent on the size of the target in any of the infant groups. In all age groups, reaching and grasping were most commonly organized in a continuous way; that is, the hand started to close without any interruption in the approach. The opening of the hand was found to be adjusted to target size in the 9- and 13-month-olds but not in the 5-6 month olds.

Fitting objects into holes: On the development of spatial cognition skills.

“…Already from birth, infants can direct their arm toward an object (von Hofsten 1982; van der Meer 1997), but it is not until four or five months that can they grasp it (von Hofsten and Rönnqvist 1988). When infants are going to grasp, they must plan their actions.…”

“…When a series of pictures was shown in a certain order, two-and three-month-old infants learned to move their gaze to where the object would reappear next (Wentworth and Haith 1998). Six-month-old infants reach their hand towards an object and open it in advance, rotate it so that their grasp will fit the object, and begin to close their hand before it arrives at the object (Lockman, Ashmead et al 1984;von Hofsten and Fazel-Zandy 1984;von Hofsten and Rönnqvist 1988;McCarty, Clifton et al 2001;von Hofsten 2007). Accordingly, this shows that by this age, infants have acquired so much knowledge of an object that they can grasp it.…”

“…Although grasping movements have been observed in newborns, it is not until they are about four five months old that they successfully grasp objects (von Hofsten and Fazel-Zandy 1984;von Hofsten and Rönnqvist 1988). When manipulating an object with the hand, it must adjust to the physical characteristics of the object (like form and size), spatial characteristics (like how the object is oriented) and temporal characteristics (like when you have to close your hand) (Lockman, Ashmead et al 1984;von Hofsten and FazelZandy 1984;von Hofsten and Rönnqvist 1988).…”

“…To succeed with a grasping experiment the hand must pre-adjust to the physical aspects and orientation of the object, and then close around it (von Hofsten and Rönnqvist 1988;McCarty and Ashmead 1999;McCarty, Clifton et al 2001;Oztop, Bradley et al 2004). In fitting objects into holes, the object must be used as an instrument on another object (Connolly and Dalgleish 1989;McCarty, Keen et al 2001).…”

“…Underlying perceptual development Perception and discrimination of sizes Already at five months, infants use visual information to control their hand movements to grasp differently sized objects (von Hofsten and Rönnqvist 1988). At nine months, infants adjust the opening of their hand to the size of the target.…”