The development of prehension in normal infants.

This study investigated the longitudinal development of prehension in 10 normal infants, 4 through 12 months of age. The infants' spontaneous prehensile responses to 2.54-centimeter (1-inch) red cubes, 1.27-centimeter (1/2-inch) red cubes, raisins, and plastic keys on chains were filmed with a Kodak Super 8 movie camera, transferred to videotape in slow motion, and analyzed. The 2.54-centimeter (1-inch) red cube data were compared to data gathered by Henry Halverson, noted authority in the area of prehension. Infants in both studies followed the same trend in their acquisition of prehensile skills, but the infants in the current study used most grasps at slightly earlier ages. The size and shapes of the objects presented influenced, but did not dictate, the grasps used. All grasps used by infants fall into three developmental phases: 1. using whole hands in an unspecialized manner; 2. using parts of hands as some specialization begins to develop; and 3. using the pads of distal phalanges or the tips of fingers in a specialized manner. The infants responded to the 3 presentations of like objects with the same grasp only 34 percent of the time, yet they were 65 percent consistent in using the same phase of prehensile development for the 3 presentations. Implications of these findings for developmentally disabled infants are discussed.