The development of prehension in infants.
AbstractThe arm and hand of the neonate are not under cortical control, but they possess the capacity for orderly and cooperative functioning. Prehension is a response to an object already located visually. There is convincing evidence that, at the age at which the present study begins, vision is adequate for sighting the object. The method used in the present study of infant prehension was a motion and frame-by-frame analysis of cinema records of infant prehension of 1-in. red cubes. With the exception of the youngest (sixteen weeks) group, all the subjects made immediate attempts to grasp the cube. However, few infants actually secured it until they were twenty-eight weeks of age. Overreaching and underreaching occurred frequently at twenty to thirty-two weeks. Raising and lowering the fingers, raising the hand, scratching the table top, or rubbing it with the heel of the hand, while regarding the cube, were common at sixteen to twenty-four weeks. Increase in the number and variety of manipulative and exploitative activities accompanies improvement in the technique of prehension. Active manipulation really begins at twenty-eight weeks and is associated with radial prehension (grasping mainly by thumb, forefinger, and middle finger) and rotation of the forearm, which brings the cube into view for inspection. The viselike grip is giving way slowly to adaptive holding. With the advent of digital prehension (grasping by the fingers), the infant begins to adjust the pressure of his grip to the weight of the cube. (PsycINFO Database Record (c) 2009 APA, all rights reserved)