Object size as a determinant of grasping in infancy

Siddiqui, A. (1995, September). Object size as a determinant of grasping in infancy. The Journal of Genetic Psychology, 156(3), 345. Retrieved September 15, 2011, from Proquest.

This study sought to explore the time in which infants begin to grasp objects and also how this grasping is carried out. Researchers from a previous study observed infants and found that infants use the forearm and the hand, around the age of 16 months, to reach effectively. When the infant is close to 20 weeks old they began to use a palmer grasp. At 28 weeks, a radial grasp is used by the infant. Then at 40 weeks, the infant begins to use his or her index finger by extending it to an object. After this period, the thumb is utilized due to the changing muscular development in the arms. Recent studies have shown that, early on, infants begin to make adjustments with their hands and timing in position with the target. In this study infants grouped in the categories 5 months, 7 months, and 9 months, with 20 infants per group, were given 5 round objects of different  sizes either horizontally or vertically. The researchers observed the how the infants grasped for objects by monitoring which fingers were used while in the process of grasping. From the results, it was shown that 5 month olds mainly used 4 fingers when gripping the smaller objects. When grasping large objects there was an equal distribution among age groups since they both used all of their fingers from one hand or used both hands. The  results show  that infants of all of the age groups grasped based upon the size of the objects. For smaller objects fewer fingers were used, but for larger objects more fingers were used.  The older infants, however, were better at grasping both large and small objects consistently.