The effects of task exposure and simulated grasping experience upon the emergence of reaching

Based on previous research, three-month-old infants who received simulated grasping experience via "sticky mittens" showed increased object-directed activity relative to infants who did not receive experience (Needham et al., 2002). The current study wanted to examine the importance of the "stickiness" aspect of the "sticky mittens" experience. Thirty pre-reaching infants were followed for 16 consecutive days. Each infant was randomly assigned to one of three groups: Velcro (grasping simulation), non-Velcro (no grasping simulation), or Control (no experience). On the first day of the study all infants visited our laboratory for a baseline assessment without mittens to ensure they were unable to reach. The Velcro and non-Velcro groups were seen in their homes from days two through 15 by an experimenter to receive their training. All infants returned to our laboratory on day 16 of the study to reassess their reaching skills without mittens.All testing conditions were held constant over the 16 days. Infants sat in a custom-designed infant chair behind a small table. The experimenter faced the infant and placed toys one-at-a-time onto the table within infants' reaching space. Trials lasted one minute and infants received 10 trials each day. Results showed that both the Velcro and non-Velcro groups significantly increased their amount of intentional reaching between the first and final days. When intentional reaching was examined day-by-day, only the non-Velcro babies showed a sustained increase from week one to week two, while the Velcro babies' rate tended to decline. Analysis of the duration of visual attention to the toy indicated that the non-Velcro group tended to pay more attention to the toy as compared to the Velcro group. Analysis of the kinematic measures showed that the Velcro and non-Velcro groups spent a significantly greater percentage of time closer to the toy after they were exposed to the training.These results suggest that simulated grasping experience did not provide an advantage to the Velcro group in learning to reach. Rather, it is argued here that repeated, task-specific experience, not simulated grasping, may be more important for the development of reaching.