Poster #61 - Observed changes in infant arm movements before and after the emergence of reaching.

• In Event: Poster Session 20

Abstract

The ability to reach for objects is crucial to daily activities and for interacting with the environment. Reaching, however, does not emerge overnight during infancy but instead develops through weeks and months of arm movement experiences. During the first few months of life, infants perform a plethora of arm movements directed towards their bodies that give way to goal-directed actions. We are interested in identifying what arm movements infants perform in the few weeks before the emergence of reaching.
Eight infants were followed weekly from 5 weeks before reach onset up to 5 weeks after reach onset. Novel objects were presented out of reach for 5s and then moved to within the infants’ reaching space. We video-coded infants’ arm movements and visual fixations during these object presentations using eye-tracking throughout the pre- and post-reaching periods.
Preliminary analyses identified two predominant types of movements: hand-at-midline clasps and hand-to-mouth contacts. Infants’ average durations and frequencies of these arm events increased as they neared reaching onset. Two to 3 weeks prior to reaching, infants exhibited a “burst” of activity in these arm events. Infants made frequent mouth contacts and midline hand clasps while maintaining visual fixation on the objects. The duration of these events reached up to 3700ms on average prior to reach onset. However, once infants started reaching, they decreased the duration of those arm movements drastically to 1300ms and mouth contacts to 400ms. The frequency of these events followed a similar trend. Mouth contacts occurred at 9.8 events/week in the weeks prior to reaching onset, however, these events decreased to 3.4 occurrences/week after reaching onset. Likewise, prior to reaching, midline clasping peaked up to 17 occurrences before dropping to 3.9 events/week after reach onset. This drastic drop in arm event frequencies occurred immediately in the first 2 weeks following reach onset while goal-directed reaching increased.
The fact that midline hand clasping and hand-to-mouth contacts intensified in the 2 weeks prior to reach onset and while infants were constantly visually fixating on the object, indicates that those arm movements and looking behavior may be precursors to the emergence of goal-directed reaching. However, following the first contact with the object, those precursory arm movements quickly decline to give rise to goal-directed reaching. From that time, infants display a shift from arm movements directed towards their bodies to ones directed towards objects in their environment.

Authors

• John Paul Connell, University of Tennessee - Knoxville
  Presenting Author

• Allison Tenorio, University of Tennessee, Knoxville

• Avery Peffer, University of Tennessee, Knoxville

• Anna Lynn, University of Tennessee,Knoxville

• Daniela Corbetta, University of Tennessee - Knoxville