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The Transition to Reaching: Mapping Intention and Intrinsic Dynamics
Author(s) -
Thelen Esther,
Corbetta Daniela,
Kamm Kathi,
Spencer John P.,
Schneider Klaus,
Zernicke Ronald F.
Publication year - 1993
Publication title -
child development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.103
H-Index - 257
eISSN - 1467-8624
pISSN - 0009-3920
DOI - 10.1111/j.1467-8624.1993.tb04188.x
Subject(s) - coactivation , psychology , task (project management) , motor skill , developmental psychology , physical medicine and rehabilitation , dynamics (music) , movement (music) , cognitive psychology , electromyography , neuroscience , medicine , physics , pedagogy , management , acoustics , economics
The onset of directed reaching demarks the emergence of a qualitatively new skill. In this study we asked how intentional reaching arises from infants' ongoing, intrinsic movement dynamics, and how first reaches become successively adapted to the task. We observed 4 infants weekly in a standard reaching task and identified the week of first arm‐extended reach, and the 2 weeks before and after onset. The infants first reached at ages ranging from 12 to 22 weeks, and they used different strategies to get the toy. 2 infants, whose spontaneous movements were large and vigorous, damped down their fast, forceful movements. The 2 quieter infants generated faster and more energetic movements to lift their arms. The infants modulated reaches in task‐appropriate ways in the weeks following onset. Reaching emerges when infants can intentionally adjust the force and compliance of the arm, often using muscle coactivation. These results suggest that the infant central nervous system does not contain programs that detail hand trajectory, joint coordination, and muscle activation patterns. Rather, these patterns are the consequences of the natural dynamics of the system and the active exploration of the match between those dynamics and the task.