Toy-oriented changes during early arm movements: Hand kinematics
In a recent cross-sectional study, we found that young infants changed their spontaneous arm movements in the presence of a toy, termed ‘toy-oriented changes’, in systematic ways beginning many weeks before their first consistent reaches [Bhat, A. N., Heathcock, J. H., & Galloway, J. C. (2005)....
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Published in | Infant behavior & development Vol. 29; no. 3; pp. 358 - 372 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
New York, NY
Elsevier Inc
01.07.2006
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | In a recent cross-sectional study, we found that young infants changed their spontaneous arm movements in the presence of a toy, termed ‘toy-oriented changes’, in systematic ways beginning many weeks before their first consistent reaches [Bhat, A. N., Heathcock, J. H., & Galloway, J. C. (2005). Toy-oriented changes in hand and joint kinematics during the emergence of purposeful reaching. Infant Behavior and Development,
28(4), 445–465]. The purpose of the present study was to test specific hypotheses regarding toy-oriented changes in a longitudinal design.
Thirteen infants were observed every other week from 8 weeks of age up to the onset of reaching. At each session, hand and joint motions were observed with and without a toy present using a high-speed motion capture system. This paper focuses on the toy-oriented changes in
hand variables.
As predicted, infants displayed a meaningful pattern of toy-oriented changes, which systematically changed as infants approached the first week of reaching. During the
Early phase (8–10 weeks before reaching), infants scaled down their movement length and speed in the presence of a toy. During the
Mid phase (4–6 weeks before reaching), infants scaled up movement number and speed, increased movement smoothness, and decreased their hand–toy distance in the presence of a toy. During the
Late phase (within 2 weeks of reaching), infants continued to change their hand's position to get closer to the toy and began contacting it. Interestingly, movement number and smoothness displayed similar developmental patterns, where movement length and speed displayed similar patterns.
Toy-oriented adaptation of arm movements emerges in the first months of life and forms a complex, yet tractable continuum with purposeful reaching. These results provide a foundation to test more specific hypotheses of hand and joint coordination in both typically developing infants and those infants born at risk for coordination impairments. |
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ISSN: | 0163-6383 1879-0453 1934-8800 |
DOI: | 10.1016/j.infbeh.2006.01.005 |