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Frame-by-Frame Video Analysis of Idiosyncratic Reach-to-Grasp Movements in Humans
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Development of reaching in infancy

Neil E Berthier1, Rachel Keen

  • 1Department of Psychology, University of Massachusetts, 135 Hicks Way, Amherst, MA 01003-9271, USA. berthier@psych.umass.edu

Experimental Brain Research
|December 13, 2005
PubMed

Insights

Infant reaching skill develops through increased smoothness, not speed. By two years, infant reaching movement patterns approach adult profiles, showing smoother, more controlled motions.

Area of Science:

  • Developmental psychology
  • Motor control
  • Human infant development

Background:

  • Understanding the developmental trajectory of reaching is crucial for assessing motor skill acquisition in infants.
  • Previous research has focused on various aspects of infant reaching, but longitudinal data on kinematic changes is limited.

Purpose of the Study:

  • To longitudinally analyze the kinematic development of reaching movements in human infants.
  • To identify age-related changes in reach speed and smoothness over the first two years of life.

Main Methods:

  • Longitudinal study of 12 human infants from reach onset to 20 months of age.
  • Utilized linear mixed-effects statistical modeling to analyze movement data.
  • Tracked kinematic variables including reach speed and movement jerk.

Main Results:

  • Reach speed gradually slowed with increasing age.
  • Movement jerk decreased more rapidly than speed, indicating increased smoothness.
  • Elbow joint usage evolved from a locked position to prominent use by 6 months.

Conclusions:

  • Infant reaching skill improves through increased movement smoothness rather than increased speed.
  • The kinematic profile of infant reaching approaches adult patterns by the second year of life.
  • Developmental changes in reaching are characterized by progressive refinement and control.

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