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Postural control during reaching in young infants: a dynamic systems approach
1Department of Psychology, Indiana University, Bloomington 47405, USA. thelene@indiana.edu
Insights
Infant motor development shows posture and reaching skills emerge through a dynamic interplay. Head control stabilizes the body, enabling coordinated arm movements for successful reaching in early development.
Area of Science:
- Developmental Psychology
- Motor Control
- Ecological Psychology
Background:
- Postural stability is essential for goal-directed movements like reaching.
- Infant motor development involves complex coordination of multiple body systems.
- Schöner's dynamic model provides a framework for understanding coupled control levels.
Purpose of the Study:
- To conceptualize the coordinated development of posture and reaching in infants.
- To investigate the role of head and arm muscle coordination in early reaching.
- To apply a dynamic systems approach to infant motor acquisition.
Main Methods:
- Longitudinal study of four infants from 3 weeks to 1 year.
- Analysis of muscle activity patterns during reaching tasks.
- Application of Schöner's dynamic model of coupled levels of control.
Main Results:
- Stable head control precedes reaching onset by several weeks.
- Reaching onset involves muscle pattern reorganization for head and shoulder stabilization.
- Coordination of head, upper, and lower arm activity is critical for successful reaching.
Conclusions:
- Infant motor development prioritizes postural stability alongside reaching goals.
- Muscle pattern selection is influenced by individual factors like body size and energy.
- Motor development is a continuous interaction between the nervous system, body, and environment.
Abstract:
We conceptualize the coordinated development of posture and reaching within Schöner's (Ecological Psychology, 7:291-314, 1995) dynamic model of coupled levels of control: load, timing, and goal. In particular, the goal of postural stability must be maintained during a reach. Using longitudinal data from four infants followed from 3 weeks to 1 year, we show that coordination of the head with upper and lower arm activity is critical for successful reaching. First, infants acquire stable head control several weeks before reaching onset. Furthermore, reaching onset is characterized by a reorganization of muscle patterns to include more trapezius and deltoid activity, serving to stabilize the head and shoulder and provide a stable base from which to reach. We argue that initially, the system is working on postural stability and reaching as goals. Infants secondarily select appropriate muscle patterns to achieve those goals depending, in part, on their individual body sizes, body proportions and energy levels. Motor development proceeds as a continual dialogue between the nervous system, body, and environment.