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A developmental transition in prehension modeled as a cusp catastrophe
R H Wimmers1, G J Savelsbergh, J van der Kamp
1Institute for Fundamental and Clinical Human Movement Sciences, Amsterdam/Nijmegen, The Netherlands.
Insights
Infant reaching and grasping transitions exhibit characteristics of a discontinuous phase transition, specifically a catastrophe. Arm weight and circumference significantly influence this developmental control.
Area of Science:
- Developmental psychology
- Motor control
- Dynamical systems theory
Background:
- Early infant motor development involves complex transitions.
- Understanding developmental changes as continuous or discontinuous is crucial.
- Catastrophe theory offers a framework for abrupt behavioral shifts.
Purpose of the Study:
- To model the developmental shift from reaching without grasping to reaching with grasping in infants.
- To determine if this motor milestone exhibits characteristics of a discontinuous phase transition (catastrophe).
Main Methods:
- A cross-sectional study of 58 infants aged 60-408 days.
- Infants reached for balls in a controlled setup, with reaches and grasps video-recorded.
- A cusp catastrophe model was statistically compared against linear and logistic regression models.
Main Results:
- The cusp catastrophe model provided a significantly better fit to the data than linear regression (p < .001).
- Akaike's Information Criterion indicated the cusp model outperformed the logistic model.
- Arm weight and arm circumference were identified as significant control parameters influencing the transition.
Conclusions:
- The developmental change in infant reaching and grasping aligns with a discontinuous phase transition model.
- Arm dimensions, specifically weight and circumference, play a key role in controlling this motor skill acquisition.
- Catastrophe theory provides a valuable lens for analyzing abrupt developmental changes in motor behavior.
Abstract:
The purpose of the study was to show that the change from reaching without grasping to reaching with grasping during the first 6 months of life carried the characteristics of a discontinuous phase transition (catastrophe). A cross-sectional study was carried out with 58 infants between 60 and 408 days old. The infants were seated in a specially designed seat, and presented with nine detachable balls on a black curved board within reaching distance at shoulder height. The number of reaches without and with grasping were scored from video. A cusp catastrophe model was fitted to the data. A Likelihood-Ratio test indicated that the likelihood of the cusp model was significantly higher, p < .001, than a linear regression model. The cusp model was also compared with a logistic model. Akaike's Information criterion for the cusp catastrophe exceeded the logistic model, thus indicating a general better fit. Based on prior research, the following potential control parameters were chosen: crown-heel length, total body weight, arm length, arm circumference, ponderal index, arm volume, arm weight, and body position relative to the horizontal. The cusp model predicted that arm weight and arm circumference significantly contributed to the control parameters. It was found that these two variables had their largest contribution to the asymmetry control parameters.