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Online reach correction in 6- and 11-month-old infants
Erik Verhaar1, W Pieter Medendorp1, Sabine Hunnius1
1Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, The Netherlands.
Insights
Infants develop online reach control early in life. Six- and 11-month-olds adjusted their arm movements toward a moving toy, showing developing motor control and replanning abilities.
Area of Science:
- Developmental psychology
- Motor control research
- Infant motor development
Background:
- Understanding how infants control their movements is crucial for developmental research.
- Online reach control allows for real-time adjustments to reaching movements.
- Previous research has explored infant reaching, but the developmental trajectory of online correction is less understood.
Purpose of the Study:
- To investigate the developmental changes in online reach control in infants.
- To determine the age at which infants can make rapid, online adjustments to their reaching movements.
- To characterize the nature of reach correction in 6- and 11-month-old infants.
Main Methods:
- Tracking the hand position of 6- and 11-month-old infants as they reached for a toy.
- Introducing unexpected displacements of the toy during the reaching movement (perturbation trials).
- Comparing perturbed reaches to baseline reaches using autoregression analysis to quantify online correction.
Main Results:
- Infants in both age groups successfully adjusted their reach trajectories in response to the toy's displacement.
- Eleven-month-old infants corrected their reach within a single movement unit.
- Six-month-old infants' corrections spanned multiple movement units, indicating a less refined control mechanism.
Conclusions:
- Infants possess a basic capacity for online reach control by 6 months of age.
- The ability to refine ongoing reaches develops significantly between 6 and 11 months.
- This study highlights the maturation of the infant reach control system and its sophisticated online adaptation capabilities.
Abstract:
The current study investigated the development of online reach control. Six- and 11-month-old infants reached for a toy while their hand position was tracked. The toy either remained stationary (baseline trials) or unexpectedly displaced left- or rightward during the reach (perturbation trials). To obtain a measure of online reach correction, we compared reaches in the perturbation trials to reaches in baseline trials using autoregression analysis. Infants of both age groups adjusted their reach trajectories in the direction of the displacement. Moreover, we divided the reaching movements into movement units, defined as the submovements of a reach between local minima in hand speed. Eleven-month-old infants adjusted their reach within the span of a single movement unit; corrections in 6-month-olds spanned multiple movement units. These results suggest that the reach control system has a rudimentary replanning capacity by 6 months of age, which, with age, further develops to a more sophisticated online control mechanism for ongoing reaches.
