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Updated: Aug 11, 2026
Frame-by-Frame Video Analysis of Idiosyncratic Reach-to-Grasp Movements in Humans
Published on: January 15, 2018
The coupling of head, reach and grasp movement in nine months old infant prehension
G Savelsbergh1, C von Hofsten, B Jonsson
1Institute for Fundamental and Clinical Human Movement Sciences, Amsterdam/Nijmegen Faculty of Human Movement Sciences, Vrije Universiteit, The Netherlands.
Insights
Nine-month-old infants struggle to adjust reaching movements when an object
Area of Science:
- Developmental psychology
- Motor control in infants
Background:
- Understanding infant motor development is crucial for identifying developmental milestones.
- Early reaching behavior provides insights into sensorimotor integration and adaptation.
Purpose of the Study:
- To investigate how 9-month-old infants adjust their reaching patterns in response to sudden object displacement.
- To examine the coordination between head and hand movements during perturbed reaches.
Main Methods:
- Infants were presented with a ball, and its position was suddenly altered mid-reach during perturbation trials.
- Movement time, grasp success, and kinematic data (head and hand latency, time to peak velocity) were recorded.
Main Results:
- Movement times doubled, and grasp success significantly decreased in perturbed trials compared to control trials.
- A strong correlation (0.78-0.85) was found between head and hand adjustment latencies, indicating tight coupling.
- Head movements initiated adjustments significantly earlier than hand movements, suggesting head-led control.
Conclusions:
- Infants require completion of an initial motor plan before redirecting a reach to a new target.
- Head and hand movements are tightly coupled during reaching, with the head anticipating and guiding the hand's adjustment.
Abstract:
In 9-month-old-infants adjustments in the reaching pattern to sudden changes in object location were examined. An attractive ball was presented to the infants at their midline and on some trials (perturbation trials) the ball suddenly changed position 15 cm to the right or left during the reach. For the perturbed trials the movement times approximately doubled compared to the control trials and significantly fewer balls were grasped. The results indicate that infants need to finish the first movement before being able to redirect the reach to a new destination. The correlation between the latency of the head and hand adjustment to the perturbation were 0.85 and 0.78 for movements to the left and to the right, respectively, indicating a tight coupling. The time between the start of the perturbation and peak velocity (TPPV) was significantly shorter for the head movement than for the hand movement, indicating that the head is leading the hand.
