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Correction processes in early reaching: reaches by infants to prismatically displaced targets
1Centre for Visual Sciences, Australian National University, Canberra City.
Insights
Six-month-old infants
Area of Science:
- Developmental Psychology
- Motor Control
- Infant Vision
Background:
- Early reaching movements in infants are crucial for sensorimotor development.
- Understanding visual-motor integration in infancy informs theories of cognitive development.
- Previous research established basic patterns of infant reaching.
Purpose of the Study:
- To investigate the role of visual guidance versus somatic feedback in shaping infant reaching trajectories.
- To determine how infants adjust their reaches in response to visual perturbations.
- To explore the developmental timeline of visual-motor control in 6-month-olds.
Main Methods:
- Infants aged 6 months performed reaching movements towards visual targets.
- Reaches were recorded under two conditions: no prism and lateral prismatic displacement.
- Movement trajectories were analyzed for deviations and adjustments.
Main Results:
- In the absence of prisms, infant reaches initially veered towards the target.
- With prisms, initial hand movements were unaffected, but later trajectory shifts occurred.
- These shifts suggest reliance on somatic feedback rather than continuous visual guidance for trajectory correction.
- Infants did approach the virtual target, indicating visual guidance during the approach phase.
Conclusions:
- Infant reaching trajectories are influenced by both visual and somatic feedback mechanisms.
- Somatic feedback appears critical for correcting reaching paths during the movement.
- Visual guidance is primarily active during the terminal phase of the reach in 6-month-olds.
Abstract:
A comparison was made between trajectories of reaches to visual targets by 6-months-old infants, with and without lateral prismatic displacement. In the No Prism condition, the major element of the movement veered towards the target, confirming the results of Mathew and Cook (1990). In the Prism condition, the prism did not affect hand position or movement direction at the beginning of the major element, but a lateral displacement was evident by the end of the element. This is taken as evidence that shifts in trajectory during the element were not due to visual guidance. It is suggested instead that these shifts may reflect correction based upon somatic feedback about position in relation to the visually specified goal of the movement. Evidence that the hand approached the virtual target supports the suggestion that any visual guidance was confined to the approach phase of the reach. Nevertheless, it appears that visual guidance was operating at this stage, since movement direction was displaced away from the virtual target and towards the real target.