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Infant Sitting and Multi-Directional Reaching Skill
Jaya Rachwani1, Victor Santamaria2, Xupeng Ai3
1Department of Physical Therapy, Hunter College, City University of New York, New York, New York, USA.
Insights
Infants can reach and grasp toys in multiple directions even when they are new to sitting. Sitting experience improves posture but not reaching ability, suggesting trunk and arm stability are key for learning to sit.
Area of Science:
- Developmental science
- Motor control
- Infant behavior
Background:
- Infants develop sitting ability between 6 and 10 months.
- Reaching is a crucial motor skill for infant development.
- Understanding reaching in unsupported sitting informs developmental milestones.
Purpose of the Study:
- To investigate the functionality of multi-directional reaching in infants.
- To examine the influence of sitting experience on reaching and postural stability.
- To analyze kinematic differences in reaching based on direction and experience.
Main Methods:
- Tested 21 infants (6-10 months) with varying sitting experience.
- Recorded reaching tasks (forward, rightward) during unsupported sitting.
- Utilized behavioral and machine learning-based kinematic analyses.
Main Results:
- All infants successfully reached and grasped toys in both directions.
- Infant falls and postural support adjustments were minimal.
- Greater sitting experience correlated with improved upright posture.
- No significant differences in trunk displacement or reaching kinematics were found based on direction or experience.
Conclusions:
- Multi-directional reaching is a functional skill for infants regardless of sitting experience.
- Trunk and arm stability in sagittal and frontal planes are fundamental for acquiring sitting skills.
- Early sitting development supports the emergence of complex motor behaviors like reaching.
Abstract:
We tested twenty-one 6- to 10-month-old infants with a wide range of sitting experience in forward and rightward reaching during unsupported sitting on the floor. Sessions were video-recorded for further behavioral and machine learning-based kinematic analyses. All infants, including novice sitters, successfully touched and grasped toys in both directions. Infant falls, hand support, and base of support changes were rare. Infants with more sitting experience showed better upright posture than novice sitters. However, we found no differences in trunk displacement or reaching kinematics between directions or across sitting experience. Thus, multi-directional reaching is functional in both novice and experienced infant sitters. We suggest that trunk and arm stability in sagittal and frontal planes is integral to learning to sit.
