From the reaching behavior at 5 months of age to hand preference at preschool age

Area of Science:

• Developmental Psychology
• Neuroscience
• Motor Control

Background:

• Manual laterality, the preference for using one hand over the other, is a hallmark of human motor development.
• Understanding the early predictors of established handedness is crucial for developmental research.
• Infant reaching behavior provides a window into emerging motor asymmetries.

Purpose of the Study:

• To investigate infant reaching patterns at 5 months of age.
• To determine the relationship between early hand use and manual laterality in preschool children.
• To explore the influence of object placement (midline, right, or left hemispace) on infant reaching behavior.

Main Methods:

• Longitudinal study of 20 infants (13 female, 7 male).
• Assessment of reaching hand preference at 5 months for objects in different spatial locations.
• Assessment of manual laterality across 22 motor tasks at 5 years and 7 months of age.
• Calculation of handedness status along a sinistrality-dextrality continuum.

Main Results:

• Most infants (all but one) exhibited unimanual reaching at 5 months.
• Reaching preference was primarily influenced by spatial location, not object type.
• Infants with consistent right-hand use for right-sided objects at 5 months showed significantly greater right-hand laterality later in preschool (p < .05).
• Infants using their left hand for left-sided objects at 5 months demonstrated less right-hand lateralization approximately 5 years later (p < .05).

Conclusions:

• Early-emerging, space-dependent reaching patterns in infancy are predictive of later manual laterality.
• Consistent, spatially-biased hand use in early infancy may establish foundational pathways for established handedness.
• The findings highlight the importance of early sensorimotor experiences in shaping long-term motor asymmetries.