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Postural and lateral asymmetries in the ontogeny of handedness during infancy
Insights
Newborns
Area of Science:
- Developmental neuroscience
- Human motor control
- Infant behavior
Background:
- Handedness, the preference for using one hand over the other, shows a strong dextral (right-hand) bias in humans.
- The developmental origins of this bias are not fully understood.
- Neonatal head-turning preference is a common observation in newborns.
Purpose of the Study:
- To investigate the relationship between neonatal head-turning preference and the development of hand-use preference in infants.
- To explore whether early head orientation influences the emergence of handedness.
Main Methods:
- Assessed hand-use preferences for reaching in 20 infants (10 rightward, 10 leftward head-turn preference) at 8 ages between 12-74 weeks postpartum.
- Monitored the stability of hand-use preferences over time.
- Observed the maintenance of neonatal head-turn preference and its effect on visual regard and motor control.
Main Results:
- Eighteen infants exhibited stable hand-use preferences throughout the study period.
- The direction of neonatal head-turn preference significantly predicted the infant's preferred hand.
- Neonatal head-turn preference persisted and induced lateral asymmetries in visual regard and hand motor control.
Conclusions:
- Neonatal head-turn preference is a significant predictor of infant hand-use preference.
- Early lateral asymmetries in visual and motor control, stemming from head-turning preference, likely contribute to the development of handedness.
- The prevalent rightward bias in handedness may originate, in part, from a rightward bias in neonatal head-turning preference.
Abstract:
Ten newborn infants who preferred to lie with their heads turned rightward and ten who preferred to lie with their heads turned leftward had their hand-use preferences for reaching assessed at 8 different ages during the period 12-74 weeks postpartum. Eighteen infants maintained stable hand-use preferences throughout this period and the direction of their neonatal head orientation preference predicted the hand they preferred to use. The neonatal head-turn preference was maintained through the first 2 months and induced lateral asymmetries in visual regard and motor control of the hands. These lateral asymmetries are plausible contributors to mechanisms linking neonatal headturn preference to infant hand-use preference. Thus, the dextral bias in handedness may be derived, in part, from the rightward bias in neonatal head-turn preference.