Visual experience affects handedness

Area of Science:

• Developmental psychology
• Neuroscience
• Human biology

Background:

• Early visual input influences the development of asymmetries in birds.
• Human handedness is thought to arise from a mix of genetic and environmental factors.

Purpose of the Study:

• To investigate if early visual experience, specifically through head posture, affects human handedness.
• To test the hypothesis that visual input during early development modulates lateral preferences.

Main Methods:

• Studied children with congenital muscular torticollis (a condition causing asymmetric head posture).
• Compared handedness, footedness, and eye-preference in torticollis patients versus control groups.
• Analyzed the relationship between head-tilt direction and the direction of functional asymmetries.

Main Results:

• Children with torticollis showed a higher probability of right- or left-handedness when their head-tilt favored increased visual experience of the contralateral hand.
• No significant relationship was found for footedness or eye-preference, though a non-significant trend aligned with handedness findings.

Conclusions:

• Early lateralized visual experience, influenced by head posture, appears to modulate human handedness.
• Findings support a combined gene-environment model for the development of handedness and potentially other lateral preferences.