Development of Infant Handedness

University Of North Carolina Greensboro, Greensboro NC

Investigators

Abstract

Why are some people left-handed? Are there two (right- and non-right-handed), three (right-, left-, and mixed-handed) categories or is handedness a quantitative trait with relatively arbitrarily defined categories? With right-handedness dominating in the population, left-handedness and mixed handedness become atypical. Why, then, is atypical handedness associated with atypical hemispheric specialization for language and other psychological functions? Why is atypical handedness a marker for the development of various forms of socio-emotional and cognitive disorders? The proposed project provides crucial information about the early development of handedness that will help form the foundation for the finding answers to these questions. During the age of 6 to 14 months infants develop proficiency for apprehending objects, manipulating them, and employing complex bimanual manipulations (with action differences between the hands) that facilitate tool use, construction of artifacts, and solution to physical problems. Hand-use preferences for these skills appear during this period and play an important role in the distinction of what makes the actions skillful. The proposed project will chart the development of hand-use preferences for each of three manual skills (prehension, unimanual manipulation, and role differentiated bimanual manipulation), the relations among these skills, and their relation to the infant's age, neuromotor development, genotype and development of tool-use and object construction skills. Using a large sample and sophisticated quantitative techniques, different patterns in the development (as measured by age and/or neuromotor maturity) of lateralization of manual skill may be identified that can be compared to the infant's genotype, and tool-use and construction abilities.