title: Right-left approach and reaching arm movements of 4-month infants in free and constrained conditions.
abstract: Recent theories on the evolution of language (e.g. Corballis, 2009) emphazise the interest of early manifestations of manual laterality and manual specialization in human infants. In the present study, left- and right-hand movements towards a midline object were observed in 24 infants aged 4months in a constrained condition, in which the hands were maintained closed, and in a free condition. A left-hand dominance for approach movements without contact with the object, and a right-hand dominance for reaching movements with object contact was observed in the free condition. In the constrained condition reaching movements of the right hand decreased dramatically. These results are interpreted as strong evidence of manual specialization in 4-month olds, with approach movements having a localization role and reaching movements announcing future right-hand dominance for prehension and object manipulation.
authors.affiliation: Psychology and Cognitive Neurosciences, CNRS UMR 8189, University Paris Descartes, Institut de Psychologie, 71 Avenue Edouard Vaillant, 92774 Boulogne-Billancourt Cedex, France. francoise.morange-majoux@parisdescartes.fr
authors.forename: Françoise
authors.initials: F
authors.lastname: Morange-Majoux
authors.forename: Georges
authors.initials: G
authors.lastname: Dellatolas
mesh_terms: D000704:Analysis of Variance; D001132:Arm; D002657:Child Development / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007223:Infant; D008297:Male; D009048:Motor Skills / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D012016:Reference Values; D012149:Restraint, Physical; D013028:Space Perception / Q000502:physiology*