title: Specialization of the motor system in infancy: from broad tuning to selectively specialized purposeful actions.
abstract: In executing purposeful actions, adults select sufficient and necessary limbs. But infants often move goal-irrelevant limbs, suggesting a developmental process of motor specialization. Two experiments with 9- and 12-month-olds revealed gradual decreases in extraneous movements in non-acting limbs during unimanual actions. In Experiment 1, 9-month-olds produced more extraneous movements in the non-acting hand/arm and feet/legs than 12-month-olds. In Experiment 2, analysis of the spatiotemporal dynamics of infants' movements revealed developmental declines in the spatiotemporal coupling of movements between acting and non-acting arms. We also showed that the degree of specialization in infants' unimanual actions is associated with individual differences in motor experience and visual attention, indicating the experience-dependent and broad functional nature of these developmental changes. Our study provides important new insights into motor development: as in cognitive domains, motor behaviours are initially broadly tuned to their goal, becoming progressively specialized during the first year of life.
authors.affiliation: Sensorimotor Development Research Unit, Department of Psychology, Goldsmiths, University of London, UK.
authors.forename: Hana
authors.initials: H
authors.lastname: D'Souza
authors.affiliation: Department of Psychology, University of Durham, UK.
authors.forename: Dorothy
authors.initials: D
authors.lastname: Cowie
authors.affiliation: Centre for Brain and Cognitive Development, Department of Psychological Sciences, Birkbeck, University of London, UK.
authors.forename: Annette
authors.initials: A
authors.lastname: Karmiloff-Smith
authors.affiliation: Sensorimotor Development Research Unit, Department of Psychology, Goldsmiths, University of London, UK.
authors.forename: Andrew J
authors.identifier: 0000-0002-4119-3748
authors.initials: AJ
authors.lastname: Bremner
mesh_terms: D002657:Child Development / Q000502:physiology*; D005121:Extremities / Q000502:physiology; D006801:Humans; D007223:Infant; D007858:Learning / Q000502:physiology; D009043:Motor Activity / Q000502:physiology*; D009068:Movement / Q000502:physiology; D011597:Psychomotor Performance