title: Infant exploratory learning: influence on leg joint coordination.
abstract: A critical issue in the study of infant development is to identify the processes by which task-specific action emerges from spontaneous movement. Emergent leg action has been studied by providing contingent reinforcement to specific leg movements using an overhead infant-activated mobile, however, there is limited information on the strategies used by infants to support the emergence of task-specific leg action from spontaneous movement. The purpose of this study is to (1) determine the ability of 3 month old infants to learn, through discovery, the contingency between leg action and mobile activation using a virtual threshold, and (2) identify strategies, defined by variance of the end-effectors (feet) and hip-knee joint coordination, used by infants that learned the contingency. Fourteen 3 month old infants participated in 2 sessions of mobile reinforcement on consecutive days. As a group, infants increased the percentage of mobile activation to meet performance criteria on Day 2, but did not meet memory or learning criteria across days. However, five infants learned the contingency based on individual learning criteria. When interacting with the mobile on Day 2 as compared to spontaneous kicking on Day 1, infants who learned the contingency, but not infants who did not learn the contingency, increased variance of the end-effectors (feet) in the vertical, task-specific direction and demonstrated less in-phase hip-knee joint coordination. An important discovery is that infants can discover this very specific contingency, suggesting that this movement behavior (action) can be shaped in future work. This may have implications for the rehabilitation of infants with atypical leg action.
authors.affiliation: Division of Biokinesiology & Physical Therapy, University of Southern California, Los Angeles, California, United States of America.
authors.forename: Barbara
authors.initials: B
authors.lastname: Sargent
authors.affiliation: Division of Biokinesiology & Physical Therapy, with Joint Appointments in the Neuroscience and Computer Science Departments, University of Southern California, Los Angeles, California, United States of America.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Schweighofer
authors.affiliation: Department of Physical Therapy, Niigata University of Health and Welfare, Niigata, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Kubo
authors.affiliation: Division of Biokinesiology & Physical Therapy, Department of Pediatrics, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America.
authors.forename: Linda
authors.initials: L
authors.lastname: Fetters
mesh_terms: D002657:Child Development / Q000502:physiology; D005106:Exploratory Behavior / Q000502:physiology*; D005260:Female; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D007223:Infant; D007719:Knee Joint / Q000502:physiology; D007858:Learning / Q000502:physiology*; D007866:Leg / Q000502:physiology*; D008297:Male; D008568:Memory / Q000502:physiology; D009068:Movement / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D012054:Reinforcement, Psychology; D013997:Time Factors