The Relation of Unimanual and Bimanual Reaching to Crossing the Midline

• Published in: Child development Vol. 73; no. 5; pp. 1353 - 1362
• Main Authors: Van Hof, P., Van Der Kamp, J., Savelsbergh, G.J.P.
• Format: Journal Article
• Language: English
• Published: Boston, USA and Oxford, UK Blackwell Publishers Inc 01-09-2002; Blackwell Publishers; Blackwell; Blackwell Publishing Ltd
• Subjects: Arm; Babies; Behavioral neuroscience; Biobehavioral Development, Perception, and Action; Biological and medical sciences; Brain - physiology; Cameras; Case studies; Child development; Children; Development; Developmental psychology; Developmental Stages; Eye Hand Coordination; Functional Laterality - physiology; Fundamental and applied biological sciences. Psychology; Hand - physiology; Hands; Humans; Infancy; Infant; Infants; Learning; Learning - physiology; Motor ability; Motor Development; Movement - physiology; Newborn. Infant; Object Manipulation; Posture - physiology; Prehension; Psychology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Reaching; Reaching Behavior; Videotape Recording; Young Children; Human; Psychomotor development; Follow up study; Goal directed movement; Infant; Manual activity; Bimanual activity; Motricity
• ISSN: 0009-3920; 1467-8624
• DOI: 10.1111/1467-8624.00476

The present study assessed the development of reaching for objects positioned in front of the contralateral shoulder. In particular, it examined how the development of crossing the midline is related to the development of bimanual reaching. Twenty infants were observed longitudinally at 12,18, and 26 weeks of age while reaching for two balls (3 cm and 8 cm in diameter) located at three positions (ispsilateral, midline, and contralateral). The reaches were analyzed from video recordings. With age, the infants increasingly adapted the number of hands used to the size of the object. The number of reaches crossing the body midline increased with age. Furthermore, the majority of the midline crossings were part of two-handed reaches for the large ball and occurred at or after onset of bimanual reaching. Together, these findings strongly suggest that the development of crossing the body midline emerges in the context of bimanual reaching. It was concluded that the need to grasp a large ball positioned contralaterally with two hands induces midline crossing. Hence, the development of midline crossings is not exclusively dependent on organismic constraints (e.g., the maturation of hemispheric connections), but rather on their interaction with environmental constraints (e.g., object size).