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Age-related changes in reaching behavior
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AGE-RELATED CHANGES IN REACHING BEHAVIOR
Barbara Morrongiello & Patrick Rocca U. of Western Ontario, London Ont., N6A 5C2 This study examined the ap peoach and contact lilases of reaching and doctments changes in visual-motor coordination follCMing the onset of visually-guided reaching at 4 months. Infants 5, 7, and 9 months were videorecorded while reaching for a rod in a horizontal (H) or vertical (V) orientation and for a rod that changed orientation after the start of So reach (H to V, or V to H). There was an increase with age in one-handed reaches; by 9 months nearly all reaches were of this type. Further, 5-month-olds reached equally often with the right and left hand, but 7- and 9-month-olds preferred the right hand. The appeoaeh path at 5 months was a circular swipe-type motion, whereas by 9 months infants efficiently directed their hand perpendicular to the rod. Grasping on contact never occurred at 5 months, whereas by 9 months this occurred 50% of the time. The incidence of grasps follCMing contact, which reflects the use of nOll'lisual information, was 30% and did not vary with age. There were no age differences in the incidence of contacting the stationary rod. Hcwever, on change-orientation trials, 5-month-olds l reaching was severely disrupted. Older infants used visual feedback and adjusted their hand for contact, with 9-month-olds surpassing 7-month-olds in competence, primarily in the efficiency with which they contacted the rod.
AGE-RELATED CHANGES IN REACHING BEHAVIOR
Barbara Morrongiello & Patrick Rocca U. of Western Ontario, London Ont., N6A 5C2 This study examined the ap peoach and contact lilases of reaching and doctments changes in visual-motor coordination follCMing the onset of visually-guided reaching at 4 months. Infants 5, 7, and 9 months were videorecorded while reaching for a rod in a horizontal (H) or vertical (V) orientation and for a rod that changed orientation after the start of So reach (H to V, or V to H). There was an increase with age in one-handed reaches; by 9 months nearly all reaches were of this type. Further, 5-month-olds reached equally often with the right and left hand, but 7- and 9-month-olds preferred the right hand. The appeoaeh path at 5 months was a circular swipe-type motion, whereas by 9 months infants efficiently directed their hand perpendicular to the rod. Grasping on contact never occurred at 5 months, whereas by 9 months this occurred 50% of the time. The incidence of grasps follCMing contact, which reflects the use of nOll'lisual information, was 30% and did not vary with age. There were no age differences in the incidence of contacting the stationary rod. Hcwever, on change-orientation trials, 5-month-olds l reaching was severely disrupted. Older infants used visual feedback and adjusted their hand for contact, with 9-month-olds surpassing 7-month-olds in competence, primarily in the efficiency with which they contacted the rod.