When do infants understand that they can obtain a desired part of a composite object by grasping another part?
When do infants start to understand that they can grasp an object by its handle when the interesting part is out of reach? Whereas it is known from preferential looking tasks that already at three months of age infants show surprise when all parts of an object do not move together, little is known about when infants are able to use such knowledge in an active grasp situation. To answer this question we presented six, eight, and 10 month-old infants in a cross-sectional and a longitudinal study with a white cardboard handle within reach and a bright ball at the end of the handle and out of reach. A trick condition, where the handle and the ball seem attached but were not, was added to get an indication of the infant's expectation by observing a possible surprise reaction. Results show that 6-month-olds' most frequent first behaviors consisted in pointing toward the ball without grasping the handle, or grasping the handle without looking at the ball until it moved. In addition, they often did not look surprised in the trick condition. Eight- and 10-month-olds most often grasped the handle while looking at the ball, and showed clear surprise in the trick condition. This was interpreted as showing that around eight or 10 months, infants take a significant step in understanding the cohesiveness of composite objects during grasping.
Laboratoire Psychologie de la Perception, UMR 8242, CNRS - Université Paris Descartes, Paris, France. Electronic address: jacqueline.fagard@parisdescartes.fr.
Jacqueline
J
Fagard
Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy.
Cecilia
C
Florean
Laboratoire Psychologie de la Perception, UMR 8242, CNRS - Université Paris Descartes, Paris, France.
Maja
M
Petkovic
Laboratoire Psychologie de la Perception, UMR 8242, CNRS - Université Paris Descartes, Paris, France.
Lauriane
L
Rat-Fischer
Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy.
Patrizia
P
Fattori
Laboratoire Psychologie de la Perception, UMR 8242, CNRS - Université Paris Descartes, Paris, France.
J Kevin
JK
O'Regan
D000375:Aging / Q000523:psychology; D002657:Child Development; D003430:Cross-Sectional Studies; D005260:Female; D005403:Fixation, Ocular; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D007223:Infant; D008137:Longitudinal Studies; D008297:Male; D009042:Motivation; D010775:Photic Stimulation; D011597:Psychomotor Performance; D014796:Visual Perception / Q000502:physiology*
Cohesiveness; Composite object; Development; Grasping; Infant