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Infants' Individuation of Rigid and Plastic Objects Based on Shape


Correspondence should be sent to Trix Cacchione, Department of Developmental Psychology, University of Zurich, Binzmuehlestrasse 14/21, CH-8050 Zurich, Switzerland. E-mail:


Recent research suggests that 12-month-old infants use shape to individuate the number of objects present in a scene. This study addressed the question of whether infants would also rely on shape when shape is only a temporary attribute of an object. Specifically, we investigated whether infants realize that shape changes reliably indicate identity changes only in the case of rigid objects, but not in the case of deformable plastic objects. Twelve-month-old infants observed how either a rigid or a plastic object was placed in a box. When searching the box, they retrieved either an object with the same (no-switch event) or with a different shape (switch event). Infants correctly inferred two distinct objects in the switch event in the case of rigid objects, but not in the case of plastic objects. A control experiment confirmed that this result was not due to a lack of salience of the shape transformation. Thus, infants' re-searching behavior indicated that they viewed shape as being diagnostic in the individuation process of rigid objects only.