Infants' tracking of objects and collections.

Recent research suggests that infants' understanding of the physical world is more complex and adult-like than previously believed. One of the most impressive discoveries has been infants' ability to reason about medium-sized, material objects. They are able to individuate objects in a scene, and to enumerate and reason about them. This article reports a series of experiments investigating 8-month-old infants' ability to reason about collections of objects. Experiment 1 shows a sharp contrast between infants' understanding of single objects versus collections. While infants detected the discontinuous ('Magical') disappearance of a single object, they did not detect the Magical Disappearance of a non-cohesive pile of objects. Experiments 2-4 found that infants' difficulty remained even when the distinct identity of each object in the collection was emphasized, but could be overcome if infants (a) first saw the individual objects clearly separated from each other prior to their being placed together in a pile, or (b) had prior experience with the objects making up the collection. Our findings suggest that infants' expectations about object behavior are highly specific regarding the entities they are applied to. They do not automatically apply to any and all portions of matter within the visual field. Both the behavior of an entity, and infants' prior experience play roles in determining whether infants will treat that entity as an object.