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INFANTS’ REPRESENTATION OF COLLECTIONS: “NOT AN OBJECT” OR “A NON-OBJECT INDIVIDUAL”?

Wen-Chi Chiang and Karen Wynn

Department of Psychology, University of Arizona, Tucson, AZ 85721, USA

Collections present a paradox. A collection of objects is not itself an object, and can violate the “object principles” identified by Spelke (e.g., 1994) -- it need not be cohesive or spatiotemporally continuous, for example (consider a flock of birds). Yet the individual members that make up such a collection are objects, subject to these very principles. We examine the issue of how infants represent and reason about such collections.

In several experiments by Chiang & Wynn (1997), infants showed no expectation that a collection would honor the principle of spatiotemporal continuity. In their Expt. 1, they showed 8 month-olds a pile of 5 small blocks, spread them out to show the individual objects, regrouped them, and pushed the pile behind a screen. Infants showed no surprise when the screen dropped to reveal nothing behind it. Their Expt. 4 obtained the same result, in which the blocks were moved one at a time after being spread out. One possible explanation is that infants may have initially misconstrued the pile as a single object; its subsequent dismantling, violating the object principle of cohesion, may thus have led infants to suspend the application of further object principles to the pile and its component pieces. Alternatively, infants may have represented the component parts as objects while simultaneously construing the whole collection as a non-object individual, but been unable to maintain both representations actively; the collective interpretation may have been more salient. Experiment 2 below teases apart these possibilities.

However, a methodological issue must first be addressed: Infants may simply have been unable to make sense of the experimental manipulations. They may have found confusing the visual transformation from pile (with a single visual contour evident) to line (with distinct contours for each block visible). Accordingly, our Exueriment 1 tests whether infants’ difficulty lies in an inability to follow the pile-to-line transformation, or instead results from their conceptual construal of the collection of objects. At the start of each trial, infants saw the 5 blocks lined up in a row so that their contours were distinct. The blocks were then piled together and spread back out (the “pile-to-line” transformation) and moved one at a time, either behind the screen (a “Magical Disappearance”) or out of the display (an ‘Expected Disappearance”). In both cases, the screen dropped to reveal an empty display behind it. In contrast to Chiang & Wynn (1997, Expt. 4), infants looked significantly longer at the Magical than the Expected disappearance B( 13) = 2.13, B c .03, one-tailed], showing that ( 1) they are not confused by the “pile-to-line” transformation, and suggesting that (2) an initial perception of the distinct contours of the 5 blocks facilitates an “object” construal of each of the blocks.

In Exwriment (currently underway), just prior to the experiment proper and in a separate room, each infant is presented with a pile of 5 blocks used and encouraged to manipulate them. Next, infants are presented with alternating test events showing Expected and Unexpected disappearances of a collection of objects which was initially piled together and subsequently moved as a whole as in Chiang & Wynn (1997, Expt. 1). If infants previously failed because they did not construe the component parts as objects (as might occur if they construed the pile as a non-solid substance), this experience should help them to represent the pile as being composed of distinct objects. However, if infants failed previously because the experimental manipulations focused them on the collection itself as a non-object individual, even though they represented the component parts as objects, then this experience should not alter their performance as the experimental manipulations are the same as Chiang & Wynn’s.