Infants' use of motion cues in object individuation processes.

We investigated 10-month-old infants' and adults' numerical expectations in scenarios where information on self-motion and static object features may give rise to numerically incongruent representations. A red circle or a blue box with yellow stripes appeared on the left side of a screen, moved autonomously sideways and then moved back behind the screen. Next, on the opposite side, an identical object was first brought in view by a hand and then pushed back behind the screen (Experiments 1 and 2). The screen was finally removed, revealing either one or two objects. Infants looked longer at one-object test events, suggesting that they expected to find two objects. Adults were also shown these animations and were asked for their numerical expectations. Contrary to infants, they expected one single object (Experiment 3). Whereas preverbal infants' numerical expectations appeared to be dominated by information on object autonomous and induced motion, adults' expectations were mainly guided by information about object shape, size, and color. These findings were discussed in relation to current models on the development of object individuation processes.