This article contrasts intuitive knowledge about projectile motion expressed in action with knowledge expressed in explicit judgments. In the action condition of Experiment 1 children and adults threw a ball horizontally from different heights to hit targets on the floor; in the judgment condition the same subjects rated the respective launch speeds required. All age groups appropriately varied the launch speed with respect to both height of release and target distance in the action condition. In the judgment condition, however, kindergartners failed to integrate the relevant dimensions and even fourth graders and adults showed misconceptions of the speed-height relation. Experiment 2 established that the speed gradations in the action condition did not critically depend on visual flight feedback or the availability of outcome information. We conclude that perceptual-motor knowledge about projectile motion is distinct from naive, verbal-cognitive concepts of projectile motion and follows different developmental courses.

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Using looking-time measures, the authors examined untrained chimpanzees' (Pan troglodytes) ability to distinguish between adequate and inadequate support. In 3 experiments, the chimpanzees' sensitivity to different support relations between 2 objects was assessed. In each experiment, the chimpanzees saw a possible and an impossible test event, presented as digital video clips. Looking times in the 3 experiments suggest that chimpanzees use amount of contact between 2 objects, but not type of contact, to distinguish between adequate and inadequate support relations. These results indicate that chimpanzees have some intuition about support phenomena but their sensitivity to relational object properties may differ from that of human infants (Homo sapiens) in this domain.