Understanding projectile acceleration

Throwing and catching balls or other objects is a generally highly practice d skill; however, conceptual as well as perceptual understanding of the mec hanics that underlie this skill is surprisingly poor. In 5 experiments, we investigated conceptual and perceptual understanding of simple ballistic mo tion. Paper-and-pencil tests revealed that up to half of all participants m istakenly believed that a ball would continue to accelerate after it left t he thrower's hand. Observers also showed a remarkable tolerance for anomalo us trajectory shapes. Perceptual judgments based on graphics animations rep licated these erroneous beliefs for shallow release angles. Observers' tole rance for anomalies tended to decrease with their distance from the actor. The findings are at odds with claims of the naive physics literature that l iken intuitive understanding to Aristotelian or medieval physics theories. Instead, observers seem to project their intentions to the ball itself (ext ernalization) or even feel that they have power over the ball when it is st ill close.