Infants' ability to associate different motion trajectories with animals and vehicles

Researchers have postulated that infants use motion cues (e.g., line of trajectory) to distinguish between animate and inanimate objects. However, little empirical research has addressed whether infants associate particular motion cues with object kinds. The present study examined infants' ability to associate jumping over an obstacle with animals, and hitting an obstacle and rebounding with vehicles. An infant-controlled habituation procedure was used. Sixteen- and 20-month-old infants were habituated to two category-congruent motion events: an animal jumping over a wall and a vehicle hitting a wall and rebounding backwards. During the habituation events, a stationary animal or vehicle was placed on one side of the screen to control for novelty effect of the exemplar in the test events (e.g., if an animal was jumping over the wall, then a vehicle was stationary). Subsequently, infants were presented with two test events. In the congruent test event, the stationary animal or vehicle from the habituation events engaged in the expected motion (i.e., animal jumping or vehicle rebounding). In the incongruent event, the stationary animal or vehicle from the habituation events violated the expected motion path (i.e., an animal rebounding or a vehicle jumping). The results revealed that by 16 months of age, infants can associate different lines of trajectory with different object kinds, and are surprised when this association is violated. The results are discussed in the context of the recent developmental literature, and infants' conceptualization of animates and inanimates