Abstract

The origin in infancy of the distinction between animate beings (animals and humans), and inanimate objects (vehicles, furniture, etc.) is a research topic of theoretical and empirical interest. One recent proposal is that infants form concepts of animate beings and inanimate objects on the basis of motion cues. In the present experiments, infants' ability to associate motion cues with animals and vehicles was tested. The motion cues of line of motion trajectory and type of motion onset were tested in four experiments. Line of motion trajectory was depicted using bouncing as the inanimate trajectory and jumping as the animate trajectory. Type of motion onset was depicted using externally caused motion onset as the inanimate onset and self-initiated motion onset as the animate onset. In each experiment, infants were presented with animated events using an infant-controlled habituation procedure. In the habituation phase, infants saw an animal performing an animate motion cue and a vehicle performing an inanimate motion cue. In the test phase, the habituation-phase pairing of category and motion cue was maintained in one event and broken in the other event. In Experiment 1, 12-, 16-, and 20-month-olds were tested on their ability to associate trajectory and object kind under stringent conditions in which the animals' legs' and the vehicles' wheels did not move. Only 20-month-olds showed a robust ability to associate trajectory and category. In Experiment 2, 16-month-olds' ability to associate trajectory and category was not facilitated by more ecologically valid events in which the animals' legs and the vehicles' wheels moved and the animate features of the jumping trajectory were increased. In Experiment 3, 16-month-olds did not associate motion onsets and category. In Experiment 4, 16-month-olds were unable to associate these particular motion onsets with individual animals and vehicles, suggesting that infants were unable to discriminate between these particular types of motion onset. The present research indicates infants are able to associate trajectory with animals and vehicles by 20 months. Directions for future research are discussed, including techniques for further examining the integration of motion into infants' concepts.