Perceptual animacy: visual search for chasing objects among distractors.

Anthropomorphic interactions such as chasing are an important cue to perceptual animacy. A recent study showed that the detection of interacting (e.g., chasing) stimuli follows the regularities of a serial visual search. In the present set of experiments, we explore several variants of the chasing detection paradigm in order to investigate how human observers recognize chasing objects among distractors although there are no distinctive visual features attached to individual objects. Our results indicate that even a spatially separated presentation of potentially chasing pairs of objects requires attention at least for object selection (Experiment 1). In the chasing detection framework, a chase among nonchases is easier to find than a nonchase among chases, suggesting that cues indicating the presence of a chase prevail during chasing detection (Experiment 2). Spatial proximity is one of these cues toward the presence of a chase because decreasing the distance between chasing objects leads to shorter detection latencies (Experiment 3). Finally, our results indicate that single objects provide the basis of chasing detection rather than pairs of objects. Participants would rather search for one object that is approaching any other object in the display than for a pair of objects involved in a chase (Experiments 4 and 5). Taken together, these results suggest that participants recognize a chase by detecting one object that is approaching any of the other objects in the display.