Parametric animacy percept evoked by a single moving dot mimicking natural stimuli.

Identifying moving things in the environment is a priority for animals as these could be prey, predators, or mates. When the shape of a moving object is hard to see, motion becomes an important cue to distinguish animate from inanimate things. We report a new stimulus in which a single moving dot evokes a reasonably strong percept of animacy by mimicking the motion of naturally occurring stimuli, with minimal context information. Stimulus movements are controlled by an equation such that changes in a single movement parameter lead to gradual changes in animacy judgments with minimal changes in low-level stimulus properties. An infinite number of stimuli can be created between the animate and inanimate extremes. A series of experiments confirm the strength of the percept and show that observers tend to follow the stimulus with their eye gaze. However, eye movements are not necessary for perceptual judgments, as forced fixation on the display center only slightly reduces the amplitude of percept changes. Withdrawing attentional resources from the animacy judgment using a simultaneous secondary task further reduces percept amplitudes without abolishing them. This stimulus could open new avenues for the principled study of animacy judgments based on object motion only.