Abstract
Visual motion contributes to high-level percepts such as animacy perception, such as that a target dot is perceived as animate when it moves along a random trajectory. It has been shown that perceived animacy of a target was weakened when task-irrelevant surrounding dots exhibited synchronous motion with the target. We examined the underlying mechanism of the modulating effect of synchronous motion by analyzing eye movements with a hidden Markov model (HMM) based approach that summarized both participant’s regions of interests and scan paths. Participants were asked to rate the perceived animacy of a moving red target dot among other white dots that either had synchronous motion with the target or not. Results showed that the perceived animacy of the target was impaired by synchronous motion, consistent with previous studies. Furthermore, by clustering participants’ HMMs, we showed that participants’ eye fixations were initially on the target and then shifted to the surrounding dots during the task. However, participants were more likely to shift eye fixations back to the target when the surrounding dots exhibited synchronous motion as compared to when the surrounding dots did not exhibit synchronous motion. Taken together, our results showed that synchronous motion impaired the perceived animacy by inducing involuntary shifts of eye fixations back to the target. Higher perceived animacy can be inferred without subjective reports by viewing the spatial-temporal eye-movement patterns and seeing that observers are more inclined to explore the interaction between the target and the surrounding dots due to the random motion trajectory.