Perceived causalities of physical events are influenced by social cues

In simple mechanical events, we can directly perceive causal interactions of the physical objects. Physical cues (especially spatiotemporal features of the display) are found to associate with causal perception. Here, we demonstrate that cues of a completely different domain--social cues--also impact the causal perception of physical events: The causally ambiguous events are more likely to be perceived as causal if the faces superimposed on the objects change from neutral to fearful. This effect has the following major properties: (a) The effect is caused by social information because it disappears when the faces are inverted or when the expression changes are unreasonable; (b) the social cues are integrated in a temporal window different from physical cues; and (c) the social cues impact the perception process rather than the decision process as the impact also appears in the causality-induced illusion. These findings suggest that the visual system relies on social information to infer the causal structure of the physical world.