Causality is in the eye of the beholder.

• Position: Cognition

We rely on our visual system more heavily than previously thought in determining the causality of events. A team of researchers has shown that, in making judgments about causality, we do not always need to use cognitive reasoning. In some cases, Our visual brain--the brain areas that process what the eyes sense--make these judgments rapidly and automatically, relates a study in Current Biology.

"Our study reveals that causality can be computed at an early level in the visual system; explains Martin Rolfs, who conducted much of the research as a post-doctoral fellow in New York University's Department of Psychology. "This finding ends a long-standing debate over how some visual events are processed: we show that our eyes can quickly make assessments about cause-and-effect--without the help of our cognitive systems."

We frequently make rapid judgments of causality ("The ball knocked the glass off the table"); animacy ("Look out; that thing is alive"), or intention ("He meant to help her"). These judgments are complex enough that many believe that substantial cognitive reasoning is required--we need our brains to tell us what our eyes have seen. However, some judgments are so rapid and effortless that they "feel" perceptual--we can make them using only our visual systems, with no thinking required.

It is not yet clear which judgments require significant cognitive processing and which may be mediated solely by our visual system. In this study, the researchers investigated one of these--causality judgments--in an effort to understand better the division of labor between visual and cognitive processes.

Their experiments centered on isolating how we perceive causality--i.e., where one event apparently triggers the next. The perception of causality generally involves two components, one that is stimulus based and one that is inference based. First, to see causal structure between two events, these events need to follow each other with little delay and typically require contact---for instance, a glass immediately falling Off a table after being knocked over. This is the stimulus-based...