Brain’s tracking system uses 'ensemble coding' to follow crowd’s gaze

Even without the introductory “Look!,” psychology says you’d still be able to pick up that flying high above was not, in fact, a bird or a plane but Superman himself. Our brains have evolved the uncanny ability to track people’s gazes, and new research says the more people, the merrier.

Almost instinctually, if a group of people turns its collective gaze in one direction, you’ll follow suit. Why? Psychologists call it “ensemble coding.” Much in the same way you see a tree as a solid object, rather than a dense network of branches and leaves, your brain sees a crowd of people (an ensemble) and processes it (coding) as one unit. One person turns to look over your shoulder, and you don’t bat an eye. Twenty people look over your shoulder, and you’d better turn around.

According to psychology researcher Timothy Sweeny, of the University of Denver, “this highlights the importance of group behavior in human experience.” The notion of a “group” is so fundamental to our flourishing as a species “that we have, in fact, evolved dedicated brain processes to perceive them,” he said in a press release.

Sweeny and his co-researcher David Whitney, from the University of California, Berkeley, wanted to learn more about ensemble coding and what sort of visual “gist” people get when they look at crowds. They had people look at a crowd of 16 computer-generated faces and asked them, after showing the crowd for only a fifth of a second, where they thought the crowd was looking. Sometimes people looked at four people at a time, others only one or two, Medical Daily reports.

There wasn’t enough time, Sweeny and Whitney explain, for participants to look at each crowd member’s gaze individually. To answer correctly, they had to get the gist of the gaze. And with each added face in the crowd, the researchers found their hypothesis proved truer. Ensemble coding improved, which meant gaze-tracking improved.   

“Even though there wasn’t enough time to inspect the individuals, the participants were still able to see the gist of what the entire crowd was doing, as a group,” Sweeny said.

In terms of clinical significance, the team believes the greatest benefactor is autism research. Part of the difficulty found in children with autism spectrum disorder (ASD) is getting them to respond correctly to social cues. Kids with ASD frequently miss when their peers express emotion, and physical gestures that would otherwise be obvious go unnoticed.

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