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How Eye Contact Prepares the Brain to Connect

A new study reveals what happens when you look into someone else’s eyes.

When we make eye contact, we synchronize the blinking of our eyes.
Source: puhhha/iStock

Eye contact is special. It thrills us to gaze into a lover’s eyes. Parents know there is power in demanding that unruly children look at us when we’re speaking to them. Friends share knowing glances over inside jokes. These are very different scenarios, but they all require eye contact. Why? What makes eye contact special? This is not just a philosophical question. It’s a scientific one. And it’s the title of a paper just published by a team of Japanese scientists that reveals for the first time what happens in the brain in real time when two people look at each other. Intriguingly, this study also delivered more evidence of our hidden neural powers. Our brains can distinguish between live and delayed video clips of other people’s faces, even when we don’t consciously spot the difference.

Previous work has already shown that eye contact activates the social brain, the neural regions that orchestrate our responses to other people. Making eye contact signals to another person that you are paying attention. It is one way we share intention and emotion, and it requires that you synchronize eye movements with someone else.

The new study, published this week in eNeuro, deepens our understanding of just how eye contact prepares the social brain to empathize by revealing that it activates the same areas of each person’s brain simultaneously. Specifically, eye contact was shown to involve the cerebellum, which helps predict the sensory consequences of actions. And it triggers the limbic mirror system, a set of brain areas that are active both when we move any part of the body (including the eyes) and when we observe someone else doing the same. The limbic system, in general, underlies our ability to recognize and share emotion. In other words, it is critical to our capacity for empathy.

Until recently, the challenges of brain imaging have been such that scientists have only managed to study brain activity in one person at a time in functional magnetic resonance imaging machines (fMRI). But a cutting-edge technique called hyperscanning now makes it possible—in a few labs around the world, anyway—to put two people in separate fMRI machines simultaneously and have them communicate and see how their brains’ responses unfold.

The senior author of this paper, Norihiro Sadato of the National Institute for Physiological Sciences in Japan, first got interested in studying visual communication early in his career when he showed changes in the visual cortex of blind adults who learn to read Braille. He has now devoted decades to studying the neural underpinnings of social interaction.

For this study, Sadato and his colleagues put 16 pairs of adults in two MRI machines at the same time. None of the participants knew each other previously. Each scanner was equipped with both a video camera and a screen. Participants stared up at the screen showing the face of their partner. (The reason this can’t be done while people look directly at each other in person is that accurate brain imaging requires subjects to lie completely still within a very large machine.)

Sadato’s team used eye blinks as a marker of synchronization. “Eye blinks can provide social communication cues reflecting the internal state such as arousal, emotion and cognitive load, all of which affect the blink rate,” Sadato told me in an email. When eye blinks are synchronized, he added, “it reflects shared attention between participants.”

The team measured participants’ brains at rest, while they looked at a blank screen. And they showed each participant the video stream of his or her partner in two formats. One video was live, and the other introduced a 20-second delay. The participants were not told of the delay, and only one pair of participants noticed it. (That pair’s data was excluded). While looking into the other person’s eyes, participants were instructed to “think about their partner: What is he/she thinking about, what is his/her personality, how he/she is feeling?” They were also told not to laugh or grimace or make other explicit facial expressions.

There was a difference in the way that people’s brains responded to the live and delayed conditions. In the live condition versus the delayed condition, participants were more sensitive to their partner’s eye blinks. There was increased activation of the cerebellum and enhanced connectivity within the limbic mirror system. “Our findings suggest that perceptual-motor interaction occurs during eye contact without conscious awareness,” Sadato and colleagues wrote. Hyperscanning represents a considerable advance in that it allows the study of actual interaction rather than single participants, Sadato says.

These kinds of studies certainly make clear how much is communicated in . . . well, the blink of an eye.

Copyright: Lydia Denworth 2019.

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Koike, Takahiko et al. "What makes eye contact special? Neural substrates of on-line mutual eye-gaze: a hyperscanning fMRI study," eNeuro 2019; 10.1523.

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