Gazing into the eyes of a loved one, friend, or complete stranger is a natural instinct, and one brain scans can now prove. Researchers from the National Institute of Physiological Science (NIPS) took a closer look at what's going on inside the brain as one person gazes into the eyes of another. Their findings, published in the journal NeuroImage, provide unique insight into why eye contact is necessary to establish social interactions.

For the study, the research team examined the eyes of 96 participants who had never met before. Over the course of two days, participants sustained eye contact with one another during three different experiments. As they cast their gaze, researchers used a functional magnetic resonance imaging (fMRI) machine to monitor brain activity.

"We expected that eye-blink synchronization would be a sign of shared attention when performing a task requiring joint attention, and the shared attention would be retained as a social memory," explained the study’s co-author Takahiko Koike, a researcher at NIPS, in a press release.

Instead, participants began to blink in sync due to their mutual gaze, not because they were mimicking each other's activity. The fMRI scans revealed a region in the brain, called the right inferior frontal gyrus (IFG), lit up in response to direct eye contact. Once participants held one another's gaze, the IFG lit up at the same time and the brains synchronized, which suggests mutual eye contact is the key to developing social interactions.

Another recent study conducted by a research team from Leiden University in the Netherlands confirms the power eyes have when it comes to building trust. They found if two strangers stared into each other’s eyes as they dilated, they invested triple the amount of money compared to eyes that didn’t dilate. The mimic effect allowed people to foster a sense of trust through mutual eye contact. Once pupil size synchronized, their brains unconsciously built trust bonds, similar to the social memory the IFG created in the most recent study.

"Based on the enhancement of behavioral and neural synchronization during mutual gaze, we now know that shared attention is hard to establish without eye contact," Norihiro Sadato, senior author of the study, says. "Further investigation into the workings of eye contact may reveal the specific functional roles of neural synchronization between people."

Source: Sadato N and Koike T, et al. Neural substrates of shared attention as social memory: A hyperscanning functional magnetic resonance imaging study. NeuroImage. 2015.