Brain and Body Signals Synchronize with Eye Contact
Post by Anastasia Sares
The takeaway
The expression “being in sync” with another person is more true than we might think: both brain and body signals can start to synchronize when we make eye contact with someone—even more so if we are close with that person.
What's the science?
Most neuroimaging studies focus on what is happening in a single brain during some computer-based task. But humans are inherently social creatures, and likely respond much differently when face-to-face with another person. Enter hyperscanning: the method of scanning more than one brain at a time during a real interaction. This technique has been used to study musicians playing duets, parent-infant pairs, and more.
This week in Neurophontonics, Guglielmini and colleagues added physiological signals into a hyperscanning study, monitoring body signals like heart rate and blood pressure between people as they made eye contact.
How did they do it?
The experimental design was simple: seat two people across from each other at a table, first with eyes closed, and then with eyes open and making eye contact, for 10 minutes each. Some of these people knew each other well (siblings or couples), and others less well (colleagues or strangers). The authors used fNIRS (functional Near-Infrared Spectroscopy) to detect blood hemoglobin levels in the brain using infrared light, along with skin conductance, blood pressure, heart rate, etc. They broke down the signals into different frequency bands (fast oscillations, slow oscillations, very slow oscillations). They then lined up the signals for each pair of participants that had interacted to see how well the signals correlated in the eyes-closed versus eye-contact conditions. As a control condition, they compared the signals of people from different testing sessions who had not been paired.
What did they find?
The authors observed more synchronized blood flow in the brain (measured by total hemoglobin levels) during the eye-contact condition, while body temperatures were better synchronized in the eyes-closed condition. Signals from people who had been in the same testing session were more synchronized than the (control) signals of people who had been in different testing sessions. Most measures of synchronization were greater for people who knew each other well, like blood flow in the brain but also in heart rate and diastolic blood pressure. Skin temperature and electrical activity in the skin were also correlated with blood flow in the brain across people.
What's the impact?
This study demonstrates that eye contact results in significant changes in synchronization between individuals. Beyond that, it shows that it is possible to combine physiological data coming from the body with brain blood-flow measures in a hyperscanning experiment, expanding our ideas about what is possible with hyperscanning.
