Friends have similar neural responses to real-world stimuli and these similarities can be used to predict who your friends may be, according to a Dartmouth study. The study suggests that since you perceive the world the way your friends do, it is possible to predict friends with just by looking at how your brains respond to video clips.
The research team found that you can friends had the most similar neural activity patterns, followed by friends-of-friends who, in turn, had more similar neural activity than people three degrees removed (friends-of-friends-of-friends).
Published in Nature Communications, the study is the first of its kind to examine the connections between the neural activity of people within a real-world social network, as they responded to real-world stimuli, which in this case was watching the same set of videos.
The study analyzed the friendships or social ties within a cohort of nearly 280 graduate students. The researchers estimated the social distance between pairs of individuals based on mutually reported social ties. Forty-two of the students were asked to watch a range of videos while their neural activity was recorded in a functional magnetic resonance imaging (fMRI) scanner. The videos spanned a range of topics and genres, including politics, science, comedy and music videos, for which a range of responses was expected. Each participant watched the same videos in the same order, with the same instructions. The researchers then compared the neural responses pairwise across the set of students to determine if pairs of students who were friends had more similar brain activity than pairs further removed from each other in their social network.
The findings revealed that neural response similarity was strongest among friends, and this pattern appeared to manifest across brain regions involved in emotional responding, directing one's attention and high-level reasoning. Even when the researchers controlled for variables, including left-handed- or right-handedness, age, gender, ethnicity, and nationality, the similarity in neural activity among friends was still evident. The team also found that fMRI response similarities could be used to predict not only if a pair were friends but also the social distance between the two.
"We are a social species and live our lives connected to everybody else. If we want to understand how the human brain works, then we need to understand how brains work in combination-- how minds shape each other," explains senior author Thalia Wheatley, an associate professor of psychological and brain sciences at Dartmouth, and principal investigator of the Dartmouth Social Systems Laboratory.
For the study, the researchers were building on their earlier work, which found that as soon as you see someone you know, your brain immediately tells you how important or influential they are and the position they hold in your social network.
The research team plans to explore if we naturally gravitate toward people who see the world the same way we do, if we become more similar once we share experiences or if both dynamics reinforce each other.