According to a study published in the January 30 issue of the journal Nature Communications, we are exceptionally similar to our friends in how we perceive and respond to the world around us, and these similarities can be used to predict who our friends are.
Parkinson et al show evidence for neural homophily — neural responses when viewing audiovisual movies are exceptionally similar among friends, and that similarity decreases with increasing distance in a real-world social network. Image credit: Parkinson et al, doi: 10.1038/s41467-017-02722-7.
Dr. Carolyn Parkinson from the University of California, Los Angeles, and co-authors found that you can predict who people are friends with just by looking at how their brains respond to video clips.
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).
“Neural responses to dynamic, naturalistic stimuli, like videos, can give us a window into people’s unconstrained, spontaneous thought processes as they unfold,” Dr. Parkinson said.
“Our results suggest that friends process the world around them in exceptionally similar ways.”
The authors analyzed the friendships or social ties within a cohort of nearly 280 graduate students.
They 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 team 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 scientists 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,” said study senior author Dr. Thalia Wheatley, of Dartmouth College.
“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.”
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Carolyn Parkinson et al. 2018. Similar neural responses predict friendship. Nature Communications 9, article number: 332; doi: 10.1038/s41467-017-02722-7
