True friends think alike: Brain scans can help scientists predict who your friends are

Scientists have apparently decoded the brain activity that can help them tell who your friends are. According to a new study, close friends have similar neural responses to real-world stimuli, and these similarities can be used to predict friendship.

In the study, published in the journal Nature Communications, the researchers said that it's possible to tell who your friends are by simply scanning your brains to find how they respond to video clips. As part of the research, scientists scanned the brains of different people and found that friends had the most similar neural activity patterns, followed by "friends-of-friends" and "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. Our results suggest that friends process the world around them in exceptionally similar ways," the study's lead author Carolyn Parkinson, a former postdoctoral fellow at Dartmouth College New Hampshire, and currently an assistant professor of psychology at the University of California, Los Angeles, said in a statement.

The researchers analysed the friendships or social ties of nearly 280 graduate students, and also estimated the social distance between pairs of individuals based on mutually reported social ties.

The researchers then asked 42 of the students to watch a range of videos while their neural activity was recorded using a fMRI scanner. The videos were related to a range of topics, including politics, science, comedy and music to ensure varied responses.

When the brain activities were compared across pairs of students, the researchers found that friends had the stronger neural response similarity than those further removed from each other in their social network. It was also revealed that neural pattern was common across brain regions involved in emotional responding, directing one's attention and high-level reasoning.

The similarity in neural activity among friends was still evident even when the researchers controlled for variables, including left-handed- or right-handedness, age, gender, ethnicity and nationality.

"These results suggest that we are exceptionally similar to our friends in how we perceive and respond to the world around us, which has implications for interpersonal influence and attraction," the researchers said in the study.

According to the researchers, their next step is to find whether people naturally get attracted towards others who perceive the world the same way and whether friends become more similar after they share their experiences.