(Washington Post illustration; iStock)


About the easiest action you can take in social media is to "like" a tweet or a photo.

If you're a teenager, your brain is particularly primed to "like" what others have "liked," according to researchers from UCLA.

Their new study, published in Psychological Science, is thought to be the first to replicate the social media experience while people are inside an fMRI scanner. The findings underscore the importance of both reward-seeking behavior and peer acceptance in adolescence.

Thirty-four adolescents, ages 13-18, roughly equal numbers male and female, participated in the experiment. All were shown images from Instagram: a mixture of neutral pictures and those depicting "risky" behaviors, such as smoking marijuana, making rude gestures and wearing skimpy clothing. For each image, the subjects had to decide whether to "like" it. They were asked to respond as if they were on their own social media accounts.

(Courtesy of UCLA)

The Instagram images also included the number of "likes" from other people, but unbeknownst to the subjects, each image's number of "likes," which varied from 0 to 43, was assigned by the researchers. That number, it turns out, made all the difference: The higher the number of "likes," the more willing the subject was to "like" it as well. This held true even for images that portrayed risky behaviors.

"We found that the popularity of a photo had a significant effect on the way that photo was perceived," the authors wrote.

One of the brain structures activated in subjects who viewed the most popular photos was the nucleus accumbens, which is involved in explicit pleasure, such as eating chocolate.

"It’s involved in reinforcement learning," said lead author Lauren Sherman. "Whether that’s 'likes' or money, it will likely influence your behavior in the future. We also know it’s very sensitive in adolescents, and this may be one of the reasons social media is so popular, because teens are so primed for this pleasurable experience."

The most popular photos also activated brain regions involved in social cognition, social memories, reward and imitation. Even the areas of the brain that specialize in vision were more active if the photos had more "likes," suggesting to Sherman and her colleagues that "the way they scanned them, taking in the information, changed with the knowledge that the photos were popular."

"There's something special about the brain that is uniquely attuned to the social sphere," she added. "If you’re a human in any culture you need to learn about your social world, and it will be unique to your circumstances. ... It's  possible that the 'likes' are cues that are orienting [the adolescents] to what is important."

Scientists have shown in recent years that the brain of an adolescent is only 80 percent developed, a process that can take a person into his or her 30s to complete.

During these teen years, said Sherman, "they’re learning what’s cool and what’s socially appropriate."

Nearly 90 percent of American teenagers say they are active users of social media, according to Pew Research Center statistics. For Sherman and her colleagues, that has been a boon to the scientific understanding of adolescent behavior. "Likes" are a quantifiable action of social endorsement that appears to strongly motivate adolescents who are highly sensitive to peer opinion.

"So now instead of learning about what’s cool from gestures or facial expressions," Sherman said, "there’s a number we can put to it."

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