Excerpt from this article:
…New research shows that likes appear to be somewhat intoxicating to teenagers. The same reward center in the brain that is involved in the sensation of pleasure and activated by thoughts of sex, money or ice cream also is turned on when teenagers see their photos getting a lot of likes on social media.
…Teenagers were more likely to give a like to an image that had already gotten dozens of likes, even if it was a fairly banal picture of a plate of food or a pair of sunglasses. They were less apt to like the same kind of image if it had gotten few likes.
…“Conformity is part of adolescence, and some of it is normal,” said Ms. Sherman, who prefers the term “peer influence” to “peer pressure.” “It’s how teenagers learn the rules of how to communicate and how to develop relationships.”
…The likes are “potentially serving as a social cue, orienting them to what is cool or socially appropriate,” Ms. Sherman said. “Learning about the social world is a really important task of adolescence.”