“The type of reinforcement schedule that is the most reinforcing is what’s called an intermittent schedule,” she explains. “So, you have a rat pushing a lever and he gets rewarded, but not in a predictable way. Many times, that animal pushes that lever and nothing comes, but every once in a while, it gets a great treat. So the rat keeps pressing and pressing and pressing even though there’s not much reinforcement coming because every once in a while, it’s just great.”

She admits it’s hardcore behaviorism to make this comparison, but says it’s explains a lot about our addiction to digital communication, and this doesn’t just apply to teens. Underwood suggests email as an adult equivalent, explaining that even though most email is utilitarian and boring (emails for work or junk mail, for example), every so often a “marvelously reinforcing” message (like exciting professional news or a letter from an old friend) will come through the pipeline. Those tiny nuggets of greatness peppered in lead many adults to check their email dozens of times a day. Where teens take things a step further is in their output.

“These adolescents are at an age where they’re so desperate for connectedness with their peer group,” Underwood explains. “They have this way that they can just lob out information, lob out communication to their whole group of peers and then get something back.”

If getting positive reinforcement from one’s peer group is addictive, getting an elusive follow or retweet from a celebrity is the ultimate high—not to mention a claim to fame in its own right.

“If they do get a tweet back [from a celebrity], they forward it to their whole community. So that’s a huge status thing,” Underwood says.

When it comes to online fan communities, more than just an addiction to positive reinforcement is at play. Young people especially rely on a sense of community during their formative years. While primary communities are still developing at school, the Internet provides the means for adolescents to engage in subcommunities of like-minded peers around the world who share those interests.

Developmental psychologist Dr. Kaveri Subrahmanyam says these communities can be an important part of adolescent development.

“I teach an adolescent psychology class and we talk about cliques and crowds and historically, crowds have been useful for identity development,” she explains. “I think to some extent some of these online communities are like online versions of crowds and I think they’re helping with their identity. There is data suggesting that self-presentation online is linked to identity. We don’t know yet if it’s positive or negative, but it’s certainly all self-presentation. It must be playing some sort of role in how they solidify their identities.”

Teens’ and tweens’ affiliation with these communities is solidified by a new trend in celebrity worship: The Fan Base Name. Justin Bieber has his Beliebers (the dedicated group most would credit with starting the trend). One Direction have their Directioners. Katy Perry’s fans are KatyCats. Lady Gaga’s are her Little Monsters. Some celebrities help coin these terms, but when they don’t, fans take it upon themselves to name the community. Even pushback from the celebrity they love does little to stop the momentum of a popular fan name. Lorde, for example, has spoken out about her desire to not have a name for her fanbase.