Henry Joost and Ariel Schulman, the directing team behind “Catfish,” “Paranormal Activity 3” and “4,” and the new teen-oriented cyber-thriller “Nerve,” know how to affect coolness and currency without seeming to try too hard — a rarity in Hollywood. Their films show young people using computers and social media the way actual youths do (more or less; Emma Roberts’ Macbook does turn into a touchscreen a couple of times here), with slang that’s topical but not forced.

But all the street cred in the world can’t un-dumb “Nerve,” a ludicrous, self-serious semi-thriller about the dangers of peer pressure, online anonymity, and cyberbullying. It’s what you’d get if a socially conscious Millennial made an Afterschool Special, and though it’s fitfully engaging and periodically watchable, it can’t overcome its inherent weakness: it’s about idiots doing stupid things for no good reason. Show a woman risking her life to save her children, I’m interested. Show her risking her life for a couple hundred dollars, I’m out.

It stars Emma Roberts as Vee, a mildly timid Staten Island high-schooler whose brazen best friend, Sydney (Emily Meade), cajoles her into participating in a smartphone game of public dares called Nerve. The people watching your livestream suggest dares, and there are cash prizes for accomplishing them. The riskier the stunt, and the more watchers you have, the more the payout. Apart from the massive liability issues, it’s actually a great idea for a game.

Vee’s first dare (to kiss a stranger) introduces her to Ian (Dave Franco), who turns out to be a fellow Nerve participant. As the online audience finds Vee and Ian to be a cute couple, their dares are interconnected for the rest of the night. But maybe there is more to Ian and the game than Vee realizes?? Vee’s platonic-but-thirsty guy friend Tommy (Miles Heizer), who happens to be an expert computer hacker (this will come in handy later), watches nervously from the sidelines, and Sydney gets jealous over the size of Vee’s audience. Vee’s mother (Juliette Lewis), oblivious to everything, appears now and then because the movie (adapted by Jessica Sharzer from Jeanne Ryan’s novel) figured at least one of these kids needed to have a parent.

The watchers are right about Roberts and Franco being a cute couple, and “Nerve” gets by for a while on the characters’ naive enthusiasm. But as the dares get increasingly dangerous (blindfolded motorcycling, etc.), and as everyone’s motives become clearer, the story collapses into absurdity, then adds some heavy-handed moralizing for good measure. And what lessons do we learn? Oh, just obvious ones like DON’T DO LIFE-OR-DEATH STUNTS JUST BECAUSE ANONYMOUS STRANGERS TOLD YOU TO, YOU MORON.

C+ (1 hr., 36 min.; PG-13, some profanity, brief partial nudity, a little violence and peril.)