"There's no room for honesty in a healthy relationship," says Coles Burroughs (Mark Ruffalo) about a woman he has betrayed by having sex with her best friend. "You guys still want to go to the beach this weekend?"

The question is a fairly good indicator of Coles's character, or the lack of it. He is casual about everything, especially things that matter. The betrayed woman's name is Sam (Maya Stange) and he will be unable to forget her entirely, though he will easily and conveniently forget what a jerk he has been.

Coles is the uneasy centre of xx/xy. He is an aspiring filmmaker with a Frank Zappa moustache and a runaway libido. As the movie opens, we see him jumping the turnstiles into the New York City subway. He has the swagger and style of a rebel icon.

It is 1993 and he is on his way to Sarah Lawrence College where he will crash a party and do plenty of drugs and alcohol. He will attempt a three-way with two young women, but the ménage will collapse into a farce. He will translate that experience into hand-sketched images of three bodies that glide and morph into each other. Coles, you see, is an artist.

Ten years later, he is living in New York City with the immaculate Claire (Petra Wright). Incredibly, they have been together for five years, which, for someone like Coles, is a long time indeed. He is no longer a grubby artist. Instead, he has a sleek new haircut, a swanky Manhattan loft, and a job as an animator for an unashamedly kitschy advertising agency.

His most recent masterpiece features bikini-clad tacos.

Then, of course, Coles bumps into Sam, who has just returned from London, where she turned down a marriage proposal. They go back to Coles's place and end up on the couch. And where is Claire, you ask? Oh, she's out getting Coles a hard-to-find birthday gift, the Claire Denis DVD box set.

Shot on gritty digital video, the opening sequence and the scenes of profligate partying that follow have the sort of drugged glamour you would expect from a movie about growing up privileged and stoned in NYC.

There are long sequences that seem to have been inspired by music videos: endless slow-motion sequences of beautiful people disporting themselves in Central Park, as loud world music detonates on the soundtrack and fireworks light up the night.

Unfortunately, at the end of play, all you are left with is a morality tale that is hardly original in its tired take on modern relationships. The love triangle is well-mined territory, after all, and not easy to see afresh.

The question first-time director Austin Chick posits is this: how does a sleazeball dude who finds it very difficult to keep his business in his pants find redemption? The answer is, he does not.

In fact, when the movie winds down to its long-drawn and essentially trivial denouement during a weekend at the beach, Coles is revealed as the weak-kneed fool he has always been.

Sam and Thea (the other woman) come out a little better. Claire comes out best.

And the moral? Sexual jealousy will occur even in the most modern arenas. If you do not need to go to the movies for that kind of empty moralising, give xx/xy a miss and rent Jules et Jim.