Whatever else it achieves in offering observations about friendship and love in the modern age, “Life Partners” is definitive on one subject: the tyranny of the smartphone.

The devices intrude on almost every scene — not as a way of making a point about our wired existence, but just as a part of everyday life (one subplot involves texting while driving, and the minor fender-bender that results).

The characters are accustomed to every conversation, flirtation, or seduction being punctuated by the buzzing WHAAH of a phone vibrating its latest demand. No wonder the characters can’t concentrate long enough to straighten out their lives.

At the heart of the film is the longtime friendship between Sasha (Leighton Meester) and Paige (Gillian Jacobs), 29-year-olds who like to drink wine, stage mock public arguments, and provide live running commentary for reality-TV shows.

Sasha is lesbian and Paige is straight, but this doesn’t have too much to do with the story’s main turn: Paige meets a boyish Mr. Right (Adam Brody), and the old friends must delicately renegotiate their time together.

Director Susanna Fogel works hard to make them specific people, not types: Paige is control-oriented and condescending, Sasha keeps dating young airheads. There’s also a nice wrinkle in what seems to be a cliché about Sasha, who works at a meaningless job but has a true calling as a singer-songwriter. But what if (in opposition to most chase-your-dream movie scenarios) the true calling isn’t actually all that compelling anymore?

These are valid storytelling beats, and “Life Partners” has energetic turns from its engaging leads, all of whom came from television (Meester became a star on “Gossip Girl,” Jacobs was a regular on “Community”). As veterans of same-sex dating battles, Gabourey Sidibe and Beth Dover provide some laughs.

But for all the nice effort, I didn’t really believe “Life Partners.” From scene to scene, everybody tries too hard to convince us of how informal and funny it all is. Meester and Jacobs unleash the brassy zingers like nobody’s business, but they don’t convey the laid-back, lived-in casualness of old friends who know what the other person is going to say before she says it.

Of course, when the world is keyed to the rhythm of the smartphone, no wonder everybody seems jumpy.

“Life Partners” (two stars)

Two best friends — one lesbian (Leighton Meester), one straight (Gillian Jacobs) — confront the shift when one of them gets in a serious relationship. Some good effort here, although the movie tries so hard to tell us how funny and casual this all is that it doesn’t quite convince.

Rating: R, for language, subject matter

Showing: Seven Gables