Ashton Kutcher plays Adam and Natalie Portman plays Emma in “No Strings Attached.” (photos courtesy of Paramount Pictures)

No Strings Attached” is no “Black Swan”, but Natalie Portman could run around on screen yelling, “crazy hamster,” for two hours and she’d probably find a way to make it interesting. Somewhere between “10 Things I Hate About You” and “The Ugly Truth”, Ashton Kutcher and Portman provide solid performances in this January rom-com.

The story begins when our leading stars meet at camp as children. Eventually, they’ll have several anti-climactic run-ins until a drunken stupor finally brings them together. Adam (Kutcher) is the son of a celebrity trying to make a name for himself without the help of his father, and Emma (Portman) is a doctor in training, so she doesn’t have the free time for love. So rather than take the big plunge — or even try to dip her feet — Emma proposes that the two continue seeing each other on a solely sexual basis. Friends with benefits. Sex buddies. No strings attached. Of course Adam tries to play it off like he’s just discovered the heterosexual Holy Grail — sex without spooning or dinner first — he eventually wants more. Cue the dramatic (and all too sexual) tension.

We’ve heard this story before, however it’s normally the dude who just wants sex. Emma is on the career path and the thought of hand holding and meeting the parents is ironically more frightening than becoming intimate with someone she doesn’t know that well.

Adam (Ashton Kutcher) tries to sweep Emma (Natalie Portman) off her feet with an elegant bouqet of carrots in “No Strings Attached.” (Photo courtesy of Paramount Pictures)

As humor goes, there are plenty of R-rated rom-coms that do it better than this one (just try some stuff with Katherine Heigl or…OK, so there’s not that many non-PG-13 installments), but a story where spooning feels too real is quite welcome in place of disasters such as “The Tourist”, where the construction of love is as non-complicated as Miley Cyrus’ lyrics.

More than humor, there’s an unexpected sincerity throughout the film. Sex with love is tragic and sex with a new partner, as portrayed in their first encounter, isn’t a romantic encounter but a bumpy ride. Their relationship is riddled with uncomfortable dialogue and sad, yet all too real moments, where the “get over yourself” principle is largely ignored.

I’ll say it again: Portman is a screen gem who can do little wrong. It’s refreshing to see her in a lighthearted, yet still sincere, role where she doesn’t have to battle internal demons, deal with a soldier love triangle or hang out with a mask-toting terrorist. She can simply play the romance game — and she’s adorable at it. She even pumps out a few memorable one-liners.

Even Kutcher moves past his Kelso from “That ‘70s Show” persona, and tries a more reserved role. He’s not a lady’s man but a soft-spoken guy with a romantic heart and some bad luck with former girlfriends who end up dating his dad, Alvin (Kevin Kline).

Director Ivan Reitman may have won me over with both “Ghostbusters” films, but his latest attempt at entertaining, “My Super Ex-Girlfriend”, was the epitome of forgettable. Don’t get me wrong, “No Strings Attached” is a cute film, but it’s in line with the director’s track record this century (let’s see how he’ll do with the third installment for “Ghostbusters” set for next year). Still, performances, while predictable, are engaging, even if some of the jokes fall flat.

There are several strong supporting characters here, but they’re far too underused —only getting appropriate screen time in a prologue during the credits. Kevin Kline tries his hand as the superficial father who doesn’t know how to grow up and ease up on the fake-and-bake.

Lake Bell tones down the supermodel persona from “It’s Complicated”, trying out the role of a nerdy and far too talkative TV show manager named Lucy. Chris “Ludacris” Bridges, as Wallace, and Jake M. Johnson, as Eli, are the decent friends and sexual consciousnesses of Adam. Finally, Emma’s sister, Katie (Olivia Thirlby), and roommates, Patrice (Greta Gerwig) and Shira (Mindy Kaling of “The Office”) have some brief moments as well. Oh yeah, Carey Elwes (farmboy from “The Princess Bride”) also has an odd bit part that never goes anywhere.

As far as date movies go, “No Strings Attached” is a nice way to remind a significant other that sex, or even just a kiss, is never a neutral matter. It’s got all the sappiness to make a first date go over well and enough emotion to remind other couples to take things a little more seriously.