Johansson says ‘I’m not promiscuous’

NEW YORK — Scarlett Johansson says that while monogamy might go against instinct, she’s happy in her relationship with boyfriend and recent “Black Dahlia” co-star Josh Hartnett.

“Josh is very sweet,” the 21-year-old actress says in an interview in Allure magazine’s November issue, on newsstands Oct. 24. “He’s a good boy. A great person. I’m very lucky and I’m very happy. Contrary to popular belief, I’m not promiscuous.

“There does seem to be a mistaken belief out there that I am sexually available somehow — which is not to say that I’m not open-minded about sex,” she continues. “Yet I wouldn’t say I’m a serial monogamist, either. I mean, I went through periods of time when I was, ah, single. But when I’m in a relationship, I’m in a relationship.”

But Johansson, whose films include “Lost in Translation” and “Match Point,” still acknowledges monogamy might not be natural.

Slideshow: Scarlett Johansson “I do think on some basic level we are animals, and by instinct we kind of breed accordingly,” she says. “But as much as I believe that, I work really hard when I’m in a relationship to make it work in a monogamous way.”

Johansson also encourages testing for sexually transmitted diseases.

“I get tested for HIV twice a year. ... One has to be socially aware,” she says. “It’s part of being a decent human, to be tested for STDs. It’s just disgusting behavior when people don’t. It’s so irresponsible.”