Scarlett Johansson finds monogamy "hard work".

The 'Lost In Translation' actress doesn't think it is natural to have just one sexual partner, but insists her views don't mean she is "promiscuous".

Scarlett said in an interview with Glamour magazine: "Contrary to popular belief, I'm not promiscuous. There seems to be a mistaken belief that I'm sexually available somehow - which is not to say I'm not open minded about sex. Yet I wouldn't say I'm a serial monogamist either.

"I went through periods of time when I was single. But when I'm in a relationship, I'm in a relationship. I can get flack for saying this, but I do believe that human beings aren't instinctively monogamous.

"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."

The blonde star broke up with her boyfriend of two years Josh Hartnett late last year.

The 22-year-old actress recently confessed she gets tested for HIV and other sexually transmitted diseases every six months, stating that sexually active people have to be "socially aware".