The Ted actress told The Sun that she and her co-star Mark Wahlberg share "a very sick and nasty sense of humour".
"I'm not sure why I'm doing all these extreme dramas or comedies, though," she added.
"I'm much more conservative by nature than people think. I mean, I don't send out naked photos of myself or climb out of limousines without any panties."
Of being thought of as a sex symbol, Kunis added: "I appreciate the attention but I don't think of myself as particularly attractive at all.
"I also don't have that naturally sexual or sensuous way of behaving that some women have. I do have a pretty sharp sense of humour, though, and I think that has helped me."
She continued: "LA is filled with the most beautiful women in the world who all come here to be part of the entertainment industry.
"It's impossible to compete against that. Some women rely on their looks to make it and others know that they need to work hard to not just be treated as a pretty object and have a serious career."
Asked earlier this year how she protects herself from hacking and leaks, Kunis said: "Well, I don't send naked photos. Not that there's anything wrong with that."
The actress's sex scene with Natalie Portman in Darren Aronofsky's Black Swan was recently voted the best ever movie sex scene.
The best movie sex scenes - photo gallery:
Copyright: Rex Features Moviestore Collection/Rex Features