Amanda Seyfried says her parents' marriage makes her believe in true love.

The 27-year-old actress' mother Ann and father Jack have been married for over 30 years and their commitment to one another has convinced her that her 'Mr. Right' is out there somewhere as well as giving her an admiration for people who don't cheat.

Speaking to The Sun newspaper, Amanda - who is dating actor Justin Long and was previously in a three-year relationship with her 'Mamma Mia' co-star Dominic Cooper - said: ''I have learned from my mom, Ann, the importance of a long relationship. She and my dad Jack have been together for more than 30 years. It always gives me hope of a good long-term relationship. I have had boyfriends and I have been in love. I would never think of sleeping with someone else when I am in a relationship. The result is that I admire people who are able to avoid affairs.''

Amanda admits her mother - an occupational therapist - has been a huge influence on her life and helped her cope with her difficult teen years, during which she was self-conscious about her looks and figure.

She revealed: ''My mom has an ability to stay calm. She is an occupational therapist and always appears to be in control of a situation. My mom knew that I suffered from body issues in my teens. I was way too shy. I felt ugly. I was skinny and had braces on my teeth. Yet I started acting as a kid in the local civic theatre just for the fun of it. Then I was asked to become a model in my teens. I don't know why. It's a slow process for most of us in our teens.''

Although Ann has always supported her famous daughter in all her choice, Amanda is sure her mother isn't a fan of her stripping off for her film roles, most recently as porn star Linda Lovelace in the biopic 'Lovelace'.

Amanda - who kissed Megan Fox in horror movie 'Jennifer's Body' - said: ''Does my mom always approve of everything I do? She probably does not like me taking my clothes off for films. But because she manages to keep calm and never blurts out her feelings, that gives me encouragement to go for the roles I think are best.''