Demi Moore smiles to make herself look young.

The 47-year-old actress - who is married to Ashton Kutcher, 32 - believes happiness is the key to looking youthful and claims she still feels as carefree as she did as a child.

She said: "I don't know if there is any particular secret to looking young, but there is one thing that I've thought of recently. I think that laughter and smiling are one of the best antidotes to ageing that you could possibly have. I think that, in general, I pretty much think of myself as still being, like, five. Maybe that's why my twitter picture is of me at five. That's how I feel. I'm just still trying to figure it all out myself."

The 'Joneses' star - who has daughters Rumer, 21, Scout, 18, and Tallulah, 16, with ex-husband Bruce Willis - also revealed she was driven to bare all for her role in 'Striptease' because she wanted to understand why she was so inhibited.

She explained to Parade.com: "I certainly have my inhibitions. Sometimes playing a role or posing for a picture is about getting rid of some of them. I remember I was driven by my inhibitions to want to do 'Striptease'. The major issue for me was not taking my clothes off, but dealing with why, in our puritanical society, we look down on women who do it for a living."