Bradley Cooper says he is "the worst actor in the world" in real life.
The 37-year-old is known for his great performances in comedies such as The Hangover and Wedding Crashers.
However, Bradley finds it difficult to hide his emotions in real life.
"My friends say I may have a filter verbally, but you can always tell my emotional state by looking at my face," he confessed to ShortList magazine.
"Zach Galifianakis [The Hangover co-star] always says that, for an actor, I have the worst poker face in the world. In my real life, I'm the worst actor in the world."
Bradley temporarily took a step back from raucous comedies to star in drama Silver Linings Playbook.
Despite some black humour, the role is far more serious, with Bradley playing former teacher Pat Solitano who has just returned from a stint in a mental institution.
The star had to do a lot of research into his character's psychiatric disorder.
"Well, if you're diagnosed as having bipolar disorder, it's not like there's a sheet saying 'This is what it is'. David O Russell [director] says that mental illness is much like snowflakes - no two are the same," he explained.
"I watched a lot of footage to learn about people who have suffered mentally, but ultimately we just created a character based on his made-up history. Pat lives in a bit of a delusion in order to cope with his life. He doesn't have a filter."
Silver Linings Playbook also stars Jennifer Lawrence and hits cinemas worldwide from this month.
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