Dev Patel spent hours looking at himself in the mirror for his role in 'Lion'.

The 26-year-old actor plays adopted Saroo Brierley, who goes on a quest to find his birth parents in India, in the upcoming true-life tale and needed to go on a ''process of introspection'' to transform into his character, because he is usually much more ''super-hyperactive''.

He told Empire magazine: ''It required an energy shift. I'm a super-hyperactive kind of dude and the role required a level of stillness.

''Saroo had this emotional pain, this weight.

''I spent eight months prepping and it was all a process of introspection.

''I travelled around India on trains to get a feel of what it would be like, I wrote diaries, I visited orphanages.

''Garth would get me to stare in the mirror for an hour.

''It's amazing what you can see when you stop for a moment and really try to look inside yourself.''

Dev landed the role after a gruelling six-hour audition in which he worked through the entire script with director Garth Davis and ''lost his mind'' at the end.

He recalled: ''At the end of it, Garth said, 'Before you go, I'm wondering if you could just scream?' I was like, 'What do you mean?' He said, 'I want you to roar like a lion. Let go of emotion and completely purge the pain you'd feel in Saroo's situation. You don't have to do it.'

''And I was like, 'Of course I have to'. So I did and I completely lost my mind. I was jumping in at the deep end.''