Karen Gillan says shaving her head for 'Guardians of the Galaxy' was a ''fun social experiment''.

The former 'Doctor Who' actress stars as Nebula - a blue-skinned deadly assassin - in the sci-fi adventure film and she's confessed that although she had to shave her head for the role, she's glad she did because she found the experience ''liberating''.

Quizzed on how she'd found having a bald head, she told British TV's 'Lorraine': ''That was a really weird experience, but also it was weirdly liberating and fun and interesting as a social experiment, just to see how differently people would treat me.

''I think people were pretty intimidated by me. I really ... I kind of liked it while I was playing the role.''

The 26-year-old star - who appears alongside Chris Pratt, Zoe Saldana and Dave Bautista in the Marvel Comics film directed by James Gunn - also admitted that she enjoyed playing the enemy for the first time.

She explained: ''It was really fun. I've never played a sort of bad character who's gone to the dark side so that was really fun to be able to explore.''

Karen also revealed that although she enjoyed the experience of shaving off all her hair, she found herself missing having something to hide behind.

She added: ''I realised that I did that [used it as a shield] after it was gone and I was like, 'Ahh there's no hiding curtains'.''