George Clooney refuses to be unpleasant when directing films.

The 62-year-old star has helmed the sports drama 'The Boys in the Boat' and has learned from bad experiences on past film sets in terms of treatment of the cast and crew.

George told Total Film magazine: "Well, I've been on sets with miserable directors. I've been on sets with directors who yell and scream. To me, it doesn't matter what the product is at that point.

"This is a job where there's 300 people on the set trying to do the best they can. There is no reason and no purpose for people being treated badly. I hate it, and I won't do it.

"I've had directors who I like personally, but I know them reputationally, and within the last few months they've come to me and said, 'When are we going to work together?'

"And I go, 'We're never going to work together, dude. I think you're great, but I'll never work with you because you're mean, and I can't be around it.'"

The movie follows the University of Washington rowing team and their attempts to compete at the 1936 Olympic Games in Berlin but Clooney explained that it was the "simplistic" story rather than the time period that held the most appeal to him.

The 'Burn After Reading' actor said: "Well, I don't actually run towards period pieces, but I found some very simplistic, interesting stories. I like to do films that are challenging. And then, this one, the challenge was about making the film, not about the story.

"This is one where we know where you're going to stand on it. You're against Hitler unless, you know, you're some knucklehead! And we were rooting for this team to win. We're rooting for these guys. That's a fun, simplistic story."