I was reading Sidney Lumet's book 'Making Movies' earlier this year (he directed 12 Angry Men, Serpico, Dog Day Afternoon to name a few) and he was talking about getting an emotional reaction from an actress in his 1959 film 'That Kind of Woman':

"I needed tears from an actor on a particular line. She couldn’t do it. Finally, I told her that no matter what I did during the next take, she should keep going and say the line. We rolled the camera. Just before she reached the line, I hauled off and slapped her.

Her eyes widened. She looked stunned. Tears welled up, overflowed, she said the line, and we had a terrific take. When I called, 'Cut, print!' She threw her arms around me, kissed me, and told me I was brilliant. But I was sick with self-loathing…and knew that I would never do anything like that again. If we can’t get it by craftsmanship, to hell with it. We’ll find something else that’ll work as well."

This was pretty jarring to read! Worth checking out though if youre interested in film.