The Help star's factory worker mum, Mary Alice, was determined to build a better future for her six children, so she fought for U.S. welfare programmes, which provide support for low-income families.
But one ill-advised protest at the prestigious Brown University landed mother and baby daughter in jail.
David tells U.S. TV host Jay Leno, "My mother was an activist. I grew up in abject poverty. My mother fought for... welfare reform, and... my father always said, 'When I was in the barn, I was drinking beer, my friend was looking at me, and he said, Dan look at the TV, isn't that your wife and your daughter?'
"And it was my mother holding me, my finger was in my mouth, and we were being carted away by the police, being thrown in the back of a truck.
"We were in a holding cell for hours."
Her mother has always defended her decision to take her child to a protest.
Davis recalls, "She said, 'Well I wasn't gonna leave y'all at home, y'all were gonna be right there marching with me.'"