Watching a film that excites sexual love or romance can boost progesterone levels more than 10 percent in men and women, making them feel more romantic.
Researchers at the University of Michigan also found that watching darker films, like the "Godfather" had the opposite effect of dampening those feelings.
The research team tested three different groups. One viewed a romantic scene from "The Bridges of Madison County", a second group watched portions of "The Godfather Part II", while a third group watched a documentary on the Amazon rainforest. Each group had hormonal levels tested immediately before, after and 45 minutes after viewing the 30 minutes of tape.
Clint Eastwood did nothing for women's testosterone levels in "The Bridges of Madison County". Men on the other hand had a decrease in their testosterone levels.
Don and Vito aroused a different sort of passion in the "Godfather", men with the highest levels of testosterone had them soar by as much as 30 per cent more.
Finally men and women watching an Amazon rain forest documentary were unaffected, in fact researchers had great difficulty waking this sample group up.
"When you're watching movies, your hormones are responding, not just your mind," said Oliver Schultheiss, a psychology professor who led the study.
"If you want to learn about someone's personality, look at their video collection."
Professor Schultheiss published his study in the journal Hormones and Behaviour.