It turns out that Shakespeare was really onto something when he imagined Lady Macbeth trying to clean her conscience by rubbing invisible bloodstains from her hands. A few years ago, scientists asked people to describe a past unethical act. If people were then given a chance to clean their hands, they later expressed less guilt and shame than people who hadn't cleansed.
This finding fascinated Spike W. S. Lee, a psychology researcher at the University of Michigan, Ann Arbor. He wondered if hand washing could restore more than just a sense of moral purity. After all, "cleanliness is next to godliness," but people also often talk about "starting over with a clean slate."
"Maybe there is a broader phenomenon here," says Lee. "Anything from the past, any kind of negative emotional experiences, might be washed away."