NPR's Morning Edition today explored the psychology of hand-washing, specifically, the so-called "Macbeth" effect, in which the literal cleansing of hands can also offer a psychic scrubbing away of mental turmoil.
Reporter Nell Greenfieldboyce reviews earlier research on this phenomenon:
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."
In new studies, researchers revisited the question of whether hand-washing somehow cleanses the psychological stress of decision-making. The results suggest that maybe it does, but the larger impacts remain unclear:
(Researcher) Schwarz says it's too soon to know whether people should head for a sink after making a tough choice.
He says washing may help decision-makers, by scrubbing away mental turmoil. But perhaps if they don't go through the usual post-decision process of justifying their choice, they might feel more remorse in the long run.
"We may not do you a favor when you wash your hands and you're not doing that cognitive work to make your decisions appear in the best possible light," Schwarz explains, adding that this is something they want to investigate in future studies.
This program aired on May 6, 2010. The audio for this program is not available.