May 6, 2010 -- Washing your hands does more than rinse away the guilt of sins or past misdeeds, it removes doubts about choices that have nothing to do with morality, such as choosing celery over carrots at the grocery store, a new study suggests.
Researchers at the University of Michigan say the act of hand washing helps people live with the decisions they make, alleviating cognitive dissonance, the uncomfortable feeling that comes from holding two opposing ideas in your mind at the same time.
The study is published in the May 7 issue of the journal Science.
“We know that washing your hands removes the need to feel that you made the right decision,” study author Spike W.S. Lee, a doctoral student in psychology at the University of Michigan, tells WebMD. “People always wonder if they make right decisions. What washing does is wash away the compulsion to justify the choice.”
The study, done with colleague Norbert Schwarz, PhD, expands on past research indicating that hand washing is associated psychologically by many people with guilt removal for perceived misdeeds, Lee tells WebMD.
Washing Away Doubt
The two scientists asked 40 undergraduate students to look through 30 CD covers as part of an alleged consumer survey. The participants picked 10 CDs they would like to own, ranking the music by preference.
Later they were offered a choice between their fifth- and sixth-ranked CDs as a token of appreciation. After they made a choice, the participants completed an ostensibly unrelated product survey, of liquid soap. Half looked at the bottle before answering, and the others actually tested the soap by washing their hands.
Still later the participants were asked to rank the 10 CDs again.
“People who merely examined the soap bottle dealt with their doubts about their decision by changing how they saw the CDs,” Schwarz says in a news release. “As in hundreds of earlier studies, once they had made a choice, they saw the chosen CD as much more attractive than before and the rejected CD as much less attractive.”
Hand-washing “eliminated this classic effect,” Schwarz says. “Once participants had washed their hands, they no longer needed to justify their choice when they ranked the CDs the second time around.”
Lee says in the news release that washing “reduces the influence of past behaviors and decisions that have no moral implications whatsoever.”
Hand Washing Mimics Washing Away Sin
The study results were replicated by getting participants to choose one of two fruit jams, and then cleanse their hands with antiseptic wipes in an ostensibly unrelated survey.
Again, participants “who merely examined an antiseptic wipe after choosing a jar of fruit jam expected the taste of the chosen jam to far exceed the taste of the rejected one,” Lee says in the news release. “This difference was eliminated when participants tested the antiseptic wipe by cleaning their hands.”
The results, he tells WebMD, show that as much as people feel that washing cleanses people of past immoral behaviors, it also can reduce the need to justify decisions.
Lee says this “clean slate” effect may have real-life implications. Washing hands may eliminate remorse for buying one car instead of another, of going to Rome instead of Paris on vacation, or even of choosing one partner over another.
Lee tells WebMD the phenomenon is a relic of the human notion of washing away sins.
“Lady Macbeth in Shakespeare tried to wash away her guilt of killing King Duncan,” he says. “Baptism is washing away past sins. We have to take these metaphors more seriously.”
Lee says the next avenue to explore is positive feelings. He notes that some baseball players may not wash “lucky” socks, and that people have a tendency not to wash their hands after touching someone famous.
“Maybe there is a tendency to want to wipe away past negative experiences and to avoid washing away positive ones,” Lee says.