Shakespeare’s Lady Macbeth may have had the right idea when she scrubbed her hands following the murder of King Duncan. An odd new study suggests that hand washing may help people deal with the emotional consequences of decisions–and not just big decisions, like whether or not to participate in regicide, but also minor calls, like which free CD to take home.

[Psychology researcher Spike W. S. Lee] and a colleague named Norbert Schwarz decided to test hand washing’s effect on one kind of bad feeling: the lingering tension we feel after being forced to choose between two attractive options, because picking one option makes us feel that we’ve lost the other. Psychologists know that people usually try to soothe this inner conflict by later exaggerating the positive aspects of their choice. “In other words, after they make the choice, they will like the chosen option more than before the choice,” Lee explains [NPR].

For the study, published in Science, the researchers told students they were evaluating products for a consumer survey. The students first ranked 10 CDs in order of preference, and were then told they could take home either their fifth- or sixth-ranked CD as a token of appreciation. After they made their choices, they were told it was time to evaluate a liquid soap–but some students washed with the soap, while others only looked at its packaging. Finally, the students were asked to rank the same set of CDs again.

When the two groups re-ranked their ten CDs, students that did not wash their hands ranked the CD they chose higher, as if to indicate to themselves that they wanted that CD anyway. Students that did wash their hands, though, ranked their chosen CD about the same, showing that hand-washing somehow dispensed with the need to justify a choice [Ars Technica].

The results suggest that hand washing “wiped the slate clean,” Lee says, and removed the emotional baggage and rationalizations associated with the students’ choices. In another version of the experiment, researchers got the same results when students cleaned their hands with an antiseptic wipe after choosing a jam, which implies that a traditional scrub down with soap and water isn’t required.

While this is a neat trick, Lee notes that the typical mental processes that surround decision making have served humans well.

“Justification has a purpose, it makes people feel good. Washing away the need to justify past decisions also washes away the cognitive good.” It’s possible that those who washed their hands won’t enjoy the CD or jam as much as their unwashed counterparts will, he says [New Scientist].

Related Content:
Discoblog: Does Washing Your Hands Make You Less Judgmental?
80beats: Warm Hands Give People a Friendly, Generous Outlook
DISCOVER: The Biology of …Hand-Washing

Image: flickr / Arlington County