You can wash away your troubles, with soap

Religious rites like baptism make psychological sense, the article suggests. Says Lee: "Cleansing is about the removal of residues." By washing the hands, taking a shower, or even thinking of doing so, "people can rid themselves of a sense of immorality, lucky or unlucky feelings, or doubt about a decision. The bodily experience of removing physical residues can provide the basis of removing more abstract mental residues."

One study the authors discuss found that people asked to judge the moral wrongdoing of others saw them as worse when exposed to an unkempt room or bad odor than when sitting in a clean room. In another study, participants asked to think of a moral wrongdoing of their own felt less guilty after using an antiseptic hand wipe; they were also less likely to volunteer for a good deed to assuage that guilt. Even imagining yourself either "clean and fresh" or "dirty and stinky" affects your judgments of others' acts, such as masturbation or abortion. The "clean" participants in one study not only judged others more harshly, they judged themselves as more moral than others.

Cleansing works for other mental discomforts, too, such as post-decision doubt. To resolve this doubt, people who opted for one of two similar jams felt better about their choice after making the decision, a well-known tendency called choice justification. But if people were given a hand wipe to use, they no longer justified their choice: They had wiped off their doubt. Using soap showed similar results after a bad luck streak in gambling: After washing, participants started to bet higher stakes, suggesting they had "washed away" their bad luck.

But we can't conclude that people who bathe a lot are happier. "Cleansing removes the residual influence of earlier experience," says Lee. If that experience was positive, it would go down the drain too. In fact, washing one's hands after reminiscing about a positive event limits the warm glow of happy memories, leaving people less satisfied.

So was Shakespeare, so monumentally astute about human emotion, wrong to portray Lady Macbeth as unable to wash the metaphoric blood from her hands? The authors' research suggests she might have had the wrong body part in the soapy water. In one experiment, participants were induced to tell a malicious lie either by email or voice mail. Afterwards, those who had lied "by mouth" evaluated a mouthwash more highly than a hand sanitizer, while those who transgressed "by hand" showed the opposite preference. "Lady Macbeth is an interesting example. Her unethical behavior is with her mouth" -- she pushed her husband to commit murder -- "but she's trying to get the imaginary blood stains off her hands," says Lee. "I won't push it too far, but it fits nicely with research."