Clean Hands, Clear Conscience

It's human nature to regret our decisions. Make a choice and you're likely to think you made the wrong one. But not if you wash your hands, say scientists from the University of Michigan in a new study from Science.

In the experiment, 40 participants were asked to select and rank 10 music CDs. They were then offered the choice of either their fifth- or sixth-ranked CDs as a "token of appreciation."  After the participant made their choice, they were asked to participate in a survey about liquid soaps--half were allowed only to examine the soap bottle while the other half washed their hands with the product. Finally, they were asked to rank again the 10 CDs. (The experiment was later repeated with jams instead of CDs and hand wipes instead of soaps.)

Individuals who washed their hands tended to stick with their original rankings while those who only examined the soap lowered the rank of their CD of choice by about two places on average. In the jam experiment, hand washers also tended to be more likely to stick with their original choice.

The scientists write:

These findings indicate that the psychological impact of physical cleansing extends beyond the moral domain. Much as washing can cleanse us from traces of past immoral behavior, it can also cleanse us from traces of past decisions, reducing the need to justify them.

That said, it didn't seem to help Lady Macbeth too much.

Sarah Zielinski | | READ MORE

Sarah Zielinski is an award-winning science writer and editor. She is a contributing writer in science for Smithsonian.com and blogs at Wild Things, which appears on Science News.