Why Lying Makes You Want to Wash Your Hands

Participants were asked to recall something wrong they had done, then offered a choice of gift: tissues or a pencil. In the group recalling a bad deed, tissues were chosen noticeably more often. That led to the idea that people wanted to cleanse themselves.

There was a second part, too. People who washed their hands after recalling the event were later less likely to want to make amends by helping. It seemed that physical cleansing somehow settled the moral issue.

The result quickly spread through textbooks and popular books. It seemed to explain ritual washing in religions and the famous hand-washing scene in Shakespeare, so it looked very convincing.

When the experiment was repeated with samples several times larger than the original and in different countries, the effect did not replicate. The difference between the groups fell within the range of chance, and this happened in several independent checks.

Cases like this helped establish the practice of preregistering experiments: researchers announce in advance what they will measure and how, and can no longer choose a successful analysis after the fact.

It's worth clarifying what was not confirmed: the link between a specific feeling of guilt and the urge to wash your hands. The link between disgust and moral judgments is a separate topic, and the results there look more consistent, although they are also debated.

Ritual washing has not disappeared, of course, and exists in many cultures. But it is explained not by an automatic mental reaction, but by a cultural logic of cleansing that people learn along with customs.