We all know that people will tell you one thing and do another. Social desirability is the term behavioral scientists use to describe how people will deliberately give false responses so as to present themselves in the best light. They’ll tell us they do things they don’t, and tell us they don’t do things they do. This is especially so on sensitive topics, but even exists in simple day-to-day activities.

Ask the people you know and almost all of them will tell you they wash their hands every time after using the toilet. People say they wash their hands because they know they’re supposed to, and know they’ll look bad if they say they don’t. But systematic observation and recording tells a different story.

Multiple studies show 95% of people report they always wash their hands after using a public restroom. Observed rates are quite contradictory.

• Gender differences? About 80% of women wash their hands, compared to about 50% of men.
• What about people who handle food in restaurants and who are required by law to wash their hands? You would hope they have higher rates, but alas, only one in three actually wash their hands every time they use the bathroom.
• How about healthcare workers in hospitals, highly aware of the dangers of transmitting germs and infections? Nurses 75%, doctors 50%.

The Centers for Disease Control say proper hand washing includes soap and water, but a third of those who “wash” their hands are only rinsing them and not using any soap at all.

The CDC also say proper hand washing takes 15-20 seconds, while the average observed hand washing time is only six seconds. The CDC’s conclusion is that only one person in twenty washes their hands properly enough to kill germs that cause infections.

The best researchers know that if you want to know what someone really does, observe them instead of asking.

For a look at Elvis Presley’s hand washing practices, check out this YouTube video, and wait for the chorus.