Did you know that Adolf Hitler had three testicles?
You didn't? Well, you are right. That is just an urban legend -- one that I have just created.
In fact, if anyone tells you that Hitler had three testicles, they are either misinformed or they are lying.
Why am I mentioning Hitler's three testicles to you right now? Because by mentioning the myth of his three testicles, and debunking that same myth, I am actually increasing the odds that some time in the future you will mistakenly believe that Hitler really did have excess, um, baggage.
Behavioral scientists have discovered that familiarity breeds belief. In research studies, they have exposed people to series of true and false messages, telling people at the same time which of those messages were true or false. Later, they exposed people to these same messages, and asked them whether they thought the messages were true or false. They found that previous exposure to these messages increased the number of people who believed these messages were true, even the messages that had been identified as false.
How does this happen? People remember hearing the message ("Hmmm, three testicles, that sounds familiar"), but forget learning that the message was false.