It's easy to make a false memory. All you need is a friend and this list of words.
Read the words to your friend slowly (about 1 to 2 seconds per word). Then ask your friend to remember as many of the words as he or she can. Here's the list: bed, rest, awake, tired, dream, wake, snooze, blanket, doze, slumber, snore, nap, peace, yawn, drowsy.
Most people can remember about half the words. But the amazing thing is, about 55% of people who take this test swear they remember the word sleep -- a word that isn't even on the list.
The reason some people remember the word sleep is that words like bed, snooze and doze remind them of sleep. "Thoughts that are sparked during an event can later be remembered as having occurred during that event," said Kathleen McDermott of Washington University in St. Louis.
This is important to understanding eyewitness testimony because it suggests a way that witnesses might be fooled, said McDermott, who developed this test with colleague Henry Roediger III.
For example, witnesses might see a crime and think that the perpetrator resembles somebody they have seen in the neighborhood once or twice.
Later, these witnesses might testify that the person they were reminded of actually committed the crime.
That may sound farfetched, but it has happened in dozens of cases that were later overturned by DNA evidence.