Think you saw something that you really didn't? Your mind may be playing tricks on you.

In a study in the journal Nature Neuroscience, co-authors Ken A. Paller, Ph.D., a psychology professor at Northwestern University (NU), and Brian Gonsalves, a Ph.D. candidate also at NU, asked a group of people to visualize common objects as they were being cued with the corresponding word. In some instances, the words were accompanied by actual images.

After the sequences, the researchers surprised the group with a memory test that asked them to decide whether or not they had been shown pictures for the words. Test results revealed that, in 30 percent of the trials, participants believed they had seen pictures of words that had not been accompanied by a physical visual image, which Gonsalves also found evidence of in the participants' brain wave activity.

"There was more positive electricity over the visual cortex area for accurate picture memories than for false ones," he explains. Gonsalves and Paller are working on a similar study to localize brain activity in the visual regions of the cerebral cortex, research which may help further explain why the brain creates false memories.