Brain scans are being used experimentally for everything from testing political leanings to determining whether a prisoner is a psychopath to lie detection. Now, for the third time in a year, a major study has been published questioning their reliability. The analysis, which has been accepted for publication in Annals of the New York Academy of Science, questions studies which have reported 80 or 90% correlations between specific regions of brain activity and personality traits and emotions.

After reviewing 63 journal articles which described studies using functional magnetic resonance imaging in which tests had been performed twice on the same people at different times, the authors conclude that, on average, there is only a 50% correlation between the brain regions that light up in the first and second tests in the same person.

"The thrust of our experiment is that it challenges the assumptions of how reliable the results from any one fMRI study may be," says Craig Bennett, a postdoctoral researcher in cognitive neuroscience at the University of California, Santa Barbara. "The end question we want to know is: if you did your experiment again, would the results — and the conclusions — be the same?" ~ Nature News, Mar 17