>Functional MRI measures blood flow as a proxy for brain activity. It shows where blood is being sent in the brain, presumably because neurons in that area are

>Functional MRI measures blood flow as a proxy for brain activity. It shows where blood is being sent in the brain, presumably because neurons in that area are more active during a mental task. >The problem is that the level of activity for any given person probably won't be the same twice, and a measure that changes every time it is collected cannot be applied to predict anyone's future mental health or behavior. >Hariri and his colleagues reexamined 56 published papers based on fMRI data to gauge their reliability across 90 experiments. Hariri said the researchers recognized that "the correlation between one scan and a second is not even fair, it's poor."