One of the questions I commonly receive about MRI research on pedophilia is: How do we know what causes what? Comparing the brain scans of pedophiles with non-pedophiles gives us a correlation, and correlation does not necessarily mean causation.
It is true that correlation does not equal causation, but that does not mean we are powerless about it either. To understand how to attack this kind of problem, we need to recall a few important (but pretty rarely discussed) principles of science:
