Functional magnetic resonance image scans have been used as lie detectors which have been used in murder trials as well as testing whether conservatives are psychopaths or liberals are more broad-minded. Yet recent studies suggest that the scans are only giving insight into a very small part of the brain. Most research with fMRI scans have very small sample sizes. The very useful blog Neuroskeptic reviews two recent articles which had very large sample sizes.
Read More: Are brain scans telling the truth?