Brain scans of 39 men with psychopathic traits uncovered a striking structural pattern, with one trait dimension standing out from the rest. Their brain scans raised a different question: whether those behavioral differences were accompanied by measurable differences in brain structure. Researchers examined MRI data from 39 German men with Psychopathy Check-List-Revised scores of 20 or higher, comparing regional brain volumes with those of age-matched controls. After accounting for study site, age and intracranial volume, total brain volume was 1.45% lower in the psychopathy group. But detailed regional group differences such as this did not remain significant after correction for multiple testing, unlike the broader reduction in brain volume.