If you’re interested in the methodology used, here’s a link to the full study.

Essentially, they didn’t ask if the person thought they were a psychopath; They asked questions to which the answers reveal underlying character traits. Of course, no method of data collection is perfect. If you want to know what steps were taken to filter out insincere subjects, that information can also be found within the full study.

Wow, folded like a cheap card table the minute they got you on the ropes. Nice.