(checked) > a psychopath would keep his point after the challenge that depends on what that particular psychopath cared about as well as why he made the point to begin with. we can definitely use brain scans to detect specific aberrations of brain structure and activity that are extremely correlated with classical psychopathic behaviors. but a very small fraction of people who have these kinds of results when scanned aren't displaying classical behaviors of psychopaths. they can be prosocial (obviously it has to be beneficial to them). their thoughts are not like ours, however, and certainly their "feelings" (to the limited extent that they have any). scans in the future, along with genetic testing and analysis of "symptoms" (behaviours and thinking patterns), will help us to diagnose psychopathy. but it will likely become a spectrum of sorts.
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