[Spartacus]

Well, you could try, but do you really know fully how you behave?

Plus, the scores above proof that people don't answer accurately (consciously or not). A bunch of people that are 50 % psychopath? That's very rare.

Not fully definitely. In a sense yeah I have an idea of how I think I behave.

i'm sure you've heard of Johari Window. http://en.wikipedia.org/wiki/Johari_window

The concept is clearly related to the ideas propounded in the Myers-Briggs Type Indicator program, which in turn derive from theories about the personality first explored by psychologist Carl Jung.
Open or Arena: Adjectives that are selected by both the participant and his or her peers are placed into the Open or Arena quadrant. This quadrant represents traits of the subjects that both they and their peers are aware of.
Hidden or Façade: Adjectives selected only by subjects, but not by any of their peers, are placed into the Hidden or Façade quadrant, representing information about them their peers are unaware of. It is then up to the subject to disclose this information or not.
Blind Spot: Adjectives that are not selected by subjects but only by their peers are placed into the Blind Spot quadrant. These represent information that the subject is not aware of, but others are, and they can decide whether and how to inform the individual about these "blind spots".
Unknown: Adjectives that were not selected by either subjects or their peers remain in the Unknown quadrant, representing the participant's behaviors or motives that were not recognized by anyone participating. This may be because they do not apply or because there is collective ignorance of the existence of these traits. One facet of interest in this area is our human potential. Our potential is unknown to us, and others.

Probably there's something about myself that others see and I don't (blind spot).
Unknown sounds mysterious.

I'm not sure how accurate they make the study be. But what would someone with 50% psychopathic tendencies be capable of? Not sure what kind of results the researchers plan to get when they quantify it.