It seems to me that the experts are being awfully careless here. If a psychopath possesses glib and superficial charm, then Dennis Rader (the so-called BTK killer) does not quality. Neither was he parasitic, and he did not have many short-term marital relationships.

There is no doubt that there is something terribly wrong with the man. But "psychopath" is not the proper term for him, and a professional going public ought to know that.

As for the twin study described in the London Economist, how in the world could one apply the definition of psychopath to young children? Perhaps their empathy simply hasn't developed yet.

A teacher only sees the public face of a family. Perhaps the children they regard as psychopathic are abused at home, perhaps they live with someone insane, perhaps they are exposed to an unusual amount of violent media, perhaps their caregivers are giving them drugs...

My sister-in-law works in a children's hospital. It is not unusual for them to find illegal drugs in the blood of young children. Maybe the babysitter wants them to calm down... etc etc