Empathy is loosely thought to be the capacity to put yourself in another person's shoes. But this seems to be only one part of what constitutes empathy in relation to the psychopath. What is different about the psychopath is that he is unaffected or detached emotionally from the knowledge that he gains by putting himself in your shoes. Thus, although he is able to very quickly glean during the briefest encounter with another person a lot of very useful information about what makes that person tick, this knowledge is simply knowledge to be used or not as the psychopath chooses. What is missing in psychopaths is the compelling nature of the appropriate affective response to the knowledge gained from putting himself in another persons shoes, in the way that this happens in the normal person. This essential missing aspect of empathy, even in the severe psychopath, is not in my experience easily seen and one does not often get a second glimpse of it if one has been treated to a first one by mistake.

A rather crude example might suffice. A young psychopath who had inflicted multiple stab wounds on an elderly woman, and was charged with attempted murder, appeared subdued and appropriately sad about the offence during the early stages of a first interview. His eyes were moist as he accurately described how the woman must have felt during and after the attack. But later in the same interview, after good rapport had been established, this boy blurted out, "I don't know what all the fuss is about. The old bag only had a dozen scratches." To my knowledge, in all his subsequent years in the psychiatric hospital, he stuck to all the right lines of remorse which he quickly learned were more appropriate and useful. The bright psychopath, the experienced psychopath, doesn't stumble like that very often.

With luck and the right question about how the other person's feelings affected him there will be a barely perceptible pause, or a puzzled look, or even – rarely - the question, "How am I supposed to feel?"

Thus the second part of this two-part empathy in a psychopath is the choosing and acting of a script. Unlike the normal person, he can choose what script to follow. He is not compelled intuitively or automatically to react to the way he knows you feel. And unlike the normal person, he has been told, or learned by observing others, what he is supposed to feel.

As he rapes you or strangles you he is not compelled to feel your pain, your terror, your helplessness. There is no automatic, compelling, intuitive connection between what he knows you feel and what he feels. There is no way he must feel. Thus there is none of this kind of restraining force on his behavior. Therein lies the danger of psychopathy.

Are experiences in the first three years critical in developing this two-part type of empathy? Yes - if you accept that psychopathy can be created in the first three years.

For about half a century, we have known one unfailing recipe for creating psychopaths -- move a child through a dozen foster homes in the first three years. There are probably other things - genetic, organic, or biochemical, that can sometimes predispose a person to psychopathy. But that should not lull us into forgetting the one never-failing recipe. More importantly, we should be mindful that less severe disruptions of attachment, like a dozen different caregivers in the first three years can create partial psychopaths.

If we had an unfakable way to measure this two-part type of empathy we would be able to correlate such findings with clinical impressions of severity of psychopathy, whether we are speaking about psychopaths in prison, in politics, in business, or the day before they kill.