A psychopath is a person who has no conscience, has no fear, lacks emotions, and is virtually unable to have feelings, sympathy for or empathy with any other person.

They are also impulsive and egocentric, boastful and grandiose, and violate social,legal and moral norms whenever it suits them, while blaming others for their behaviour or denying it outright “It wasn't me, it was my evil twin”.

One psychopath working as a bartender killed a customer then claimed it was the customer's fault because “He should have seen I was in a bad mood”.

Psychiatrist Hervey Cleckley in a classic work, called The Mask of Sanity, observed that psychopaths, can seem quite normal and even superficially charming, hence the term "mask of sanity" describing the deceptive personality they present to the world. Robert Hare, inventor of the leading tool used to diagnose psychopathy calls them intraspecies predators, and it seems to me the mask of sanity is their camouflage.

Psychopaths with no other disorder do not exhibit grossly psychotic symptoms, such as hallucinations or delusions. But they lack empathy and guilt and are willing to manipulate, lie, or cheat with neither hesitation or remorse to achieve their own ends and are so abnormal in their interpersonal actions and behaviour that calling psychopathy a disorder seems justifiable.

Are psychopaths human? If the answer is no they are humanoid, like most aliens in Science Fiction films. Machine intelligence may exceed human intelligence at some point and a mechanical brain may be transplanted to a human body therefore we must consider whether psychopaths are human in the light the possibility of a non human intelligence in a human body. In the end however everyone must choose their own answer to this question. Personally I would argue that they are human but only just.

The ape closest to the hairless language using variety reading and that wrote this note, the Chimpanzee could be argued to have some, perhaps most of these characteristics. Chimpanzees lack empathy for other chimpanzees but do show fear: experiments showed that a chimpanzee, in a situation where they can feed themselves by pressing a lever and feed a chimpanzee in another cage by pressing a second lever presses the second lever randomly, but always feeds themselves, even if the other is a sibling.

A recognised test for psychopathy, known as the Hare test after its inventor, which has proven effective in revealing psychopathy in male criminals and psychiatric patients as well as in female criminals. The result of the test is a value on a continuum and suggests that everyone has some degree, however small, of psychopathy (have you never lied to save your skin, or pocketed excess change in a store without thinking the assistant might get it docked from their wages and then gone on your way whistling?). I think that on this scale the chimpanzee would be closer to the average human than is the classic psychopath.

Psychopathy is one member of the “Dark Triad” that also includes Narcissism and Machiavellanism and since all three share common traits, the assignment of the correct disorders to an individual is complicated. Care must also be taken to avoid labelling someone a psychopath simply because one dislikes them or their views and the tendency in the old Soviet Union (paralleled to a great extent in the USA, as I recall) of branding dissidents as insane shows how carefully the label “psychopath” must be used.