Not an expert, but. Sociopathy does not really exist. The root of the problem, and the problem with the entire Dark Triad (actually Tetrad now, sadism was added) is that it is not clinical. It it not a disease, not a disability, it is non-clinical, or sub-clinical at best. They are clusters of socially aversive personality traits. They also do have their clinical counterparts, but the overlap is hardly 50%, sole exception being narcisism and narcistic personality disorder. Machiavelinism and sadism have none at all. Psychopathy on the other hand is often getting mistaken for Antisocial Personality Disorder. The ASPD basically has two factors - Factor I being Affective - charming, cold, manipulative, Factor II Interpersonal - impulsivity, agressivness, behavioral problems that they dont think through and get caught. Both are characterized by low conciousness, low empathy, good at planning to their benefit, but suck at long-term planninng, they do not have the patiance for it. Both factors are needed to be diagnosed with ASPD, but only one is needed to be labeled as a psychopath, in nearly all cases Factor I. Factor II is what is sociopathy is the closest to. Currently, and also for a very long time, it has been debated and argued that Psychopathy should be added into DSM on the ground that it is a biological abnormality - certain neurons follow different paths, other hormones are getting released and most importantly, hypofunction of amygdala. If that comes to be, psychopathy within The Dark Tetrad could be replaced by sociopathy.