The American Psychiatric Association defines a sociopath as follows:
Antisocial personality disorder is characterized by a lack of regard for the moral or legal standards in the local culture. There is a marked inability to get along with others or abide by societal rules. Individuals with this disorder are sometimes called psychopaths or sociopaths.
Diagnostic Criteria (DSM-IV)
1. Since the age of fifteen there has been a disregard for and violation of the right's of others, those right's considered normal by the local culture, as indicated by at least three of the following:
A. Repeated acts that could lead to arrest.
B. Conning for pleasure or profit, repeated lying, or the use of aliases.
C. Failure to plan ahead or being impulsive.
D. Repeated assaults on others.
E. Reckless when it comes to their or others safety.
F. Poor work behavior or failure to honor financial obligations.
G. Rationalizing the pain they inflict on others.
2. At least eighteen years in age.
3. Evidence of a Conduct Disorder, with its onset before the age of fifteen.
4. Symptoms not due to another mental disorder.
This definition doesn't quite tell the whole story, though. Sociopaths are often disguised as ordinary, even likable people; but a closer look at their lives shows that they often cause heartbreak and catastrophe to anyone who makes the fatal error of getting close to them.
People with this disorder appear to be charming at times, and make relationships, but to them, these are relationships in name only. They are ended whenever necessary or when it suits them, and the relationships are without depth or meaning, including marriages. They seem to have an innate ability to find the weakness in people, and are ready to use these weaknesses to their own ends through deceit, manipulation, or intimidation, and gain pleasure from doing so.
In short, sociopaths are like a person who lives inside a room full of mirrors. They are motivated by their own needs and feelings and only interact with other individuals as a means to gaining something that they feel they need. They have no regard for the other person's feelings or consequences beyond their own personal goals.
Romantically, they can be charming, give flattering comments and do little favors and give apparent undivided attention -- all the activities that we usually associate with someone who is kind and loving. But these are just learned behavior -- a means to an end -- and disguise the fact that the sociopath has no feeling of empathy or love, as most people know it.
Taken to the extreme, a sociopath is capable of murder, rape and violence. They can beat up an old woman, abuse a child or kill students in a classroom with calm, calculating precision. They simply do not feel the sense of right or wrong, or compassion. To the sociopath, these concepts are intellectual -- not emotional.
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Would also like to add that a sociopath can pass lie detector test, can the sociopath fool psychiatrists?