There are genes that lead to particular traits and characteristics that increase the probability of criminal behavior. Both genes and environment are important to behavior. Psychopathy is defined as antisocial behavior that is considered primarily genetic in origin. Sociopath is antisocial behavior that is mostly environmental in origin. The most common features of a psychopath are inability to profit from experience or form meaningful relationships, lack of impulse control and moral sense, emotionally immature, and unable to experience feelings of guilt. Active gene/environment correlation refers to the seeking of an environment compatible with genetic disposition. Reward dominance, or BAS/BIS theory, is a neurological theory of psychopathy and criminal behavior based on the proposition that behavior is regulated by two opposing mechanisms, the behavioral activating system (BAS) and the behavioral inhibition system (BIS). The BAS motivates one to pursue things that are rewarding, the BIS prevents one from going too far in that pursuit. The fight/flight system (FFS) has been added to the BAS/BIS model, and is a subsystem of the autonomic nervous system specializing in responding to threats. Just as individuals differ in terms of BAS/BIS functioning, they differ in terms of FFS arousal, most having a system that is neither too active nor too sluggish. Suboptimal arousal theory is based on the finding that different levels of neurological arousal correlate with different personality and behavioral patterns. This states that in the range of everyday situations, the level of stimulation most people find optimal, some find boring, and others find uncomfortably overstimulating. Cheater theory is based on evolution by natural selection. A small percentage of males do not abide by normal courtship rules of the species and achieve sexual intercourse by coercive and/or sneaky tactics. This applies to any sort of behavior, not just sexual behavior, because the traits useful for pursuing also are useful in following a criminal strategy. Prefrontal dysfunction theory and the possible influence of child abuse and neglect on the structure and functioning of the brain are discussed. 65 references, 1 figure