The psychological trait theory focuses on all of the mental aspects of why someone commits a crime, and associates it with their intelligence, personality, learning, and criminal behavior. Within this theory are three sub-theories, the psychodynamic theory, the behavioral theory, and the cognitive theory. As well, there are two traits which lend to the beliefs in this theory, the personality trait, and the intelligence trait.
The psychodynamic theory was developed by Sigmund Freud. According to this theory, the human mind performs three main functions. These are the conscious, the preconscious, and the unconscious. The unconscious mind controls every day thoughts and the waking mind. The preconscious mind controls the elements of experience that are out of awareness but can be brought back at any time, such as memories. The unconscious mind controls the body's biological desires, that cannot be easily expressed as everyday conscious thoughts. Many people repress these strong feelings of sex and hostility, causing them to act on them at a later time. Freud also believed in the id, ego, and superego dynamics of the human mind. The id is the primitive biological drives that are present within everyone at birth. The ego is the part of the mind that develops in early childhood, and controls the basic instincts that cannot be instantly gratified. The superego is the aspect of the mind that develops as a result of incorporating the moral standards and values of the family, community, etc.
The behavioral theory states that human actions are developed through learning experiences. This theory relies on the behaviors of people that they engage in during their everyday lives. It views crime as learned responses to life situations, and does not view it as necessarily abnormal or morally immature to respond in such a way. The most relevant theory to criminology under the behavioral theory is the social learning theory. This theory states that people are not born with the ability to act violent, and rather, they learn from previous life experiences to act violent. Their behavior is generally modeled after three sources— the family, environmental experiences, and the mass media.
The cognitive theory focuses on how people perceive and mentally represent the world around them. According to Lawrence Kohlberg, there are six stages of mental development. The first one is that the "right" thing to do is obedience of power and the avoidance of punishment. The second is that "right" is taking responsibility for oneself, meeting one's own needs, and leaving others to take responsibility for themselves. The third stage is that "right" is being good in the sense of having good motives, having concern for others, and "putting yourself in the other person's shoes". The fourth stage is that "right" is maintaining the rules of society and serving the welfare of the group or society. The fifth stage is that "right" is based on recognizing individual rights within a society, with agreed upon rules. The sixth stage of "right" is an assumed obligation to principles applying to all humankind, such as justice, equality, and respect for human life. As well, Kohlberg noticed that criminals were found to be lower in their moral judgement than non-criminals. In general, people who obey the law in order to avoid punishment or to serve themselves are more likely to commit crimes than anyone else.
Also under the psychological theory, personality plays a big role in whether or not a person commits a crime. Some personality traits that lead to a life of crime can include self- assertiveness, defiance, extraversion, ambivalence, impulsiveness, narcissism, suspicion, sadism, lack of concern for others, feeling unappreciated, distrust of authority, poor personal skills, mental instability, hostility, and resentment.