Criminology is the science of criminal Behaviour. Larry J. Segal has written a great introductory criminology textbook and he has set out six major theories on why people commit crimes.

1. Rational Choice Theory

"According to the contemporary rational choice approach, law-violating behavior occurs when an offender decides to risk breaking the law after considering both personal factors (i.e., the need for money, revenge, thrills, and entertainment) and situational factors (i.e., how well a target is protected and the efficiency of the local police force). People who believe that the risks of crime outweigh the rewards may decide to go straight. If they think they are likely to be arrested and punished, they are more likely to seek treatment and turn their lives around than risk criminal activities."

Some examples include:

"Economic Opportunity Boston Magazine ran an article recently about a university lecturer with a master’s degree from Yale and a doctorate in cultural anthropology who took another job to pay the bills: call girl. Rather than living on the meager teaching salary she was offered, the “Ivy League hooker” chose to make the tax-free $140 per hour for her services (she charged $200, handing over $60 to the escort service that arranged her dates). She left the business when she became financially self-sufficient."

Theft: "For example, there are professional shoplifters, referred to as boosters, who use complex methods in order to avoid detection. They steal with the intention of reselling stolen merchandise to professional fences, another group of criminals who use cunning and rational decision making in their daily activities."

Drugs: "Research does in fact show that from its onset drug use is controlled by rational decision making. Users report that they begin taking drugs when they believe that the benefits of substance abuse outweigh its costs (e.g., they believe that drugs will provide a fun, exciting, thrilling experience)."

2. Biosocial Theory

"Rather than viewing the criminal as a person whose behavior is controlled solely by conditions determined at birth, most biocriminologists believe that physical, environmental, and social conditions work in concert to produce human behavior; this integrated approach is commonly referred to as biosocial theory."

Biochemical - "The major premise of the theory is that crime, especially violence, is a function of diet, vitamin intake, hormonal imbalance, or food allergies."

Neurological - "The major premise of the theory is that criminals and delinquents often suffer brain impairment, as measured by the EEG. Attention deficit hyperactivity disorder and minimal brain dysfunction are related to antisocial behavior."

Genetic - "The major premise of the theory is that criminal traits and predispositions are inherited. The criminality of parents can predict the delinquency of children."

Evolutionary - "The major premise of the theory is that as the human race evolved, traits and characteristics have become ingrained. Some of these traits make people aggressive and predisposed to commit crime."

3. Psychological Trait Theory

"...trait theories focuses on the psychological aspects of crime, including the associations among intelligence, personality, learning, and criminal behavior."

Psychodynamic - "The major premise of the theory is that the development of the unconscious personality early in childhood influences behavior for the rest of the person’s life. Criminals have weak egos and damaged personalities. The research focuses of the theory are on mental disorders, personality development, and unconscious motivations and drives.’ Such as a sociopath and psychopath. ..some psychologists distinguish between sociopaths and psychopaths, suggesting that the former are a product of a destructive home environment whereas the latter are a product of an inherited genetic defect."

Behavioral - "The major premise of the theory is that people commit crime when they model their behavior after others they see being rewarded for similar acts. Behavior is reinforced by rewards and extinguished by punishment."

Cognitive - "The major premise of the theory is that individual reasoning processes influence behavior. Reasoning is influenced by the way people perceive their environment. [Such as,] the child abuser perceives that he is superior and more important than others and hence is able to have sex with whomever and whenever he wants."

4. Neutralization Theory

"They view the process of becoming a criminal as a learning experience in which potential delinquents and criminals master techniques that enable them to counterbalance or neutralize conventional values and drift back and forth between illegitimate and conventional behavior. One reason this is possible is the subterranean value structure of American society. Subterranean values are morally tinged influences that have become entrenched in the culture but are publicly condemned. They exist side by side with conventional values and while condemned in public may be admired or practiced in private. Examples include viewing pornographic films, drinking alcohol to excess, and gambling on sporting events."

5. Hirschi’s Social Bond Theory

"[Hirschi] assumes that all individuals are potential law violators, but they are kept under control because they fear that illegal behavior will damage their relationships with friends, parents, neighbors, teachers, and employers. Without these social ties or bonds, and in the absence of sensitivity to and interest in others, a person is free to commit criminal acts."

6. Latent Trait Theory

"Their model assumes that a number of people in the population have a personal attribute or characteristic that controls their inclination or propensity to commit crimes. This disposition, or latent trait, may be either present at birth or established early in life, and it can remain stable over time. Suspected latent traits include defective intelligence, damaged or impulsive personality, genetic abnormalities, the physical-chemical functioning of the brain, and environmental influences on brain function such as drugs, chemicals, and injuries. Some latent trait theorists maintain that this master trait is inflexible, stable, and unchanging throughout a person’s lifetime, while others recognize that under some circumstances a latent trait can be altered, influenced, or changed by experiences and interactions."

An example includes impulsivity:

"Gottfredson and Hirschi trace the root cause of poor self-control to inadequate childrearing practices that begin soon after birth and can influence neural development. Once experiences are ingrained, the brain establishes a pattern of electrochemical activation that remains for life. Parents who refuse or are unable to monitor a child’s behavior, to recognize deviant behavior when it occurs, and to punish that behavior will produce children who lack self-control. In a sense, lack of self-control occurs naturally when steps are not taken to stop its development. These impulsive kids grow up to become poor parents, who use improper discipline, and produce another generation of impulsive kids."