In 1879 psychology was established as a scientific discipline. Psychology emerged at a same time as criminology. The father of psychology was a German psychologist Wilhelm Wundt. Scientific methodologies, which were implemented in biological theories had many flaws, and the task was given to psychology to explain criminal behavior Theories to explain criminal behavior existed throughout history, but what is different about is that psychological theories include research of cognitive thinking or decision making processes that could explain why people choose to break a law in a particular situation. In general terms, psychologists are committed to the scientific study of human behavior, with its emphasis on hypotheses that can be tested using empirical and quantitative data in well controlled experiments and making systematic observation of experimental variables how they effect on the outcome of the experiment. Psychology has been significant to understanding criminal responsibility for many decades. It offers several different explanations, reasons and motives of crime, which are behind the criminal actions. In order to make any definitive conclusion on any theories it is required to analyze them and their contribution in criminology.

In psychology, there are two areas of research: behavior observation and behavior prediction. Psychological theories of delinquency sought abnormalities in behavior or  personality of criminals.
The term psychology was coined by Marko Marulic (father of Croatian literature) in his work "Psichiologia de ratione anime humanae" (1510-1517).

Personality theories of delinquency

Psychoanalytical theory developed by Sigmund Freud (1856-1939) stated that human personality has three psychic structures: id, ego and super ego. Id is an instance of personality who pursues instant needs without any thought and analysis. Ego is the instance which is a result of education and socialization, while super ego psychic instance is a container of all messages received from parents. Therefore, crime is a result of Id's prevalence over superego.
Although crime theory was only partially mentioned in a Freud's theory, psychoanalytical theory became the popular explanation of crime, especially when motives of  delinquent behavior couldn't be explained.

"Some people cannot be bought by gold or jewels. They just want to see the world burn."

Instinctive theories of delinquency

According to Freud, there are two instincts: eros and thanatos. Eros is a desire to live, while thanatos is a desire to die. Constant struggle exists between eros and thanatos. Aggressiveness must be blown out through sport or physical exercise, because if not it could result with inadequate social behavior like violence or suicide. Individuals are often balancing between eros and thanatos.

Eysenck's theory of crime: Extroversion and introversion

Eysenck claimed that the hedonistic tendency to commit crimes is controlled by the conscience. He also spoke about introversion and extroversion. Introverted persons are sensitive and can't take the limited number of  stimulus, while extroverted persons enjoy in a large number of stimulus and do not to be bored. According to Eysenck, criminality is a natural and normal choice with whom the people enhance pleasure or reduce pain. Reactions on some behavior are punishments or rewards. Extroverted persons aren't able to learn from experience.
Other psychological theories of the crime deal with mental disorders, psychopathy, self induced mental incapacity (alcoholism and drug addiction) and influence of public media on the crime. Today, personality test are able to provide a great insight about someones predisposition towards delinquency by examining the potential conflicts, which exist in someones personality.

Research of iq relation to crime