Why does someone commit a crime while another person in almost exactly the same circumstances does not?
Is criminal behaviour caused by biology, personality, childhood experiences or the environment in which someone grows up? Do some people have characteristics that make them more likely to commit crime, or can ordinary people become involved in criminal behaviour because of the situations around them?
These are difficult questions, and psychologists have approached them from several different perspectives.
Criminal behaviour is not caused by one simple factor. Genetics, brain development, personality, learning, family relationships, peer influence, social circumstances and opportunities can all potentially play a role. This is why psychologists do not simply ask, “What makes a criminal?” Instead, they investigate the different factors that may contribute to criminal behaviour.
What is criminal behaviour?
Criminal behaviour refers to behaviour that breaks the law. However, what counts as a crime is not exactly the same in every country or historical period. Laws change, and behaviour considered illegal in one society may not be illegal in another.
This makes criminal psychology more complicated than simply identifying certain behaviours as “criminal.”
Psychologists are interested in questions such as why some individuals repeatedly offend, why people may become involved in crime during particular stages of their lives and what factors might increase or decrease the likelihood of offending.
Importantly, identifying a possible risk factor does not mean that the factor automatically causes someone to become a criminal.
For example, if research finds a relationship between childhood experiences and later offending, that does not mean that every person who experiences difficulties in childhood will commit a crime.
Human behaviour is influenced by multiple factors.
The biological explanation of criminal behaviour
One approach to criminal psychology looks at biology. Biological explanations suggest that characteristics of the brain, nervous system or genetics may influence behaviour.
One historical idea was that criminals could be identified by their physical appearance. This approach is associated with Cesare Lombroso, an Italian criminologist who argued in the nineteenth century that some criminals were “atavistic,” meaning they supposedly represented earlier stages of human evolution.
Lombroso believed that certain physical characteristics could indicate a tendency towards criminal behaviour. His ideas included features such as particular facial structures, large jaws and other physical characteristics.
Today, Lombroso's theory is regarded as scientifically problematic. Criminal behaviour cannot reliably be identified simply by looking at someone's physical appearance.
However, his work is historically important because it represents one of the early attempts to explain crime scientifically. Modern biological psychology takes a very different approach. Rather than examining someone's appearance, researchers investigate factors such as genes, brain structure, neurotransmitters and physiological responses.
Genetics and criminal behaviour
Could criminal behaviour partly have a genetic component?
This is a difficult question because criminal behaviour is not controlled by a single “crime gene.”
Instead, researchers have investigated whether certain genetic characteristics might increase vulnerability to behaviours associated with aggression, impulsivity or poor emotional regulation.
Twin studies are sometimes used to investigate the possible influence of genetics. Identical twins share almost all of their genes, whereas non-identical twins share roughly half of their genetic variation, on average.
If identical twins were consistently more similar in criminal behaviour than non-identical twins, researchers might consider this evidence that genetic factors contribute to offending.
However, twin studies have limitations. Identical twins often share more than just their genes. They may experience similar parenting, schools, social environments and expectations.
Therefore, differences or similarities between twins cannot automatically be attributed entirely to genetics. This is one reason psychologists increasingly recognise the importance of nature and nurture interacting with each other.
The role of the brain
Another biological explanation focuses on brain functioning. Areas of the brain involved in emotional regulation, decision-making and impulse control may be relevant to criminal behaviour.
The prefrontal cortex, for example, is involved in functions such as planning, decision-making and controlling behaviour.
The amygdala plays an important role in processing emotional information, including fear and threats.
Researchers have investigated whether differences in brain functioning may be associated with aggression and antisocial behaviour. However, having a particular brain characteristic does not mean that someone will inevitably commit a crime.
The relationship between biology and behaviour is much more complicated. Brain development is influenced by experience, environment and other biological factors. Therefore, modern explanations generally avoid the idea that biology completely determines behaviour.
The psychological explanation: personality
Psychologists have also investigated whether certain personality characteristics are associated with criminal behaviour. One important example is Eysenck's theory of personality.
Hans Eysenck suggested that personality can be described using dimensions including extraversion, neuroticism and psychoticism. According to Eysenck, people with high levels of psychoticism may be more likely to display characteristics such as aggression, hostility and impulsivity.
Eysenck suggested that personality characteristics could interact with conditioning and socialisation. For example, children who are naturally more impulsive may find it more difficult to learn to control their behaviour through punishment and social expectations. This could potentially make antisocial behaviour more likely.
However, personality alone cannot explain every criminal act. People with similar personality characteristics can behave very differently depending on their circumstances.
The role of learning
Another important psychological explanation is that criminal behaviour can be learned. This idea is strongly associated with Albert Bandura's Social Learning Theory.
Bandura argued that people can learn behaviours by observing others. This process is known as observational learning or modelling. A person does not necessarily have to experience a behaviour themselves to learn it.
They can observe another person performing the behaviour and then imitate it. This becomes particularly important when the behaviour appears to be rewarded.
Social Learning Theory and crime
Imagine a child grows up around people who regularly use aggression to solve conflicts. If the child observes that aggressive behaviour allows someone to get what they want, they may learn that aggression is an effective strategy. If other people praise or reward the behaviour, the child may be even more likely to imitate it.
This can create a cycle: Observation → imitation → reinforcement → repeated behaviour
The child may also develop beliefs about what behaviour is considered normal.
If criminal behaviour is repeatedly presented as acceptable or rewarding, the individual may become less likely to view it as unacceptable. This does not mean that children automatically copy everything they see.
Bandura's theory emphasises factors such as attention, motivation and whether the observed behaviour appears to have positive or negative consequences.
Bandura's Bobo doll study
One of the most famous studies associated with Social Learning Theory is Bandura, Ross and Ross's Bobo doll experiment. Children observed adults behaving aggressively towards a large inflatable Bobo doll.
The children were then placed in a situation where they could interact with the doll themselves. Some children reproduced aggressive behaviours they had observed.
The study provided evidence that children can learn aggressive behaviour through observation. However, the Bobo doll study was not a study of criminal behaviour itself.
It demonstrated that aggression could be learned through modelling. Psychologists can therefore use it to help explain one possible mechanism through which antisocial behaviour might develop.
The role of reinforcement
Social Learning Theory also highlights reinforcement. Suppose someone commits a crime and receives money as a result.The financial reward may reinforce the behaviour.
If they commit another offence and experience the same reward, the behaviour may become more likely to continue. This is known as positive reinforcement because something desirable is added following the behaviour.
However, reinforcement can also occur socially. A person might receive status, respect or approval from members of a peer group after participating in antisocial behaviour. This could make the behaviour more likely to continue.
The social environment
Criminal behaviour cannot be understood entirely through biology or individual personality. The social environment can also influence behaviour.
People are influenced by their families, friends, schools, communities and wider culture.Peer groups can be particularly important.
A teenager who spends significant amounts of time with peers who regularly engage in criminal behaviour may encounter more opportunities and encouragement to participate.
This does not mean that having friends who offend automatically causes someone to offend. It simply illustrates how behaviour can be influenced by the people around us.
The role of family and childhood experiences
Researchers have also investigated the relationship between childhood experiences and later antisocial behaviour.
Factors such as inconsistent discipline, family conflict, neglect and exposure to violence have been investigated as potential risk factors.
One possible explanation is that children learn behavioural patterns from their surroundings. A child who repeatedly sees aggression being used to solve problems may learn that aggression is an acceptable way to respond to conflict.
However, it is important not to assume that difficult childhood experiences inevitably produce criminal behaviour. Many people experience significant adversity and do not become offenders.
Protective factors, supportive relationships and individual differences can all influence development.
Nature versus nurture
Criminal psychology provides an excellent example of the classic nature versus nurture debate.
Nature refers to biological influences such as genetics and brain development while nurture refers to environmental influences such as family, education, peers and life experiences.
The evidence increasingly suggests that behaviour cannot simply be placed into one category. Genes may influence characteristics such as temperament, but the environment can influence how those characteristics develop.
For example, someone may have a naturally impulsive temperament, but supportive parenting and a positive environment could help them develop effective ways of managing their behaviour.
Another person with similar biological characteristics may grow up in a very different environment. Their behavioural development could therefore be different. This interaction is often described as gene–environment interaction.
Why do people stop offending?
Understanding criminal behaviour also means asking the opposite question: Why don't people continue committing crimes?
People can change.
As individuals grow older, their priorities may change. They may develop stronger relationships, find employment, become parents, leave harmful peer groups or develop better emotional regulation.
The consequences of offending may also discourage future behaviour. This is important because criminal behaviour is not necessarily a fixed characteristic of someone's personality. A person may offend at one point in their life and later stop.
Psychologists therefore study both the factors associated with offending and the factors associated with desistance, which means stopping criminal behaviour.
Can psychology help prevent crime?
Psychological research can potentially contribute to crime prevention. If researchers understand factors associated with offending, interventions can be designed to address some of those factors.
For example, programmes may focus on: improving emotional regulation, developing problem-solving skills, challenging harmful beliefs, improving family relationships, reducing exposure to harmful peer influence and developing educational and employment opportunities.
The aim is not simply to punish criminal behaviour but, where appropriate, to understand some of the factors that contribute to it. Psychological approaches can therefore play a role in rehabilitation.
Evaluating psychological explanations of crime
One strength of psychological explanations is that they recognise that behaviour is complex. Social Learning Theory, for example, can explain how behaviour may be acquired through observation and reinforcement.
Biological approaches can help researchers investigate the relationship between brain development, genetics and behaviour. Personality theories can help explain individual differences.
However, each approach has limitations when considered on its own. A biological explanation may underestimate the influence of social and environmental factors. A psychological explanation may overlook biological influences. A social explanation may struggle to explain why people exposed to similar environments can behave very differently.
This suggests that criminal behaviour is better understood as the result of multiple interacting factors rather than one simple cause.
Does having a risk factor mean someone will become a criminal?
This is one of the most important ideas to understand when studying criminal psychology. Suppose research finds an association between a particular childhood experience and later offending. It would be incorrect to conclude that every person with that experience will become a criminal.
A risk factor increases the possibility of a particular outcome; it does not guarantee it. Similarly, a biological characteristic associated with aggression does not mean that a person is destined to become violent.
Human behaviour involves choices, circumstances, learning, relationships and many other factors. Psychological research therefore needs to be interpreted carefully.