Biological Explanations: Criminal Behaviours

Genetic factors may predispose individuals to criminal behavior.
Twin studies show higher concordance rates for delinquent behavior in MZ twins (52%) compared to DZ twins (21%).
Two genes linked to criminal behavior: monoamine oxidase A (MAOA) and Cadherin 13 (CDH13).
Low MAOA activity, known as the 'warrior gene', linked to violent behavior.
Tihonen et al. (2015) found that 5-10% of violent crime in Finland is due to abnormalities in MAOA and CDH13 genes.
Diathesis-stress model: genes are switched on/off by epigenomes affected by environmental factors.
Caspi et al. (2002) found that 12% of men with low MAOA gene experienced maltreatment and were responsible for 44% of violent convictions.
Raine (2004) found reduced functioning in the prefrontal cortex of murderers, psychopaths, and violent individuals.
Low serotonin levels may predispose individuals to impulsive aggression, while dopamine hyperactivity may enhance this effect.
Both very high and very low levels of noradrenaline have been associated with aggression, violence, and criminality.

Some people inherit types of behavior that predispose them to behaving in a criminal way.

Genetic engineering could alter an individual's genetic composition to eradicate undesirable traits.
Replacing a defective MAOA gene with a ‘normal’ one in a fertilized ovum could be possible.

Adoption studies: Crowe (1972) found adopted children with criminal biological parents had a 38% higher chance of developing a criminal record.
Mednick et al. (1987) found 20% of adoptees with criminal biological parents became criminals, compared to 15% adopted into criminal families.
Genetic links: Variations in the MAOA gene are linked to increased aggression and impulsivity.
Blonigen et al. (2005) found genetic links to psychopathy and violent tendencies, but non-violent crimes lack clear genetic explanations.
Findlay (2011) argues crime is socially constructed and includes many different behaviors.
Tihonen et al. (2015) found individuals with a defective gene were 13 times more likely to commit repeated violent crimes, but not all carriers became criminals.
Caspi et al. demonstrated gene-environment interactions influencing behavior.

The amygdala is located in the medial temporal lobe of the brain and is part of the limbic system.
It is highly connected to the hypothalamus, hippocampus, and prefrontal cortex.
It plays a major role in assessing and responding to environmental threats.
Coccaro et al. (2007) found that participants with intermittent explosive disorder (IED) showed high levels of amygdala activity when viewing angry faces.
Yu Gao et al. (2010) proposed that amygdala dysfunction disrupts fear conditioning, leading to fearless, aggressive, and antisocial behavior.
Longitudinal study: Participants tested for fear conditioning at age three; those who committed crimes at age 23 had shown no fear conditioning when they were three years old.

Gospic et al. (2011) found that rejection of unfair offers was associated with heightened amygdala activity.
Administering a sedative drug reduced both aggression and amygdala activity.
Pardini et al. (2014) tracked males over 20 years and found that those with high aggression had smaller amygdala volumes.
Raine et al. (1997) studied murderers and found increased amygdala activity but decreased activity in the orbitofrontal cortex (OFC).
The amygdala regulates fear and anxiety, and damage impairs processing of these emotions, reducing empathy and social functioning.