How have twin studies been used to investigate genetic influences on criminality?

In the field of criminology, twin studies serve as a quasi-experimental method to investigate the extent to which genetic factors influence criminal behavior.12

Researchers utilize the biological differences between identical (monozygotic) and fraternal (dizygotic) twins to estimate the heritability of behavioral traits. Because identical twins share 100 percent of their genes while fraternal twins share, on average, only 50 percent, researchers compare concordance rates—the likelihood that both twins exhibit the same behavior—between the two groups.23

Studies have consistently found that identical twins are more likely to exhibit similar tendencies toward criminality than fraternal twins. This higher rate of concordance in identical pairs suggests that genetic influences play a role in criminal behavior. However, it is important to note that these biological factors do not absolutely determine whether an individual will commit a crime; rather, they may increase the susceptibility or risk of engaging in such behavior. Because environmental conditions can significantly influence the expression of these traits, the direction of causation remains complex and is often subject to the ongoing "nature-nurture" debate.12