Concordance Rate
Definition
In twin studies, the proportion of twin pairs in which both twins share a given trait or behaviour. Higher concordance in monozygotic (MZ) than dizygotic (DZ) twins is taken as evidence of a genetic contribution, though MZ twins also share more environmental features than DZ twins.
- Field
- Twin studies, behavioural genetics
- Definition
- Proportion of twin pairs sharing a trait
- Comparison groups
- Monozygotic (MZ) vs dizygotic (DZ) twins
- Interpretation
- Higher MZ than DZ concordance suggests genetic contribution
Common questions
Why can't a higher MZ concordance rate than DZ concordance rate be taken as proof of a purely genetic cause for criminal behaviour?+
MZ twins tend to share more of their environment than DZ twins, being treated more similarly by parents, peers and teachers and often spending more time together, so some of the extra concordance may reflect shared environment rather than shared genes. This confound is the standard criticism of twin-study evidence in criminology.
What does a low concordance rate even among monozygotic twins tell researchers?+
Since MZ twins share essentially all their genes, a concordance rate well below 100 percent for a trait like criminal offending shows that non-genetic factors, whether individual environment, chance, or gene-environment interaction, play a substantial role, meaning the trait is not fully determined by genotype alone.
Related terms
- Atavism
- Lombroso's concept that born criminals were evolutionary throwbacks to a more primitive human type, identifiable by physical stigmata. The concept is scientifically...
- Biosocial Criminology
- An approach that treats biological and social factors as mutually constitutive rather than alternative explanations for crime. It holds that genetic or...
- Gene-Environment Interaction (GxE)
- The phenomenon where a genetic predisposition is expressed differently depending on environmental context. A classic example is the MAOA-low variant, which correlates...
- Heritability
- The proportion of variation in a trait within a population that is attributable to genetic differences between individuals. A heritability estimate applies...
- Prefrontal Cortex (PFC)
- The frontal brain region responsible for impulse control, planning, and decision-making. Reduced grey matter volume and lower activation in the PFC have...