Twin theories

• Theory summary: crime is caused by genes. If one MZ twin has the gene for criminality and commits crime then so should the other twin
• Strength: MZ twins are identical so it makes sense to examine their offending rates
• Strength: Twin studies have given more explanation to genetic theories
• Limitation: If only genes caused crime then identical twins would show 100% concordance rate but studies show that it is less than 50%
• Limitation: It doesn't take into account identical twins sharing environment as environmental factors could produce similarities in behaviour
• Limitation: it is impossible to isolate and measure the effect of genes separately from environmental effects
• Limitation: In early studies there was no way of knowing if twins were identical due to a lack of DNA testing