Evaluate genetic explanation of offending behaviour

Limitation of twin studies is assuming equal environments

Often assumed that environmental factors are the same for MZ and DZ twins because they experience similar environments

However because MZ twins look identical people tend to treat them more similarly which in tern their behaviour

Therefore, higher concordance rates on MZ Maybe because they are treated more similarly than DZ suggesting conclusions lack validity

Strength is that it supports the diathesis-stress model of offending

Mednick et al studied 13,000 Danish adoptee having at least one court conviction.

Conviction rates

13.5% biological or adoptive parents had no convictions

20% one biological parent

24.5 both adoptive and biological parents

This data suggests that both genetic inheritance environment influences criminality Supporting the diathesis stress model of crime

Nature and nurture

Adoption study separate nature and nurture similarities due to biological parent can only be genetic

However many adoptions occur when children are older and adoptive maintain contact with biological family so still environmental influence

This suggests that adoption studies cannot fully separate Nature and nurture

Summary of the evaluation

Strength supports diathesis stress model

Limitation assumes equal environments of twins as monozygotic twins get treated the same which in tern affects behaviour and this lacks

Many adult days still maintain contact with biological family and adopted when they’re older so adoption studies cannot fully separate nature and nature