| Support for Diathesis-Stress Model – Sarnoff Mednick et al (1984) conducted study of 13,000 Danish adoptees. Researchers defined criminal behaviour as at least 1 court conviction, checked against Danish police records for each adoptee. If neither biological nor adopted parents had convictions = 13.5% criminal adoptees. Biological parent = 20%. Both adoptive and biological = 24.5%. Suggests role of both environmental and genetic influence.
Support for Genetic Influence – Brunner (1993) – studied 28 male members of Dutch family with history of impulsive and violent criminal behaviour, members of this family were likely to have deficiency of MAOA gene – supports idea of candidate genes. |
Twin Studies have low validity – (eg: Lange’s research poorly controlled, zygosity related to appearance rather than DNA testing), twins raised in same environment is a confounding variable, typically small sample meaning low internal validity, ineffective to base conclusions on.
Adoption studies may not be valid – late adoption means that biological parents influence may be difficult to measure, particularly if they still see their parents. Mednick’s study has low generalisability – does not account for violent crime or behaviours, only counts petty offences – conclusions drawn may not apply to more serious crimes. Biologically Deterministic – suggestion that crime is genetically or neutrally caused has implications in the legal system, raises ethical questions and takes away responsibility from criminals (link to Mednick et al – not all become criminals) Reductionist – Katz et al (2007) – crime runs in families, but so does emotional instability, mental illness and social deprivation – just genetic or neural effects are difficult to separate from other possible factors, overly simplistic to assume that crime is simply genetic or neural (in twin studies, MZ twins do not show 100% concordance) |