xyy genetic theory

• XYY syndrome

  a rare genetic condition that occurs when there is an error in cell division, resulting in a male being born with an extra y chromosome instead of the usual XY combination. physical symptoms include: fingers that curve inward, flat feet, widely larger head, taller height. developmental signs: delayed development of speech and language skills, attention deficit disorder, aggression, anxiety and autism spectrum disorder.
• more...

  the XYY chromosomal syndrome may act on the brains primitive drives including impulses towards violence, while triggering violent criminal acts. the condition was discovered in the 1960's. the claim is based on studies of imprisonment such as those in psychiatric hospitals, where a higher than average proportion of inmates were found to have XYY syndrome. many had histories of violent behaviour.
• 2 weaknesses

  • XYY is a rare condition, occurring in 1 to 1000 males. despite this, crime rates involving males are not rare, which means that XYY is not a common cause of crime. this suggests that other explanations need to be considered.
  • although XYY is a chromosome pattern found in some violent offenders, it is not possible to determine whether the XYY pattern caused them to commit crimes or not as there are other factors that influence behaviours such as moral upbringing, social and socio-economic factors.
• 1 strength

  price and whitmore found XYY males to be immature and unstable with a strong tendency to commit seemingly motiveless property crimes.
• 1 strength


  studies suggest that the lower intelligence of individuals with XYY syndrome, may be a factor that influences their criminality.
• 1 weakness

  XYY is a rare condition, occurring in 1 to 1000 males. despite this, crime rates involving males are not rare, which means that XYY is not a common cause of crime. this suggests that other explanations need to be considered.
• 1 weakness

  although XYY is a chromosome pattern found in some violent offenders, it is not possible to determine whether the XYY pattern caused them to commit crimes or not as there are other factors that influence behaviours such as moral upbringing, social and socio-economic factors.