xyy theory

• chromosomes are tightly coiled dna molecules
• genes are section of DNA that code for particular characteristics
• chromosomes contain thousands of genes
• if you have XYY syndrome you have extra male sex chromosomes
• what does the xyy theory state ?

  since males are considered aggressive anyways it is believed men who have xyy syndrome are more aggressive than other men as they have more testosterone. XYY syndrome leads to high testosterone, powerful build, heightened aggression and tendency for violent crimes
• jacobs et al (1965)?

  found that 3% of men in prison had the XYY prison compared to the 0.1% in the general population
• criminals thought to have XYY syndrome ?

  john wayne gacey, arthur shawcross
• contradictory evidence ?

  testosterone and aggression levels amongst XYY men are no different to XY men. However, theyre at an increased risk of developmental delays and learning difficulties, its been found that theres a small assosciation between learning diffivulties and criminal behaviour
• iq of convicted offenders ir marginally lower than the general population
• Witkin et al ?

  concluded XYYs were often not good criminals as their low iq makes them more likely to be caught and convicted therefore explaining the dense XYY population in prisons
• critique ?

  reductionist- only considers the role of genetics influencing criminality