Often referred to 47 XYY as there is an error when cells divide that gives an extra chromosome
Some symptoms include;
Issues with speech
Higher likelihood of ADHD
Taller then average
Grow faster then average
Intelligence is often 10-15 IQ points lower than siblings
Impulsivity
Issues with speech can cause crime such as assault
Impulsivity can cause crime such as theft
Growing faster then usual can cause crime such as underage drinking
Other reasons for the crime associated with XXY can be due to socioeconomic standing ie; Nutrition, Education, Employment, Housing
Jacob supports XYY as they are overrepresented in prisons (15 in every 1000), shows that XYY may have a role in crime
Leggett found males with XYY has normal IQ's but speech difficulty so can affect child development, leading to crime
Stocholm found risk of conviction for XYY males is moderately increased but if socioeconomic factors are controlled then crime rates are similar to control sample without the extra Y chromosome. So crime may be connected to homelife rather then just XYY syndrome
Polman found playing violent games had a bigger influence on aggression levels in men than watching TV, showing crime is not due to XYY but due to observing and imitating violent behaviour