Biological theories of crime
Genetic theories
Definition = criminality is passed down from the parents through genes
Twin studies – Christiansen
Tested the theory that crime is genetic, as monozygotic twins are fertilized from the same egg, if one is criminal
the other should be too.
Christiansen study on twins in Denmark
- MZ – 52% concordance rate
- DZ – 22% concordance rate
Ishikawa and Raine study concluded
- MZ – 44%
- DZ – 21.6%
Adoption studies - Mednik et al
If a child is born to criminal parents but adopted at a young age to non-criminals in an affluent area, will they
still become criminal – nature v nurture debate
important to the study that a child was adopted soon after birth so they wouldn’t have had influences from
both sides
Mednik et al – study on 14,000 boys in Denmark, concluded boys are more likely to become criminal if their
parents are
- 20% concordance rate between adopted child + birth parent
- 12.7% concordance rate between adopted child + adoptive parent
This showed how criminality may be influenced more by genetics rather than your environment
, XYY study - Jacob et al
In 1965 Jacob et al claimed that men with an extra Y chromosome (XYY) have super male syndrome, making
them more aggressive and violent than other males.
A study showed that the ratio of men in prison with XYY was:
15:1000 compared to
1:1000 in the general public
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