AC2.1-AC3.2 Flashcards
Biological Theories
Idea that physical characteristics can make people more likely to commit crime
Genetic theories
1700s
XYY theory, Twin studies, Adoption studies, Family studies
XYY theory
Jacob et al. (1965)
Suggests some crime may be due to chromosomal abnormality
Suggested that men with XYY syndrome are more aggressive than ‘XY’ men
Eg. serial killer John Wayne Gacy said to have XYY syndrome. SA, tortured and killed min 33 men in the USA
Jacob et al. Date
1965
Jacob et al. (1965)
XYY theory
Twin studies
Lange (1929)
• idea that a heritable trait may increase risk for criminal behaviour
• German physician found MZ twins higher degree than DZ twins for criminal behaviour
Christiansen (1977)
• Studied 3,000 + twin pairs
• found higher concordance for crime in male plus female MZ twins than DZ
MZ
Monozygotic
Identical Twins
100% DNA shared
DZ
Dizygotic
Twins from separate eggs
Share 50% of DNA
Lange (1929) and Christiansen (1977) both found
MZ twins showed a much higher degree of concordance than DZ twins for criminal behaviour
Twin studies study names
Lange (1929)
Christiansen (1977)
Lange (date)
1929
10/13 MZ twins convicted
2/17 DZ twins served time in prison
Christiansen (date.)
1977
3,000 + pairs of twins studied
(M) 35% (MZ) and 13% (DZ)
(F) 21% (MZ) and 8% (DZ)
Concordance rates
From Danish Islands
Adoption studies
Crowe (1972)
Found if adoptees bio mother had conviction they had a 50% chance of having a conviction
Found if adoptees bio mother didn’t have conviction only 5% of having conviction
Mednick et al. (1994)
Found no relationship criminal convictions of adoptive parents and their adopted children
Did find correlation convictions of bio parents and their bio kids
Crowe (date.)
1972.
If bio mother had conviction child had 50% chance
If bio mother didn’t child had 5% chance
(Adoption studies)
Mednick et al. (date.)
1994
Studied 14.000 adopted children
Found no correlation adoptive parents and kids
Found correlation bio parents and bio kids
Adoption Studies