AC 2.1 - genetic theories of criminality Flashcards
Biological theories of criminality
Genetic theories of criminality
- Chromosomal disorders ( XYY theory / Jacob’s Syndrome & XXY theory / Klinefelter’s Syndrome)
- Twin studies
- Adoption studies
What is XYY theory / Jacob’s Syndrome?
- Jacobs et al (1965)
- not inheritable
What was the research method of XYY theory / Jacob’s Syndrome?
chromosome survey of 315 men at a maximum security hospital
What were the findings of XYY theory / Jacob’s Syndrome?
- patients with criminal personalities had XYY chromosome
- concluded that men with XYY were more aggressive than XY
What is the support of XYY theory / Jacob’s Syndrome?
Birken et al (2006) = possibility of XYY chromosome abnormality in sexual offenders
- small scale study of 13 men sampled from 166 and 3 that had the XYY
- the presence of XYY defect has been raised as a defence in courts
What is XXY theory / Klinefelter’s syndrome?
- Stockholm et al (2012)
- not directly inheritable
What was the research method of XXY theory / Klinefelter’s syndrome?
compared 47 XXY to 47 XYY men using a statistical nationwide study
What were the findings of XXY theory / Klinefelter’s syndrome?
Men diagnosed with XXY & XYY were more frequently convicted for sexual abuse, burglary, and arson. Traffic offences were seen less in both groups compared to a control group of XY men which can be due to poor socioeconomic conditions (poor education)
What are monozygotic twins?
identical twins
What are dizygotic twins?
non-identical twins
What was the research method of lange’s twins’ study (1929)
compared rates of offending between 13 pairs of MZ twins and 17 pairs of DZ twins
What were the findings of lange’s twins’ study (1929)?
- 10/13 MZ twins had been in prison
- 2/17 DZ twins had been in prison
What were the conclusions of lange’s twins’ study (1929)?
MZ twins showed a higher concordance rate for criminal behaviour than DZ twins
Christiansen (1997)
using data on over 3,500 twins, found concordance rates of 35% among male MZ twins compared with 13% more than DZ twins
What was the support of Christiansen (1997)
Dalgard & Kringlen (1976) - Norwegian study that obtained similar results (MZ = 26% DZ= 15%)
What is polygenic inheritance?
when one characteristic is controlled by 2 or more studies
What is gene-environment interaction?
genes interact with the environment to produce criminal behaviour
adoption studies
If in criminal behaviour , the child is more similar to their biological parents than their adoptive parents. In which a genetic basis for criminality may be suggested
What did Crowe (1972) find correlating criminality and genes?
- where the biological mother had history of offending , the child had a 50% risk of acquiring one by the age of 18
- compared with a 5% risk were the biological mother didn’t have a criminal conviction
What did Hutchings & Mednick (1975) find correlating criminality and genes?
- of those sampled 21% of adopted boys went on to offend where the biological father had convictions
- increase to 36% of adoptees where both biological & adoptive fathers had criminal records
What did Gabrielli & Mednick (1984) find correlating criminality and genes?
- Identified correlation between biological father convictions & child convictions for property offences
- evidence of gene-environment interaction
What did Mednick et al (1987) find correlating criminality and genes?
- Many of the adoptees in this 14,000 strong Swedish sample had criminal biological parents
- strong correlations between sons & fathers
