AC 2.1 - genetic theories of criminality

Question 1

Genetic theories of criminality

Answer 1

• Chromosomal disorders ( XYY theory / Jacob’s Syndrome & XXY theory / Klinefelter’s Syndrome)
• Twin studies
• Adoption studies

Question 2

What is XYY theory / Jacob’s Syndrome?

Answer 2

• Jacobs et al (1965)
• not inheritable

Question 3

What was the research method of XYY theory / Jacob’s Syndrome?

Answer 3

chromosome survey of 315 men at a maximum security hospital

Question 4

What were the findings of XYY theory / Jacob’s Syndrome?

Answer 4

• patients with criminal personalities had XYY chromosome
• concluded that men with XYY were more aggressive than XY

Question 5

What is the support of XYY theory / Jacob’s Syndrome?

Answer 5

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

Question 6

What is XXY theory / Klinefelter’s syndrome?

Answer 6

• Stockholm et al (2012)
• not directly inheritable

Question 7

What was the research method of XXY theory / Klinefelter’s syndrome?

Answer 7

compared 47 XXY to 47 XYY men using a statistical nationwide study

Question 8

What were the findings of XXY theory / Klinefelter’s syndrome?

Answer 8

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)

Question 9

What are monozygotic twins?

Answer 9

identical twins

Question 10

What are dizygotic twins?

Answer 10

non-identical twins

Question 11

What was the research method of lange’s twins’ study (1929)

Answer 11

compared rates of offending between 13 pairs of MZ twins and 17 pairs of DZ twins

Question 12

What were the findings of lange’s twins’ study (1929)?

Answer 12

• 10/13 MZ twins had been in prison
• 2/17 DZ twins had been in prison

Question 13

What were the conclusions of lange’s twins’ study (1929)?

Answer 13

MZ twins showed a higher concordance rate for criminal behaviour than DZ twins

Question 14

Christiansen (1997)

Answer 14

using data on over 3,500 twins, found concordance rates of 35% among male MZ twins compared with 13% more than DZ twins

Question 15

What was the support of Christiansen (1997)

Answer 15

Dalgard & Kringlen (1976) - Norwegian study that obtained similar results (MZ = 26% DZ= 15%)

Question 16

What is polygenic inheritance?

Answer 16

when one characteristic is controlled by 2 or more studies

Question 17

What is gene-environment interaction?

Answer 17

genes interact with the environment to produce criminal behaviour

Question 18

adoption studies

Answer 18

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

Question 19

What did Crowe (1972) find correlating criminality and genes?

Answer 19

• 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

Question 20

What did Hutchings & Mednick (1975) find correlating criminality and genes?

Answer 20

• 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

Question 21

What did Gabrielli & Mednick (1984) find correlating criminality and genes?

Answer 21

• Identified correlation between biological father convictions & child convictions for property offences
• evidence of gene-environment interaction

Question 22

What did Mednick et al (1987) find correlating criminality and genes?

Answer 22

• Many of the adoptees in this 14,000 strong Swedish sample had criminal biological parents
• strong correlations between sons & fathers