biological explanations: genetic

Question 1

what do genetic explanations for crime suggest?

Answer 1

would-be offenders inherit a gene, or combination of genes, that predispose them to commit crime

Question 2

twin and adoption studies: christansen (1977)

Answer 2

• studied >3500 twin pairs in denmark
• found concordance rates for offender behaviour of 35% for MZ males and 13% for DZ males
• slightly lower rates for females

Question 3

how did christiansen (1977) check his data?

Answer 3

• included all twins born between 1880 and 1910 in a region of denmark
• offender behaviour was checked against danish police records

Question 4

what does christiansen (1977)’s data suggest?

Answer 4

it is not just the behaviour that might be inherited but the underlying predisposing traits

Question 5

twin and adoption studies: crowe (1972)

Answer 5

• found that adopted children whose biological mother had a criminal record had a 50% risk of having a criminal record by age 18
• adopted children whose biological mother didn’t have a criminal record had a 5% risk

Question 6

candidate genes: tiihonen et al. (2015)

Answer 6

• conducted a genetic analysis of almost 800 finnish offenders
• analysis found that about 5-10% of all severe violent crime in finland is attributable to the MAOA and CDH13 genotypes

Question 7

what are the 2 genes that may be associated with violent crime? (tiihonen et al. 2015)

Answer 7

• MAOA
• CDH13

Question 8

in what way the MAOA gene be associated with violent crime?

Answer 8

• regulates serotonin in the brain
• has been linked to aggressive behaviour

Question 9

in what way the CDH13 gene be associated with violent crime?

Answer 9

• linked to substance abuse
• linked to attention deficit hyperactivity disorder

Question 10

diathesis-stress model

Answer 10

• if genetics do have some influence on offending, it is likely that this is at least partly moderated by the effects of the environment
• a tendency towards offending behaviour may come through a combination of genetic predisposition and biological or psychological trigger
• eg. being raised in a dysfunctional environment, having criminal role models

Question 11

evaluation: using twin studies as genetic evidence assumes equal environments

Answer 11

• it is assumed by researchers studying twins that environmental factors are held constant because twins are brought up together and therefore must experience similar environments
• however, this ‘shared environment assumption’ may apply much more to MZ twins than DZ
• MZ twins look identical so people (especially parents) tend to treat them more similarly, which in turn affects their behaviour
• therefore, higher concordance rates for MZs in twin studies may simply be because they are treated much more similarly than DZ twins

Question 12

evaluation: support for diathesis-stress (mednick et al. 1984)

Answer 12

• studied 13,000 danish adoptees
• when neither the biological nor adoptive parents had convictions, 13.5% of adoptees did (quite high)
• when either of the biological parents had convictions, this rose to 20%
• when both adoptive and biological parents had convictions, it was 24.5%
• this shows that genetic inheritance plays an important role in offending but environmental influences are also important

Question 13

evaluation: nature vs. nurture

Answer 13

• it is presumed adoption studies (eg. mednick et al.) are a good way of separating nature and nurture
• if crime has a genetic component, then an adopted child should still experience the influence of the biological parent despite not living with them
• however, many adoptions take place when children are older, so they spend several years with their biological parents
• many adoptees are also encouraged to maintain contact with the biological family so biological parents exert an environmental influence