| What did Lange (1930) find? | 13 MZ twins and 17 DZ twins, where one of the had been to prison. 10/13 MZ twin pairs had both been to prison, compared to 2/17 DZ twins. |
| What did Christiansen (1977) find? | studied prison records and found a 33% concordance rate for MZ twins and 12% for DZ twins - but because the MZ genes aren’t 100%, it shows that it isn’t 100% genetic. |
| What are the 2 candinate genes? | Tiihonen et al (2014) after analysis of 900 offenders:
MAOA gene and CDH13 gene
Found that certain variations of both made individuals 13X more likley to have a history of violent disorders |
| What is the MAOA gene? | controls serotonin and dopamine and is linked to aggressive behaviour |
| What is the CDH13 gene? | Linked to substance abuse and ADHD |
| What is the antisocial personality disorder? | Lack of empathy, reduced emotional responses and implusive/irresponsible behaviour |
| What did Raine et al find? | Found a 11% reduction in volume of grey matter in the prefrontal cortex of people with APD - the region of the brain the regulates emotions |
| What did Keysers et al find? | Found that mirror neurons (controls empathy) might not always be turned on in people with APD.
Criminals only emphasised when asked to show an empathy reaction. Suggests they can ‘switch on/off’ empathy. |
| A strength of the genetic and neural explantion? | -Mixed research evidence from Mednick et al's resarch into 13,000 Danish approahces
-Analysis of criminal behaviour showed that when both the child's adopted and biological apretns have criminal convitions, 24.5% of the adopted children did too.
-Only 20% when just their biological parents had covictions and 13% when neither their adopted or biological parents had committed crimes
-This supports the diathesis-stress model, as it is clear there is a predisposition to crime as well the environment which the child is surrounded in. |
| A weakness of the genetic and neural approach? | -Methodological issues with twin studies used to support the genetic explanation of offending
-Lange's study into twins and criminality had one major flaw - he didn't know if the twins he was studing were identical, he guessed!
-Twin studies are unable to serpate genetics from environement as they are often brought up together in the same family and school envrionment
-Lowers internal validity, hard to establish cause and effect relationship with genetics and criminality due to confounding variables |
| A weakness of genetic and neural explanation? | -Criminality is complex and biological explanations can inappropriate or overly simplistic.
-Correlation-causation issue with the neural correlates explanation: did APD cause the biological deficit or vice versa?
-Don’t know that criminality has a biological cause. Overly reductionist approach – ignores higher level factors.
-Unlikely to be a ‘gene’ that causes criminality but can cause attitude changes and responses to social norms. Too reductionsit in their approach. |
