Biological Explanations of Criminal behaviour Brain dysfunction - implication of frontal lobe, hypothalamus, amygdala Genetics and neurotransmitter functioning - serotonin Gender and evolution

Biological explanations Innate factors predispose people to offend (genes, hormones, gender, evolution) Injury and illness may also shape behaviour

Brain dysfunction Raine et al (1997) http://www.youtube.com/watch?v=agPUoKB8eEk Raine et al (1997) Brain dysfunction

Brain dysfunction Research suggests that brain dysfunction may PREDISPOSE a person to being violent Violent offenders tend to have lower functioning brain activity The FRONTAL brain region may be associated with violent behaviour In addition reduced GLUCOSE METABOLISM has been implicated

Previous findings The role of the frontal cortex has been supported by many previous cases Phineas Gauge had a large iron rod driven through his frontal lobes - triggered high levels of aggression in his personality

Raine et al 1997- Brain abnormalities in murderers Investigated structural abnormalities in the brains of convicted murderers using PET scans. Found abnormal asymmetries in amygdala, thalamus and hippocampus in addition lowered glucose metabolism in the pre-frontal cortex

Raine et al (1997) Brain abnormalities in murderers PET scans showing ‘hot spots’ for cognitive activities

Read the text on Raine’s study and answer the following questions What was the aim of the study? Describe the sample used What were participants matched on? What was the PET scan used for? Specify the brain regions compared between the controls and the NGRI Describe the differences found between the control participants and NGRI. What did Raine conclude from the investigation? Identify 2 evaluative comments that can be made about the study

Brunner (1993) Genes & serotonin

How can we test if genes play a part in criminal behaviour? Twin studies: monozygotic twins (MZ-100%) dizygotic twins (DZ- 50%) Adoption studies: Find out the effects of genes and the environment Family studies: Study rates of schizophrenia in different relatives. E.g. compare concordance rates between mother and child.

Concordance rates What is a concordance rate? This is the coefficient value that is worked out by correlating the crime rate between 2 groups of people e.g. concordance between parent and child The correlation coefficient tell us the likelihood of both parent and child engaging in criminal behaviours The higher this number is the more chance there is of criminal behaviours developing This can then be represented as a percentage value. Christiansen (1977) found a 52% crime concordance in monozygotic twins and 22% in dizygotic twins

Brunner (1993) Brunner studied an abnormally violent large family in the Netherlands, collecting blood and urine samples from the 5 males as well as case study reports by the family He found that they all shared a deficit of the enzyme MAOA which is involved in serotonin metabolism – this was suggested to account for their violence

Testing Brunner’s theory To test the theory, they turned off the MAOA in mice and observed them to become fearless and impulsive, correlating with a 9-fold increase in serotonin levels

Problem with Brunner’s theory A problem was that most people with MAOA deficiency are not criminals Caspi (2002) did a study in NZ that found that it was a combination of childhood abuse and MAOA abnormality that produced the strongest predictor for aggression and criminal behaviour

Read the text on the Brunner study and then answer the following questions What was the aim of their study? Why was this particular sample selected? How was the data collected? Why was it necessary to collect samples over a 24 hour period? What does MAOA do? What does serotonin do and what is the associated issue with not having enough of it? How can we explain the fact that not all males in the family were violent yet they all shared the deficiency? What can we conclude form Brunner’s research? Write 3 evaluation points of this study?

Daly and Wilson (1985) Gender

Gender differences in criminal behaviors What gender differences can you think of in terms of criminal behaviour? Evolution of crime What is evolution, how can criminal behaviors be explained via evolutionary factors? What gender differences exist between males and females? Why do males tend to be involved in a lot more criminal activities than females? What advantages are there for risk taking behaviors?

Gender differences in criminal behaviors An organism’s ability to survive depends on how well its characteristics allow it to: Exploit the opportunities available in its environment Avoid or deal with the threats presented by its environment We call this the organism’s fitness The fitness of an individual will be directly influenced by their reproductive success.

Fitness

Fitness Yummy!

Gender differences in criminal behaviors Fit organisms are more likely to survive into adulthood than unfit ones. Consequently, they are more likely to mate and have offspring They pass on their genes to the next generation Gradually, the genes for successful characteristics spread through the population Risk taking behaviors may increase fitness in terms of predator avoidance and increased reproductive success.

Gender differences in criminal behaviors Pressures of mate selection in our evolutionary past have lead to different behaviors being pre-disposed in the population. Due to intersexual selection (choosing an appropriate mate) and intrasexual selection (competing for a mate) risky behaviors are exhibited by males to increased the likelihood of attracting a sexual partner. http://www.youtube.com/watch?v=voOjIPLxnoQ

Evolutionary differences in criminal behaviours Age crime curve- the peak of offending happens in early twenties and then falls into mid to late twenties. Why do you think that this age crime relationship exists?

Daly and Wilson- 2001. Key study Identified the ‘short term horizon’. Based on the idea that male seek immediate gratification- they are not concerned with long term gains. In terms of evolution what other reason could there be for risk taking behaviours if not for sexual selection processes?

Read the text on the Daly & Wilson study and then answer the following questions What was the aim of their study? How many community areas were involved? What is a correlational analysis? What variable did D & W correlate in their investigation? What was the average life expectancy of the participants? What did D & W find in relation to life expectancy and neighbourhood specific homicides? What was the co-efficient? They found a negative correlation between life expectancy and truancy from school- how was this explained? What problems may arise when using evolutionary explanations to explain modern day behaviours? What can we conclude form Daly’s research? Write 4 evaluation points of the biological explanations-single gene?, environmental influences?, falsifying evolution explanations?, methods of investigation?, reductionist?