Biological Explanations of Criminal behaviour

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 DYSFUNCTIONBRAIN DYSFUNCTIONRaine et al (1997)Raine et al (1997)

http://www.youtube.com/watch?v=agPUoKB8eEk

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 pervious cases Phineas Gauge had a

large iron rod driven through his frontal lobs - 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

PET scans showing ‘hot spots’ for cognitive activities

Raine et al (1997) Brain abnormalities in murderers

Read the text on Raine’s study and answer the following questions

1. What was the aim of the study?2. Describe the sample used3. What were participants matched on?4. What was the PET scan used for?5. Specify the brain regions compared

between the controls and the NGRI6. Describe the differences found between

the control participants and NGRI. 7. What did Raine conclude from the

investigation?8. Identify 2 evaluative comments that can

be made about the study

GENES & SEROTONINGENES & SEROTONINBrunner (1993)Brunner (1993)

How can we test if genes play a part in criminal How can we test if genes play a part in criminal behaviour?behaviour?

Twin studies: Twin studies: monozygotic twins (MZ-100%)monozygotic twins (MZ-100%) dizygotic twins (DZ- 50%)dizygotic twins (DZ- 50%)

Adoption studies:Adoption studies: Find out the effects of genes and the environmentFind out the effects of genes and the environment

Family studies:Family studies: Study rates of schizophrenia in different relatives. Study rates of schizophrenia in different relatives.

E.g. compare concordance rates between mother and E.g. compare concordance rates between mother and child. child.

Concordance ratesConcordance rates

What is a concordance rate? What is a concordance rate?

This is the coefficient value that is worked out by correlating the This is the coefficient value that is worked out by correlating the crime rate between 2 groups of people e.g. concordance between crime rate between 2 groups of people e.g. concordance between parent and childparent and child

The correlation coefficient tell us the likelihood of both parent and The correlation coefficient tell us the likelihood of both parent and child engaging in criminal behaviourschild engaging in criminal behaviours

The higher this number is the more chance there is of criminal The higher this number is the more chance there is of criminal behaviours developingbehaviours developing

This can then be represented as a percentage value. This can then be represented as a percentage value.

Christiansen (1977) found a 52% crime Christiansen (1977) found a 52% crime concordance in monozygotic twins and 22% in concordance in monozygotic twins and 22% in dizygotic twinsdizygotic twins

Brunner (1993)Brunner (1993)

Brunner studied an abnormally violent Brunner studied an abnormally violent large family in the Netherlands, collecting large family in the Netherlands, collecting blood and urine samples from the 5 males blood and urine samples from the 5 males as well as case study reports by the familyas well as case study reports by the family

He found that they all shared a deficit of He found that they all shared a deficit of the enzyme MAOA which is involved in the enzyme MAOA which is involved in serotonin metabolism – this was serotonin metabolism – this was suggested to account for their violencesuggested to account for their violence

Testing Brunner’s theoryTesting Brunner’s theory

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

Problem with Brunner’s theoryProblem with Brunner’s theory

A problem was that most people with A problem was that most people with MAOA deficiency are not criminalsMAOA deficiency are not criminals

Caspi (2002) did a study in NZ that found Caspi (2002) did a study in NZ that found that it was a combination of childhood that it was a combination of childhood abuse and MAOA abnormality that abuse and MAOA abnormality that produced the strongest predictor for produced the strongest predictor for aggression and criminal behaviouraggression and criminal behaviour

Read the text on the Brunner study and then Read the text on the Brunner study and then answer the following questionsanswer the following questions

1.1. What was the aim of their study?What was the aim of their study?

2.2. Why was this particular sample selected?Why was this particular sample selected?

3.3. How was the data collected?How was the data collected?

4.4. Why was it necessary to collect samples over a 24 hour Why was it necessary to collect samples over a 24 hour period? period?

5.5. What does MAOA do?What does MAOA do?

6.6. What does serotonin do and what is the associated issue What does serotonin do and what is the associated issue with not having enough of it? with not having enough of it?

7.7. How can we explain the fact that not all males in the family How can we explain the fact that not all males in the family were violent yet they all shared the deficiency? were violent yet they all shared the deficiency?

8.8. What can we conclude form Brunner’s research?What can we conclude form Brunner’s research?

9.9. Write 3 evaluation points of this study? Write 3 evaluation points of this study?

GENDERGENDERDaly and Wilson (1985)Daly and Wilson (1985)

Gender differences in Gender differences in criminal behaviorscriminal behaviors

What gender differences can you think of in terms What gender differences can you think of in terms of criminal behaviour? of criminal behaviour?

Evolution of crime Evolution of crime What is evolution, how can criminal behaviors What is evolution, how can criminal behaviors

be explained via evolutionary factors?be explained via evolutionary factors? What gender differences exist between males and What gender differences exist between males and

females?females? Why do males tend to be involved in a lot more Why do males tend to be involved in a lot more

criminal activities than females?criminal activities than females? What advantages are there for risk taking What advantages are there for risk taking

behaviors? behaviors?


An organismAn organism’’s ability to survive depends s ability to survive depends on how well its characteristics allow it to:on how well its characteristics allow it to:Exploit the opportunities available in its Exploit the opportunities available in its

environmentenvironmentAvoid or deal with the threats presented Avoid or deal with the threats presented

by its environmentby its environment We call this the organismWe call this the organism’’s s fitnessfitness The fitness of an individual will be directly The fitness of an individual will be directly

influenced by their reproductive success. influenced by their reproductive success.

FitnessFitness

FitnessFitness

Yummy!


Fit organisms are more likely to survive into Fit organisms are more likely to survive into adulthood than unfit ones.adulthood than unfit ones. Consequently, they are more likely to mate Consequently, they are more likely to mate

and have offspringand have offspring They pass on their genes to the next They pass on their genes to the next

generationgeneration Gradually, the genes for successful Gradually, the genes for successful

characteristics spread through the populationcharacteristics spread through the population Risk taking behaviors may increase fitness in Risk taking behaviors may increase fitness in

terms of predator avoidance and increased terms of predator avoidance and increased reproductive success. reproductive success.


Pressures of mate selection in our Pressures of mate selection in our evolutionary past have lead to different evolutionary past have lead to different behaviors being pre-disposed in the behaviors being pre-disposed in the population. population.

Due to intersexual selection (choosing an Due to intersexual selection (choosing an appropriate mate) and intrasexual selection appropriate mate) and intrasexual selection (competing for a mate) risky behaviors are (competing for a mate) risky behaviors are exhibited by males to increased the exhibited by males to increased the likelihood of attracting a sexual partner. likelihood of attracting a sexual partner.

http://www.youtube.com/watch?v=voOjIPLxnoQ

Evolutionary differences in Evolutionary differences in criminal behaviourscriminal behaviours

Age crime Age crime curve- the peak curve- the peak of offending of offending happens in happens in early twenties early twenties and then falls and then falls into mid to late into mid to late twenties. twenties.

Why do you Why do you think that this think that this age crime age crime relationship relationship exists? exists?

Daly and Wilson- 2001. Key studyDaly and Wilson- 2001. Key study

Identified the ‘short term horizon’. Identified the ‘short term horizon’. Based on the idea that male seek Based on the idea that male seek

immediate gratification- they are not immediate gratification- they are not concerned with long term gains. concerned with long term gains.

In terms of evolution what other In terms of evolution what other reason could there be for risk taking reason could there be for risk taking behaviours if not for sexual selection behaviours if not for sexual selection processes?processes?

Read the text on the Daly & Wilson study Read the text on the Daly & Wilson study and then answer the following questionsand then answer the following questions

1.1. What was the aim of their study?What was the aim of their study?

2.2. How many community areas were involved?How many community areas were involved?

3.3. What is a correlational analysis? What variable did D & W What is a correlational analysis? What variable did D & W correlate in their investigation?correlate in their investigation?

4.4. What was the average life expectancy of the participants? What was the average life expectancy of the participants?

5.5. What did D & W find in relation to life expectancy and What did D & W find in relation to life expectancy and neighbourhood specific homicides? What was the co-neighbourhood specific homicides? What was the co-efficient?efficient?

6.6. They found a negative correlation between life expectancy They found a negative correlation between life expectancy and truancy from school- how was this explained? and truancy from school- how was this explained?

7.7. What problems may arise when using evolutionary What problems may arise when using evolutionary explanations to explain modern day behaviours? explanations to explain modern day behaviours?

8.8. What can we conclude form Daly’s research?What can we conclude form Daly’s research?

9.9. Write 4 evaluation points of the biological explanations-Write 4 evaluation points of the biological explanations-single gene?, environmental influences?, falsifying evolution single gene?, environmental influences?, falsifying evolution explanations?, methods of investigation?, reductionist? explanations?, methods of investigation?, reductionist?

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Biological Explanations of Criminal behaviour