Unit 2.1- biological theories

What do biological theories focus on?

The idea that physical characteristics can make people more likely to commit crime. Some criminal tendencies can be genetic and so inherited

Genetic theories

Criminality running in your genes

physiological theories

Is someone criminal just because from their physical appearance

Johannes Lange (1929)

Studied 13 mz and 17 dz twins

Found 10/13 mz twins had both served time in prison

2/17 dz twins had both served time in prison

Christiansen (1977)

Studies offending behaviour of 3,586 twins pairs born in Denmark between 1881 and 1910

Male concordance rate for Christiansen

Mz-35%

Dz-13%

Female concordance rate for Christiansen

Mz-21%

Dz-8%

How do findings not indicate inheritance for twin studies

Concordance rates are low even for mz twins showing environment plays vital role in behaviour

Difference between male and female twins pairs show a role of gender in criminal behaviour

Problems with twin studies

Must remember the effects of shared effects of shared upbringing

If criminal behaviour was really genetic then the concordance rates would be 100% for mz twins

Concordance rates

The probability that if one twin has a characteristic the other twin will have that characteristic

Monozygotic twins

Come from one egg and share 100% of their DNA

Dizygotic twins

Come from two separate eggs and share 50% of their DNA

Chromosomes

Strands of condensed DNA, where you find individual genes for every physical characterisitcs

Genes

Units of DNA which code for a characteristic and are inherited

Adoption studies

Adopted children are compared to their biological and adopted parents to see which has more influence-biology or environment

How many sons did Mednick study

Over 14,000 adopted sons in Denmark

Concordance rates with birth parents for Mednick

20% concordance rates if a birth parent also had a record

Concordance rates with adoptive parents for Mednick

14.7% concordance rates if the adoptive parents had a criminal records

Conclusion of Mednick study

Adoptees with criminal records were more likely to have biological parents with criminal records.

XYY condition

A condition where people can be born with additional chromosomes

what are XYY men also known as

Super males, they are more aggressive and violent than males with only a single Y chromosome

Jacobs XYY study conclusion

15 in 1000 men in prisons had XYY

1 in 1000 men in the general population XYY

Jacobs XYY case study

John Wayne Gacy- thought it have this syndrome, sexually assaulted, tortured and murdered at least 33 boys in the US

What did Lombroso say that criminals were

‘genetic throwbacks’-a primitive subspecies different to non-criminals

How where offenders seen by Lombroso

As lacking in evolutionary development so impossible to adjust to civilised society so eventually turn to crime

What did Lombroso’s Atavistic form examine

The facial and cranial features of Italian convicts, found 40% of criminal acts could be accounted for by atavistic characteristics

Examples of atavistic charactericitics

Swollen fleshy lips and protruding ears (sexual sadist)

Thin lips (murders)

Exceptionally long arms

what were Sheldon’s somatotypes

Ectomorphic

Mesomorphic

Endomorphic

Ectomorphic

Thin and fragile means they are shy and introverted

Mesomorphic

Muscular so tend to be aggressive and adventurous

Endomorphic

Fat and soft so social and relaxed

Sheldon somatotypes findings

Found many criminals prone to committing violent and aggressive were mesomorphic and least likely were ectomorphic

amygdala

Responsible for regulating the emotions, an abnormality in the area mean emotions aren't regulated so more aggressive

Physiological theories

Sheldon Somatotypes

Lombroso's atavistic form

Neurochemicals

Steroids

Brain abnormalities

Genetic theories

Twin studies

Adoption studies

Jacobs XYY

Neurochemical cause for criminality

Serotonin is associated with regulating mood and behaviour, Scerbo and Raine found after a meta analysis of 29 studies into antisocial behaviour, a majority had low levels of serotonin

Steroids affect on criminality

An increase in testosterone increases aggression, an American bodybuilder beat a man to death after taking 2000 times the recommended amount

Brain abnormality-Raine et al

Found reduced activity in offenders in areas like corpus collosum and prefrontal cortex as well as limbic system which are the emotion centres.

Brain abnormality- case study

Charles Whitman killed 17 people in total, had a tumour pressing on his amygdala resulting in aggression

Phineas Gage- iron rod penetrated his frontal lobes, survived but became more aggressive and wasn't allowed near women or children, first evidence that the frontal lobes accounted for personality.