Biological Theories

• Sheldon examined 4,000 scantily clad photographs of the male body and developed somatotypes that can be linked to criminal behaviour.
• What are the three somatotypes:

  Endomorphs, ectomorphs and mesomorphs
• Endomorphs are round, soft and fat. They also lack in muscle and have wide hips.
• Endomorphs have a sociable, relaxed and outgoing personality.
• Endomorphs are the least likely to commit crimes but the most likely to have a mental illness.
• Mesomorphs are muscular with very little fat and strong limbs, broad shoulders and a narrow waist.
• Mesomorphs have an adventurous and assertive personality. They also enjoy physical activity.
• Mesomorphs are the most likely to commit violent and aggressive crimes.
• Ectomorphs are thin and fragile and lack in fat and muscle.
• Ectomorphs personality is conscious fragile and thoughtful
• Ectomorphs are the least likely to be criminals but are the most likely to commit suicide
• Sheldon used 2 samples of photographs - for college students and delinquents. He then rated them on a scale from 1-7 based on how mesomorph they were.
• Delinquents (4.6) and College students (3.8)
• Strength of somatotypes

  Used a sample size of 200 and used a control group of non-offenders which increase the validity
• Strength of somatotypes

  Glueck and Glueck (1956) found that 60% of delinquents were mesomorphs while only 31% of non delinquents were.
• Strengths of somatotypes

  Putwain and Sammons (2002) found an association between bodybuilding and criminality
• Weaknesses of Sheldon

  Didn't explain how ectomorphs and endomorphs can become criminals
• Weaknesses of Sheldon

  Theory doesn't take into account that an individuals somatotype is not fixed and can change.
• Weaknesses of Sheldon

  Labelling could be a problem because mesomorphs would be more likely to be seen as criminals.
• If crime is 'inborn' it could be presumed that it is passed on from parent to child through DNA.
• It is likely that if a blood relative has a criminal gene then the child will have a higher chance of becoming criminals.
• Evidence for twin studies:

  Lange (1929) found that monozygotic twins had a higher degree of concordance than dizygotic twins. 10/13 monozygotic twins had served time in prison whereas 2/17 dizygotic twins had served time in prison.
• Evidence for twin studies

  Christiansen (1977) studied 3,586 from Danish islands where at least one had a conviction.
• Christiansen findings (male)

  Found concordance rates of 35% for monozygotic and 21% for dizygotic in male twins
• Christiansen findings (female)

  Found concordance rates of 21% for monozygotic and 8% for dizygotic in female twins
• Ishikawa and Raine (2002) 


  Examined twins with convictions
• Ishikawa and Raine findings

  Found 44% concordance rates for monozygotic twins and found 21.6% concordance rates for dizygotic twins.
• Strength of twin studies

  These studies don't involve any manipulation of variables as the biological relationships between twins is naturally occurring which adds validity.
• Strength of twin studies

  Christiansen (1977) supports the view that criminality has a genetic component.
• Strength of twin studies

  The result of twin studies have helped to prevent vulnerable disorders which have high concordance rates.
• Weakness of twin studies

  Some of the first twin studies lacked validity and were not adequately controlled e.g. Lange didn't distinguish between monozygotic and dizygotic twins.
• Weakness of twin studies

  Small samples are used, which aren't representative of the whole population
• Weakness of twin studies

  If twins are brought up in the same environment, then criminality can be linked to environmental factors rather than genetic.
• Biochemical substances and processes affect brain chemistry and mental processes.
• Hormones

  Low levels of serotonin can be linked to high levels of aggression. Serotonin regulates the signals between neurons and a person's mood.
• Scerbo and Raine (1993)

  Found low levels of serotonin in anti-social children and adults when conducting a meta-analysis of 29 studies
• Testosterone is linked with aggression
• Ellis and Coontz (1990)

  Found that testosterone levels peak from puberty to the early 20s and this age range correlates with the highest crime rates in males.
• Pre-menstrual tension, post natal depression and lactation have all been accepted as partial defences for women charged with crimes because hormones have affected the women's judgement, mood or self control.
• Hypoglycemia can trigger aggressive reactions. Low blood sugar can be linked to alcohol abuse