AC 2.1-Biological

• What’s are the biological/genetic theories of criminality:

  -Jacob’s ”XYY” theory

  -Adoption studies

  -Twin studies
• XYY theory:

  -This theory suggest that males with an extra Y chromosome (47,XYY karyotype) might have a higher tendency toward criminal behavior. This theory was based on early studies that found an increased prevalence of XYY males in prisons and among individuals convicted of violent crimes.

  -they have more testosterone so believed to commit violent and sexual crimes

  -they are big and tall with acne and have learning disabilities
• Strengths of “XYY” theory of criminality:

  -Jacob et al found an association between

  XYY syndrome and offenders punished for violent behaviour.

  -Price and what more found links between XYY and property crime.
• Weaknesses of “XYY” theory of criminality:

  -the syndrome itself is very rare and cannot explain the cause of criminality.

  -People with XXY may experience stereotyping and labelled. They may receive harsher sentences in court.

  -XYY may have low intelligence so therefore they would be more likely to be caught which disproves the theory.
• Twin studies:

  -identical twin (monozygotic) are more likely to be criminals.

  -twin pairs show similar behaviours so if one is a criminal so will the other one.
• Strengths of Twin studies theory of criminality:

  -christiansen study on 3500 twins found 52% concordance in monozygotic twins.

  -Monozygotic twins are genetically identical so we can examine if there offending is identical
• Weaknesses of Twin studies theory of criminality:

  -Higher rates of concordance may be because they share a home. Shared environments can cause similar behaviour rather than genes.

  -Parents treat MZ twins more identically than DZ twins and are therefore influence each other to become criminal.

  -sampling bias along with ethical concerns