Biological theories of criminality: genetic theories Flashcards
What is the genetic explanation?
Criminality is the result of genes inherited from biological parents
What is monozygotic?
Identical twins that share 100% of the same genes
What is dizygotic?
Non-identical twins that share only 50% of the same genes (like ordinary siblings)
What is the environmental explanation?
Criminality is the result of the surroundings a child grows up in
What is a chromosome?
Made from DNA and protein. Carry genetic information we inherit from our parents. Most people have 23 pairs
What is a super male?
Another term for XYY syndrome. Those affected carry an extra Y (male) chromosome on one of their 23 pairs
What were the key ideas of the twin in twin and adoption studies?
If crime is genetic – identical (Mz) twins should have identical criminality
What were the findings of the twin in twin and adoption studies?
Christiansen: Concordance in criminality Mz = 52% vs Dz = 22%
What were the key ideas of the adoption in twin and adoption studies?
Adoptees share environment of adoptive parents/genes of biological parents. If genetic, criminality will match biological parents more
What were the findings of the adoption in twin and adoption studies?
Mednick et al: birth parent concordance = 20% vs. adopted parent concordance = 14.7%
What is one strength of the twin and adoption studies?
Twin & adoption studies give some support to genetic explanations
What is a second strength of the twin and adoption studies?
Adoption studies overcome the problem of isolating genes and environment
What is a third strength of the twin and adoption studies?
Research design of Adoption studies is logical (nature vs nurture)
What is one limitation of the twin and adoption studies?
If criminality was only genetic MZ twins would have 100% concordance
What is a second limitation of the twin and adoption studies?
It is impossible to isolate genetic effects fully from environmental ones
What is a third limitation of the twin and adoption studies?
Adopted children are often placed with similar families to their birth family
What were the key ideas of Jacob’s XYY study?
XYY syndrome in males makes them genetically predisposed to criminality
What was the study of Jacob’s XYY study?
Compared rate of XXY in imprisoned criminals with general population
What were the findings of Jacob’s XYY study?
Higher than average proportion of inmates had XYY
What were the features of XYY?
Very tall, well-built, low intelligence, high aggression, violent
What is one strength of Jacob’s XYY study?
acob et al found association with XXY and violent prisoners
What is a second strength of Jacob’s XYY study?
Price & Watmore found links with XYY and property crime
What is one limitation of Jacob’s XYY study?
Having the syndrome doesn’t mean that is the cause of crime
What is a second limitation of Jacob’s XYY study?
XXY men fit stereotype of violent offenders – labelling theory
What is a third limitation of Jacob’s XYY study?
Low intelligence of XYY may give higher chance of being caught
What is a fourth limitation of Jacob’s XYY study?
Syndrome is too rare to explain much crime
