Jacob's XYY study

Question 1

What is it?

Answer 1

Abnormality of the sex chromosomes and another possible
genetic cause of criminality.

Question 2

Appearance

Answer 2

tend to be
tall, very well built
and lacking in
intelligence.

Question 3

How did Jacob link w/ criminality

Answer 3

Claims with XYY are more aggressive than XY men.

Question 4

Evidence

Answer 4

XYY men are over-represented in the prison population.
15 per 1000 in the prison population.
1 per 1000 in the general population.

Had history of aggression and violent assaults.

Question 5

Strengths

Answer 5

Jacob et al found association between XYY syndrome and offenders imprisoned for violence.
Price and Whatmore find some links between the syndrome and property crime

Question 6

Weaknesses

Answer 6

Syndrome is very rare, so it cannot explain much crime.
Even if some violent offenders have the syndrome, this doesn’t prove it is the cause of their violence