Download Biological theories of offending (slides)

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Today’s session
You are learning about...
You are learning to...
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Interpret, evaluate and
draw conclusions from
evidence
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Biological theories of
offending
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• Later on, I will be giving you a lecture on this.
But first, I want you to use your psychological
skills of interpretation and evaluation to
anticipate what I’m going to tell you.
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Is there a gene for crime?
No. There isn’t.
• ‘Lombrosian’ view:
– Single defective gene responsible
• Modern behavioural genetics:
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– Polygenetic influences
– Complex interactions with environment
– No assumption of defect
Two questions
• Is there a genetic influence on crime?
– Family history studies
– Twin studies
– Adoption studies
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• If so, how does the influence operate?
Family history studies
• Osborne & West (1982)
– Father has a criminal conviction – 40% of sons do
– Father has no criminal conviction – 13% of sons do
• Consistent with genetic influence
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– Also with learning/environment
– Suggests genes do not determine criminality
Twin studies
• Early studies strongly suggested genetic
influence but flaws in sampling, determining
zygocity.
• More recently:
• Low MZ concordances – influence not strong
• Confounding effects of more similar treatment
for MZ
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– Christiansen (1977): MZ 35%; DZ 13%
– Dalgard & Kringlen (1976): MZ 26%; DZ 15%
Adoption studies
• Generally found that adopted children more
similar to biological than adoptive parents.
• Supports genetic hypothesis but:
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– Issue of what is being inherited (e.g. alcoholism)
– Could be prenatal influences, not genetic
– Age at adoption – early influences?
What is being inherited?
• Hollin (1992) gives three suggestions:
• Difficult to resolve because of enormous
complexity of interactions
• Lots of biological correlates of criminality; few
obvious causes.
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– Abnormal CNS e.g. Low IQ; ADHD
– Abnormal ANS e.g. Lack of responsiveness
– Abnormal endocrine e.g. Influence of testosterone
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• Which bits had you already worked out?
• Which bits were new or unexpected given
your own interpretation?