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Today’s session. 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. Is there a gene for crime?. No. There isn’t. ‘Lombrosian’ view:
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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.
No. There isn’t. • ‘Lombrosian’ view: • Single defective gene responsible • Modern behavioural genetics: • 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 • 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 • 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: • Christiansen (1977): MZ 35%; DZ 13% • Dalgard & Kringlen (1976): MZ 26%; DZ 15% • Low MZ concordances – influence not strong • Confounding effects of more similar treatment for MZ
Adoption studies • Generally found that adopted children more similar to biological than adoptive parents. • Supports genetic hypothesis but: • 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: • Abnormal CNS e.g. Low IQ; ADHD • Abnormal ANS e.g. Lack of responsiveness • Abnormal endocrine e.g. Influence of testosterone • Difficult to resolve because of enormous complexity of interactions • Lots of biological correlates of criminality; few obvious causes.
Which bits had you already worked out? • Which bits were new or unexpected given your own interpretation?