Instinct, Learning and Motivation: How do Genes Influence Behaviour PDF

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Instinct, Learning and Motivation lecture about how genes influence behaviour....

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PSY1006: How do genes influence behaviour? Westermarck (1891): sexual disinterest/aversion in other children one is raised with = sexual negative imprinting. Co-residence is necessary for negative sexual imprinting.

From gene to behaviour Kallman syndrome o

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1856 post-mortem of a 40-year-old man: - No sense of smell - No olfactory bulbs in brain - Small genitals - No libido One gene identified: KAL-1 found on the X chromosome.

Behaviour to genes o o o o o o

Behavioural libido reduced. Low testosterone. Reduced gonadotropins, LH and FSH. GnRH is absent and not entering the pituitary glands. No GnRH cells in the brain. No protein produced by gene Xp – 22.3.

Bobrow, Money and Lewis 1971 -

Five patients with Kallman’s syndrome. Social development and participation were delayed. Dating behaviour was limited before and after treatment. Sexual interest was low even for those married. Experience of falling in love was absent in relationships. None of the patients had any problems with gender identity.

Beyond instinct: the role of genotype and experience in behavioural development Two questions about the roles of genotype and experience must not be confused: 1) Accounting for differences in behaviour between individuals. 2) Explaining the development of behaviour in the individual.

Accounting for differences in behaviour between individuals What effect does a difference between 2 individuals in their genotype or environment have on the difference in their behaviour? o o

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Genetic influence varies with the environment and environmental influence varies with the genotype. Bovet et al (1969) taught mice to avoid a stimulus and found that mice with the C3H/He gene performed well after a 24 hour gap between each session of learning. Mice with the DBA/2J gene performed worse with a 24 hour gap, suggesting their genes impact how they learn and remember.

Heritability o o

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Heritability (h) is the proportion of variation due to genetic variation between individuals. An example is height: - If people differed in height due to differences only in their genotype, then h = 1. - If people differed in height due to differences only in their environment, then h = 0. E.g. IQ: 30 twin studies, 10,000 pairs of MZ and DZ twins. Mean heritability of IQ = 0.5. Range was 0.3-0.7. Heritability isn’t fixed: heritability increases with socioeconomic status (SES). Impoverished families: 60% of variance in IQ is accounted for by the environment. IQ is more explained by environment in those with a low SES (Turkheimer et al 2003).

Heritability isn’t the same as genetic influence o o o o o o

E.g. trait of walking on two legs. Variance in leg number is mostly due to environment: like accidents, diseases and toxins before birth. Variation due to genetic defects is very rare. 100% genotype, h = 1. 100% environment, h = 0. Heritability of leg number is close to 0....