Biological Bases of Behavior

Biological Bases of Behavior - Biological Bases of Behavior...

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Biological Bases of Behavior: Part 1 - Genetics, hormones, basics of the nervous system Behavioral genetics - Genes : segments of DNA that guide the production of proteins to carry out specific tasks o can be “on” or “off” o thought of as the unit of heredity - Genotype vs. Phenotype o Genotype: actual genetic constitution o Phenotype: observable expression of characteristic, results from genes and environment - Role of Heredity: o Same genotype expressed in different phenotypes o Same phenotype result from different genotypes (tongue-rolling) TT = T, Tt = T, tT = T, tt = t Not so simple… can have the gene for tongue rolling, but also a modifier gene “M” that cancels out the tongue rolling proteins. o Determining role of genetics vs. environment Family studies: Francis Galton (Darwin’s cousin) noted intelligence runs in families. But, families don’t just provide genes; they provide environments as well. - Twin studies: correlation between Monozygotic Twin vs. Dizygotic Twin o MZ > DZ: genetic o MZ = DZ: common environment o MZ < 1: unique environment o Heritable ranges: Physical traits – height, weight Disorders – Schizophrenia, affective disorders (depression) Intelligence Temperament/Shyness Social Attitudes (liberalism) / Reliogosity (environment) / Occupation Type Happiness - Adoption studies: twins raised apart o Gold standard of studying heritable traits – but does it really prove genetic basis? What other explanation exists for similarities in twins raised apart? - Why ranges? o Even highly heritable traits can be strongly influenced by the environment (e.g., genetically tall corn vs. short corn – still affected by field conditions) o Genes can help “create” environment (e.g., temperament, physical attractiveness, choices) o Humans can often choose their own environments o Niches – environments and genetics working in concert to support a trait o Inferential mistakes happen both ways – sometimes environmental effects are actually genetic Testosterone o Endocrine system: releases hormones; sex-linked behavior, social behaviors o Prenatal androgens masculinize brains, estrogens feminize them One crude proxy for prenatal androgens? 2d:4d Digit-ratio
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Except for genitalia, digit-ratio is the only physical trait fixed at birth that is sexually differentiated. Other sexually dimorphic traits, such as height or waist-to-hip ratio, don’t appear until puberty. Masc – smaller ratios; longer ring than index
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Biological Bases of Behavior - Biological Bases of Behavior...

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