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Fortunately, they can be overcome…If the 2 kind of studies produce similar results on the influence of heredity, we can be confident of those results4.Polygenic inheritance has been examined more recently by isolating particular segments of DNA which serves as a marker for identifying specific alleles1.Compare DNA markers between 2 groups that differ in the behavior/psychological trait being studied; if different consistently = alleles near the marker probably contribute to the differences b/w the groups
Genetic Bases of Child DevelopmentChapter 22.Have the potential to identify the many diff. genes that contribute to complex behavioral and psychological traits3.Limits1.Requires large samples2.Some require investigator have an idea before even beginning to study about which chromosomes to search and where5.Which psychological characteristics are affected by heredity?1.Research reveals consistent genetic influence in many psychological areas (personality, mental abilities, psychological disorders, attitudes, and interests2.Study looking at depression: Twin studies MZ twins show remarkable similarity (if 1 twin depressed, other has ~50% chance of being depressed as well); for DZ twin’s percentage is much lower (~25%)3.Can also see the influence of heredity in cognitive development 1.Study looking at heredity and environmental bases of aggressive behaviors between twins 6 years of age (234 pairs of twins)1.Teachers/peers rated each twin on levels of social and physical aggression2.Results for physical aggression: highest correlation b/w MZ twins (twice as highly correlated as same-sex DZ twins) 3.Results for social aggression: roughly equal for all twin pair types 4.Conclusion: Strong genetic component to physical aggression, but a more environmental explanation for social aggression envir./exposure to certain envir. Factors must contribute/influence behavior; physical aggression tended to underlie social aggression5.Converging evidence to strengthen proposed conclusion that aggression and the diff. effects of diff. influences on aggression change over time = Conduct a longitudinal study to see whether MZ and DZ twins’ aggressive behaviors would become more or less alike as they grew1.PATHS FROM GENES TO BHEAVIOUR6.1) The behavioral consequences of genetic instructions depend on the environment in which those instructions develop 1.Reaction rages same genotype can produce a range of phenotypes in reaction to the envir. Where development takes place
Genetic Bases of Child DevelopmentChapter 21.Ex: Child brought up in an impoverished non-stimulating envir. = Phenotypic intelligence may be below avg. compared to an enriched envir. Filled with stimulation = phenotypic intelligence may be above avg.