{"id":202,"date":"2023-02-17T22:37:20","date_gmt":"2023-02-17T22:37:20","guid":{"rendered":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/chapter\/3-5-4-heritability-and-genetics\/"},"modified":"2023-06-28T14:00:31","modified_gmt":"2023-06-28T14:00:31","slug":"3-5-4-heritability-and-genetics","status":"publish","type":"chapter","link":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/chapter\/3-5-4-heritability-and-genetics\/","title":{"raw":"Behavior and Genetics: Learn It 4\u2014Heritability and Genetics","rendered":"Behavior and Genetics: Learn It 4\u2014Heritability and Genetics"},"content":{"raw":"

Heritability<\/h2>\r\n
H<\/strong>eritability<\/strong> describes the\u00a0<\/span>proportion of difference among people that is attributed to genetics.<\/span><\/section>
\r\n

heritability coefficient<\/h3>\r\nQ<\/span>uantitative genetics produces a number called a heritability coefficient<\/strong> that is meant to provide a single measure of genetics\u2019 influence on a trait (the number is between 0 to 1, with 1 being the strongest genetic influence). In a general way, a heritability coefficient measures how strongly differences among individuals are related to differences among their genes. For example, let's say the heritability coefficient for height is 0.8. This means that 80% of the variation in height within a population can be explained by genetics, while the other 20% is due to environmental factors like nutrition and lifestyle.\r\n\r\n<\/section>In research compiled from studies of identical twins (in the Minnesota Study of Twins Reared Apart) researchers found that identical twins raised apart exhibit a higher correlation between their IQ scores than siblings or fraternal twins raised together (Bouchard, Lykken, McGue, Segal, & Tellegen, 1990).<\/span>\r\n\r\n<\/section>
\r\n
\r\n
\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"618\"]\"A Figure 1<\/strong>. The correlations of IQs of unrelated versus related persons reared apart or together suggest a genetic component to intelligence.[\/caption]<\/figure>\r\n<\/div>\r\n<\/section>Intelligence in the normal range is a polygenic trait, meaning that it is influenced by more than one gene, and in the case of intelligence at least 500 genes. Further, explaining the similarity in IQ of closely related persons requires careful study because environmental factors may be correlated with genetic factors. Twin studies of adult individuals have found a heritability of IQ between 57% and 73%, with some recent studies showing heritability for IQ as high as 80%.\u00a0Some of the traits that the twin study also reported as having more than 50%\u00a0<\/span>heritability<\/span> ratio include leadership, obedience to authority, a sense of well-being, alienation, resistance to stress, and fearfulness.\u00a0<\/span>It's important to understand that heritability doesn't mean that a trait is completely determined by genes. Instead, it tells us how much of the differences in a trait within a population can be explained by genetics. So, heritability helps us understand the role of genes in shaping our traits, but it's not the whole story.\r\n
\r\n

Genetics and Schizophrenia<\/h2>\r\nThe heritability of schizophrenia is said to be around 79%. This does NOT mean that a person with a parent with schizophrenia has a 79% chance of having schizophrenia, but rather that the 79% of the variation among people who either have or don't have schizophrenia can be explained by genetics. Let's examine this further and look at some findings on schizophrenia in light of what we know about gene-environment interactions.\r\n\r\nIn a 2004 study by Tienari and colleagues, of people who were given up for adoption, adoptees whose biological mothers had schizophrenia and who had been raised in a challenged family environment were much more likely to develop schizophrenia or another psychotic disorder than were any of the other groups in the study:\r\n