| The article's explanation of "heritability" of human behavioral traits is poor. For four years now, I've had regular in-person interaction with a "journal club" of researchers and graduate students who are deeply involved in the Minnesota Twin Study. I'm about to go out the door to an in-person meeting of a local nonprofit board, but let me post some links here (embedded in a FAQ file I keep on my personal computer), and invite you to look them up. (They are all peer-reviewed research links that are free to download, by leading researchers on human behavior genetics.) It is well known, on the one hand, that ALL human behavioral characteristics are heritable. (It is an abuse of language to say "heritable" in this context, but the abuse is conventional and standard in the field.) So we can agree with the professional literature that your tendency to vote for one political party rather than another is heritable. Your attribution of causes for human differences (e.g., human differences in IQ) is also heritable. Your opinion about regulation of the Internet is heritable. Everything about human behavior is heritable, including the tendency to loneliness mentioned in the interesting article submitted here. Eric Turkheimer has recently been president of the Behavior Genetics Association, and he has the very kind habit of posting most of his peer-reviewed journal articles on his faculty website. http://people.virginia.edu/~ent3c/vita1_turkheimer.htm Lars Penke is another, younger researcher who posts most of his publications on his personal website. http://www.larspenke.eu/en/publications/publications.html I have the pleasure of meeting many other researchers in human genetics just about weekly during the school year at the University of Minnesota "journal club" Psychology 8935: Readings in Behavioral Genetics and Individual Differences Psychology. From those sources and other sources, I have learned about current review articles on human behavior genetics that help dispel misconceptions that are even commonplace among medically or scientifically trained persons who aren't keeping up with current research. An interesting review article, Turkheimer, E. (2008, Spring). A better way to use twins for developmental research. LIFE Newsletter, 2, 1-5 http://people.virginia.edu/~ent3c/papers2/Articles%20for%20O... admits the disappointment of behavior genetics researchers. "But back to the question: What does heritability mean? Almost everyone who has ever thought about heritability has reached a commonsense intuition about it: One way or another, heritability has to be some kind of index of how genetic a trait is. That intuition explains why so many thousands of heritability coefficients have been calculated over the years. Once the twin registries have been assembled, it's easy and fun, like having a genoscope you can point at one trait after another to take a reading of how genetic things are. Height? Very genetic. Intelligence? Pretty genetic. Schizophrenia? That looks pretty genetic too. Personality? Yep, that too. And over multiple studies and traits the heritabilities go up and down, providing the basis for nearly infinite Talmudic revisions of the grand theories of the heritability of things, perfect grist for the wheels of social science. "Unfortunately, that fundamental intuition is wrong. Heritability isnӴ an index of how genetic a trait is. A great deal of time has been wasted in the effort of measuring the heritability of traits in the false expectation that somehow the genetic nature of psychological phenomena would be revealed. There are many reasons for making this strong statement, but the most important of them harkens back to the description of heritability as an effect size. An effect size of the R2 family is a standardized estimate of the proportion of the variance in one variable that is reduced when another variable is held constant statistically. In this case it is an estimate of how much the variance of a trait would be reduced if everyone were genetically identical. With a moment's thought you can see that the answer to the question of how much variance would be reduced if everyone was genetically identical depends crucially on how genetically different everyone was in the first place." Johnson, Wendy; Turkheimer, Eric; Gottesman, Irving I.; Bouchard Jr., Thomas (2009). Beyond Heritability: Twin Studies in Behavioral Research. Current Directions in Psychological Science, 18, 4, 217-220 http://people.virginia.edu/~ent3c/papers2/Articles%20for%20O... is another interesting review article that includes the statement "Moreover, even highly heritable traits can be strongly manipulated by the environment, so heritability has little if anything to do with controllability. For example, height is on the order of 90% heritable, yet North and South Koreans, who come from the same genetic background, presently differ in average height by a full 6 inches (Pak, 2004; Schwekendiek, 2008)." The review article "The neuroscience of human intelligence differences" by Deary and Johnson and Penke (2010) relates specifically to human intelligence: http://www.larspenke.eu/pdfs/Deary_Penke_Johnson_2010_-_Neur... "At this point, it seems unlikely that single genetic loci have major effects on normal-range intelligence. For example, a modestly sized genome-wide study of the general intelligence factor derived from ten separate test scores in the cAnTAB cognitive test battery did not find any important genome-wide single nucleotide polymorphisms or copy number variants, and did not replicate genetic variants that had previously been associated with cognitive ability[note 48]." (The same would be expected of characteristics like loneliness.) Johnson, W., Penke, L., & Spinath, F. M. (2011). Understanding Heritability: What it is and What it is Not. European Journal of Personality, 25(4), 287-294. DOI: 10.1002/per.835 http://www.larspenke.eu/pdfs/Johnson_Penke_Spinath_2011_-_He... responds to psychologists' comments about their earlier review article on heritability. "Our target article was intended to provide background knowledge to psychologists and other social scientists on the subject of heritability. This statistic, in many ways so basic, is both extremely powerful in revealing the presence of genetic influence and very weak in providing much information beyond this. Many forms of measurement error, statistical artefact, violation of underlying assumptions, gene–environment interplay, epigenetic mechanisms and no doubt processes we have not yet even identified can contribute to the magnitudes of heritability estimates. If psychologists and other social scientists want to understand genetic involvement in behavioural traits, we believe that it is going to be necessary to distinguish among these possibilities to at least some degree. Heritability estimates alone are not going to help us do this." Turkheimer, E. (2011). Genetics and human agency (Commentary on Dar-Nimrod & Heine, 2011). Psychological Bulletin, 137, 825-828. DOI: 10.1037/a0024306 http://people.virginia.edu/~ent3c/papers2/Articles%20for%20O... reemphasizes the point that a heritability calculation tells us nothing about subject to environmental influences a human trait is. "That heritability depends on the population in which it is measured is one of the most frequently repeated caveats in the social sciences, but it is nevertheless often forgotten in the breach. (For example, it is nearly meaningless for Dar-Nimrod and Heine to note that 'heritability [of intelligence is] typically estimated to range from .50 to .85' [p. 805]. The heritability of intelligence isn’t anything, and even placing it in a range is misleading. Making a numerical point estimate of the heritability of intelligence is akin to saying, 'Social psychologists usually estimate the F ratio for the fundamental attribution error to be between 2.0 and 4.0.') The observation that genotypic variation accounts for 90% of the variation in height in the modern world depends on the variability of genotype and environment relevant to height. Among cloned animals with widely varying diets, body size is perfectly environmental with heritability of 0; in genetically variable animals raised in identical environments heritability is 1.0. This is no mere statistical fine point: it means that the entire project of assessing how essentially genetic traits are in terms of measured heritability coefficients is a fool’s errand." The full text of the articles at the links, which in some cases focus on IQ and in other cases are more general, will give you more background in the methods and reasoning used by researchers on the topic of human behavioral genetics. |