The Fallacy of Estimating "Heritability" in Medicine and the Behavioral Sciences
By Jay Joseph. Psy.D (Adapted from a 3/13/2021 twitter post https://twitter.com/jayjoseph22/status/1370785425955065860 ) 1/ Critics argue that “heritability” is a misunderstood and misused concept, and that “heritability estimates,” which range from 0% to 100% (0.0 to 1.0), do not tell us “how much” genes contribute to human behavioral differences, or how “fixed” human behavior is. 2/ Using the example of the disease favism (Glucose-6-phosphate dehydrogenase deficiency), I illustrate the fallacy of using heritability estimates to assess “how much” genes influence behavior (“IQ,” “personality,” psychiatric conditions, and so on). 3/ Favism is caused by an inherited deficiency of glucose-6-phosphate. The predisposing gene is located on the X chromosome. When the carrier eats fava (broad) beans or inhales fava bean pollen, favism appears. The disease is marked by the development of hemolytic anemia. 4/ In other words, “beans and genes” are both necessary for favis...