The Bell-Curve Fallacy and Other Misinterpretations of Heritability
• Formula of heritability includes both genetic variation, V and environmental variation, V .
• Any estimate is specific to particular population living in particular environment.
• Heritability tells us nothing about causes of differences between populations that live in diff.
• Jens Clausen, David Keck, and William Hiesey studied Achillea, a perennial wildflower. Achillea grew
from cuttings, making it possible to created clones of single individual. Researchers collected seven
plants from wild population and took two cuttings from each.
• Researcher grew one cutting from each plant in experimental garden in Mather, California. As the
cuttings grew up side by side, they experienced virtually the same environmental, differences among
them in height at maturation almost entirely due to genetic variation.
• Researchers grew second cutting from each plant in experimental garden at Standford, California. The
plants experienced virtually same environment, differences among them in height at maturation are
entirely due to genetic variation.
• Plants in Standford population on average taller than plants in Mather population. The fact that
heritability is high in each population tells us nothing about cause of differences between populations,
because populations reared in diff. environments.
• Mistaken notion that heritability tells us something about causes of diff. between populations has been
persistent in studies of human intelligence.
• Murray and Herrnstein claimed that difference in average IQ scores between African Americans and
European Americans is due to genetic differences between these groups. They understood that I.Q. is
substantially heritable yet does not tell us anything about origin of difference between groups.
• Murray and Herrnstein proceeded to develop erroneous arguments.
• They imagined tha