EDUC 391 Intelligence in Everyday Life


P/F Writing Assignment for Day 20

Genetics of Intelligence II: Two big surprises


In pp. 29-35, Eysenck argues against extreme environmentalism by listing various sorts of evidence for the heritability of IQ. We covered some of that evidence during the last class. His more important points come later. Let's focus on them. For instance,

1. Eysenck reviews two fairly recent findings findings that shocked even behavioral geneticists: (a) the heritability of IQ rises with age and (b) shared family effects on IQ essentially disappear by adolescence. (NOTE: The Plomin & Petrill article from Day 18, pages 59-66, has clear description of these two surprises. It may help to skim this to get a clearer idea of what Eysenck is describing.) Eysenck uses a single theory--often called "niche seeking"--to explain both these effects. Describe that theory and how it explains both effects.

  • Please describe an instance of such niche seeking that you have observed in either yourself or others.

2. If the differences among us in some trait (e.g., intelligence, extraversion) are highly heritable, does that mean that a person's intelligence is "fixed" or "immutable" or unchangeable--that mental ability does not and cannot change over a life time? Please explain. Your answer should reflect an understanding of what “heritability” means.

3. Some people mistakenly think that if IQ is highly genetic, then parents and their children, or siblings, must be like peas in a pod (have the same intelligence, personality, occupational success, etc.). We might call this the genetic caste theory of life. In the very same fashion, some people mistakenly think that people who grow up in the same family will be like peas in a pod (this time for environmental reasons). We might call this the environmental caste theory of life. Please give evidence from all three readings for why both these theories are false:

  • Eysenck reading, especially pages 36 (very bottom) to 40
  • Deary's Dataset 8
  • short Murray article.

P.S.: If you don't know what "nihilism" means, look it up.