Caplan on Genetic Studies Applied to Grit

I’ve recently been talking about grit. Industrial psychology has some literature deflating grit which I criticized. That is, I have been defending grit.

One criticism I gave was that I think some of the genetic claims are incorrect. Bryan Caplan discussed genetic studies at a recent lecture unrelated to grit. His lecture was on Genes and Political Behavior.

Based on his comments, I think my claims about research contra grit deserves further consideration:

  1. Adoption studies and twin studies are two useful ways to analyze nature vs nurture effects.
  2. Adoption studies are able to vary environment, but they can’t hold genetics constant.
  3. Twin studies can’t vary the environment, but they allow genetics to vary in a limited way.
    1. I asked whether non-variation in the X chromosome could lead to systematic bias and his answer was that, “the research shows that dominance sometimes alters key results and sometimes doesn’t matter.”
    2. I believe his comment indicates that there there may be systematic error.
  4. I have previously argued, I also think that unobserved environmental homogeneity in twin studies is often incorrectly identified as genetic similarity.
  5. It seems that adoptive twin studies are the unicorns of genetic research. Because they are both theoretically perfect and non-existant. These studies would allow for better separation of environmental effects and analysis of interactions between genetics and the environment.
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