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:
- Adoption studies and twin studies are two useful ways to analyze nature vs nurture effects.
- Adoption studies are able to vary environment, but they can’t hold genetics constant.
- Twin studies can’t vary the environment, but they allow genetics to vary in a limited way.
- 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.”
- I believe his comment indicates that there there may be systematic error.
- I have previously argued, I also think that unobserved environmental homogeneity in twin studies is often incorrectly identified as genetic similarity.
- 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.