My views have evolved since the unfinished series of posts (1, 2, 3, 4) that considered the connection between two different Nature-Nurture issues: the matter of fixity versus flexibility in the development of traits in individuals over their life course and the relative degrees of hereditary versus environmental influences on the variation of the trait between versus within groups. I now see that there are five (if not more) forms of Nature-Nurture science. This post is a placeholder for more extended discussion of how, in the long history of nature-nurture debates, opposing sides often assume, imply, or propose that these different sciences are speaking to the same issues.
- Researchers can try to compare how much variation is associated with differences among means for varieties, locations, variety-location combinations, and residual contributions (i.e., genotypic, environmental, genotype-environment interaction, and residual variance).
- Researchers can try to compare how much variation is associated with differences in measured genetic factors, environmental factors, gene-environment interaction, and a residual component.
- Through either of the above forms of analysis, researchers can compare the variation within groups (e.g., among Euro-Americans and among African-Americans) to the difference between the averages for the groups.
- Through investigations that might extend any of the preceding kinds of analysis of observational data, researchers can piece together a picture of the processes of development of a trait and, on that basis, speak to the fixity versus flexibility of traits.
- Researchers can provide an evolutionary account of the increase in frequency of a trait through natural selection based on the trait’s superior function in the environment.
To be elaborated on in due course.