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Chuck's avatar

To note, the concepts of biometric gene × environment interaction (G×E) and heritability × environment interactions are frequently conflated in the literature but represent distinct phenomena. G×E, a term in standard biometric models, quantifies the proportion of phenotypic variance due to interactions between genotypes and environments, where specific genotypes exhibit differential responses to environmental conditions. For example, one plant variety may thrive in fertile soil but perform poorly in arid conditions, while another shows the reverse pattern, with this variance attributed to G×E. Conversely, heritability × environment interactions describe how the proportion of phenotypic variance explained by genetic factors (heritability, h²) varies across environments, typically due to changes in total phenotypic variance. For instance, human height may have high heritability (h² = 0.8) in a stable environment, but in a malnutrition-prevalent environment, increased environmental variance may reduce heritability (e.g., h² = 0.5), even if genetic variance remains unchanged. In essence, G×E captures genotype-environment synergies, whereas heritability × environment interactions reflect shifts in the relative genetic contribution to phenotypic variance.

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Ruben C. Arslan's avatar

Nice follow up. I often make the same point. A note: I wouldn’t be too quick to dismiss that the Flynn effect taps a real increase. Sure, measurement is a bigger concern than for height. But surely, the fact that we have good evidence that some of the causal antecedents changed over time (nutrient deficiencies, general health, and education) as well counts for something. I think it can be squared with the problem that it cannot be true that people a hundred years ago were disabled if you consider specialization. We probably lost something on a few specific skills around navigation, knowledge of plants and crafts (not tapped well in standard tests) and gained in academics.

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