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Tucker-Drob and colleagues demonstrated that general intelligence (g) has a genetic basis, showing that it is not merely a statistical artifact. Their findings are detailed in the study titled "Genetic 'General Intelligence,' Objectively Determined and Measured," - https://www.biorxiv.org/content/10.1101/766600v3.full

James Lee (behavioral geneticist):

Roderick McDonald criticized the naming fallacy. Just saying that all correlated scores on a test are caused by a common factor is circular reasoning.

Instead, it is a much more important scientific discovery to identify an outside variable that causes observed scores to correlate.

An alternative to the factor model is the network model. It claims that there is no "mental property" that can be affected in a manner propagated to all of its observable indicators. These connections or "bonds" were hypothetical in the early 20th century. Today, they could be considered being genes that are inherited together, or brain regions that are connected.

In the factor model, if a SNP has a causal impact on a trait, then its relationship with observed scores are in proportional to the effect of the SNP, multiplied by the factor loading.

In contrast, network models make no prediction like that. There is no particular expected relationship among SNP effect, observed scores, and factor loadings.

We re-analyzed GWAS data to test these competing theories. "We found a very large number of SNPs whose pattern of associations with items matched the factor models. . . . We had a lot of SNPs that had effects that were almost exactly as predicted."

(Everything Lee is saying is in relation to personality traits, especially neuroticism.)

It is reasonable to expect these results to apply to intelligence because factor models tend to fit better with intelligence data than personality data. A study from de la Fuente et al. (2021) indicates that this may be so, but there is caution because there may be some ascertainment bias in that study.

So, what kind of thing is a psychological trait? The question remains open. But the common factors of factor analysis are real things that are subjected to physical causes of genetics and the brain

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