Table 1:

Strengths and limitations of methods for causal inference.

	Ruled out by . . .
	WF	LDSC	LCV
Confounding by shared environment	Yes	Yes	No
Confounding by non-shared environment	No	Yes	No
Cross-assortative mating	Yes	No	No
Genetic pleiotropy	No	No	Yes
Reverse causation	No	No	Yes

Each row corresponds to an alternative explanation of the correlation between brain size and intelligence other than the former being a cause of the latter. “Yes” indicates that a positive result obtained with the method given in the column provides evidence against that alternative explanation. A simple yes- or-no answer is always given for the sake of simplicity; consult the text for more nuance. WF, within-family phenotypic association; LDSC, bivariate LD Score regression; LCV, Latent Causal Variable.