Different measures of intelligence were assessed in each cohort but were all operationalized to index a common latent g factor underlying multiple dimensions of cognitive functioning. With the exception of HiQ/HRS, all cohorts extracted a single sum score, mean score, or factor score from a multidimensional set of cognitive performance tests and used this normally-distributed score as the phenotype in a covariate-adjusted (e.g. age, sex, ancestry principal components) GWAS using linear regression methods. For HiQ/HRS, a logistic regression GWAS was run with “case” status reflecting whether participants were drawn from an extreme-sampled population of very high intelligence (i.e. at the upper ~0.03% of the tail of the normal distribution) versus an epidemiological sample of unselected population “controls”. Detailed descriptions of the samples, measures, genotyping, quality control, and analysis procedures for each cohort are provided in the Supplementary Note (Supplementary Information 1.1–1.2), Supplementary Table 1, and in the Life Sciences Reporting Summary.
