In Add Health, where our measure of cognitive performance is the respondent’s score on a test of verbal cognition, the incremental R2s of the GWAS and MTAG scores are 5.1% and 6.9%, respectively. To obtain a better measure prediction accuracy for cognitive performance, we used an additional validation cohort, the Wisconsin Longitudinal Study (WLS), which administered a cognitive test with excellent retest reliability and psychometric properties similar to those used in our discovery GWAS of cognitive performance. In the WLS, the MTAG score predicts 9.7% of the variance in Cognitive Performance, a substantial improvement over the 7.0% predicted by the GWAS score and approximately double the prediction accuracy reported in three recent GWASs of cognitive performance29–31.
