Like our study, a previous genome-wide association study of digit symbol and symbol search did not uncover any genome-wide significant associations (Cirulli et al., 2010). This study was less powered than ours with a sample size of 1086 and 414 for the respective measures; none of their 100 top SNPs for each analysis overlapped with our top 100. However, for digit symbol eight of their top 100 SNPs (rs9302365, rs2280645, rs10500956, rs1874989, rs17572757, rs4880535, rs9310772, rs9883639) were significant at a nominal level from 89 that we had results for; two of these SNPs were in the ADARB2 gene. For symbol search, three of their top 100 SNPs from 92 that we had results for were nominally significant, these included: rs11812109, rs16896091, and rs4723454. Our study agrees with theirs in that common genes do not influence psychometric speed measures with large effect size.
