Would you mind giving a source as well? I've been doing some googling and every paper that references this seems to describe correlations to IQ scores rather t

Would you mind giving a source as well? I've been doing some googling and every paper that references this seems to describe correlations to IQ scores rather than variance of IQ scores. For example Bouchard & McGue (1981) reported a correlation of twin's IQ of 0.86 if living together and 0.71 if living apart. That particular paper doesn't fill me with confidence (it seems to have a sample size of 111 and it's a meta-study), but it appears to be the most cited paper I've seen. I haven't seen anything that discusses a variance of IQ score, nor do I really understand what that means (what's the standard deviation of correlated multivariate distributions?) It would be interesting to see the analysis.