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. Author manuscript; available in PMC: 2020 Jan 1.
Published in final edited form as: Intelligence. 2018 Nov 23;72:20–27. doi: 10.1016/j.intell.2018.11.006

Fig. 1.

Fig. 1.

Modified twin-correlation model. CA1 = twin 1 cognitive ability score, CA2 = twin 2 cognitive ability score; z1 = twin 1 latent CA score, z2 = twin 2 latent CA score; SES family SES, S random effect of latent CA on observed CA in standard deviation units; rMZ/rDZ MZ and DZ twin CA correlations, respectively, moderated by family SES. The 0.5 terms in the exponential expressions for the variance are included because s1 and s2 represent the standard deviations of GA, not the variances.