true correlation of 0.1 will be attenuated to a correlation of 0.06 (60%). Therefore, when the analysis on 5 items is based on the sum score, and the true MZ correlation equals twice the DZ correlation, this ratio is maintained when analysing sum scores. Thus, when applying an AE model, heritability will be underestimated, but no artifactual shared environmental effects or dominance genetic effects will appear as a result of analysing sum scores.
