Moment expressions for individual factor scores can serve as simple tests for the presence of a particular class of interaction factors that are disguised as pure genetic and/or environmental factors. That is, individual genetic and environmental factor scores may be used to construct fourth‐order moments of these factors in order to test whether a common genetic or environmental factor in the multivariate genetic factor model is in fact of the interactive origin concerned. Expected fourth‐order moments are derived for cases with and without interaction. Application of fourth‐order moments of factor scores to detect interactive origin of common factors is illustrated with simulated twin data.
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