最近，做中介效应，也是一边用一边巩固，结果出了一个遮掩效应，中文随意翻，没看太明白。找了一篇英文讲得清楚，在此，分享。Prev Sci. 2000 Dec; 1(4): 173.
Equivalence of the Mediation, Confounding and Suppression Effect
David P. MacKinnon,1,2 Jennifer L. Krull,1 and Chondra M. Lockwood1

该文介绍了中介、混淆和遮掩效应，并进行了比较，在此，仅粘贴遮掩效应。

  SUPPRESSION
In confounding and mediational hypotheses, it is typically assumed that statistical adjustment for a third variable will reduce the magnitude of the relationship between the independent and dependent variables. In the mediational context, the relationship is reduced because the mediator explains part or all of the relationship because it is in the causal path between the independent and dependent variables. In confounding, the relationship is reduced because the third variable removes distortion due to the confounding variable. However, it is possible that the statistical removal of a mediational or confounding effect could increase the magnitude of the relationship between the independent and dependent variable. Such a change would indicate suppression.

Suppression is a concept most often discussed in the context of educational and psychological testing (Cohen & Cohen, 1983; Horst, 1941; Lord & Novick, 1968; Velicer, 1978). Conger (1974, pp. 36–37) provides the most generally accepted definition of a suppressor variable (Tzelgov & Henik, 1991): “a variable which increases the predictive validity of another variable (or set of variables) by its inclusion in a regression equation,” where predictive validity is assessed by the magnitude of the regression coefficient. Thus, a situation in which the magnitude of the relationship between an independent variable and a dependent variable becomes larger when a third variable is included would indicate suppression. We focus on the Conger definition of suppression in this article, although there are more detailed discussions of suppression based on the correlations among variables (see above references and also Hamilton, 1987; Sharpe & Roberts, 1997).