Beware of ceiling effects when testing for moderation: is intergroup contact really more effective for authoritarians?

TL;DR Moderation tests identify whether the link between a predictor and an outcome depends on the level of another variable. Spurious results are likely to appear when a) the predictor is influenced by floor or ceiling effects and b) predictor and moderator are correlated (recently pointed out by Rohrer and Arslan 2021, Box 1).