Beware of ceiling effects when testing for moderation: is intergroup contact really more effective for authoritarians?
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). I show that this likely explains the finding by Dhont and Van Dhiel (Dhont and Van Hiel 2009) that intergroup contact is particularly influential for authoritarians, and suggest that this issue might appear more frequently in the intergroup contat literature.
The data: highly skewed
Dhont, Kristof, and Alain Van Hiel. 2009. “We Must Not Be Enemies: Interracial Contact and the Reduction of Prejudice Among Authoritarians.” Personality and Individual Differences 46 (2): 172–77. https://doi.org/10.1016/j.paid.2008.09.022.
Kauff, Mathias, Katharina Schmid, Simon Lolliot, Ananthi Al Ramiah, and Miles Hewstone. 2016. “Intergroup Contact Effects via Ingroup Distancing Among Majority and Minority Groups: Moderation by Social Dominance Orientation.” PLOS ONE 11 (1): e0146895. https://doi.org/10.1371/journal.pone.0146895.
Rohrer, Julia M., and Ruben C. Arslan. 2021. “Precise Answers to Vague Questions: Issues with Interactions.” Advances in Methods and Practices in Psychological Science 4 (2): 25152459211007368. https://doi.org/10.1177/25152459211007368.
Visintin, Emilio Paolo, Jacques Berent, Eva G. T. Green, and Juan Manuel Falomir-Pichastor. 2019. “The Interplay Between Social Dominance Orientation and Intergroup Contact in Explaining Support for Multiculturalism.” Journal of Applied Social Psychology 49 (5): 319–27. https://doi.org/10.1111/jasp.12587.