One-Mediator Model of Exposure Effects Is Still Viable

Birnbaum and Mellers criticized the use of partial correlation and multiple regression by Moreland and Zajonc to argue for two independent effects of stimulus exposure on liking. The null hypothesis that one variable mediates the effect of the independent variable on the dependent variables was not tested by their analyses. In response, Moreland and Zajonc reanalyzed their data, using structural equations analysis, and replied that there is evidence to support their previous conclusions. However, the present article shows that the small residuals from the one-mediator model may be due to shared nonlinearity (correlated errors) in three of the dependent variables. This simpler interpretation achieves a better fit to the Moreland and Zajonc data than the two-mediator model they advocated. Since the null hypothesis of one mediator is still viable, the burden of proof rests on those who contend that there is more to the exposure effect than stimulus recognition.