Faulty assumptions: A comment on Blanton, Jaccard, Gonzales, and Christie (2006)

Blanton, Jaccard, Gonzales, and Christie [Blanton, H., Jaccard, J., Gonzales, P., Christie, C. (2006). Decoding the Implicit Association Test: implications for criterion prediction. Journal of Experimental Social Psychology, 42, 192–212.] assert that the Implicit Association Test (IAT) imposes a model that portrays relative preferences as the additive difference between single attitudes. This assertion is misplaced because relative preferences do not necessarily reduce to component attitudes. BJGC also assume that the IAT conditions represent two indicators of the same construct. This assumption is incorrect, and is the cause of their poor-fitting models. The IAT, like other experimental paradigms, contrasts performance between interdependent conditions, and cannot be reduced to component parts. This is true whether calculating a simple difference between conditions, or using the IAT D score. D—an individual effect size that is monotonically related to Cohen’s d—codifies the interdependency between IAT conditions. When their unjustified psychometric assumptions are replaced with plausible assumptions, the models fit their data very well, and basis for their poor-fitting models becomes clear.