Cognitive inertia threatens the validity of the implicit asssociation test

The authors review the Implicit Association Test (IAT), its use in marketing, and the methodology and validity issues surrounding it. They focus then on a validity problem that has not been investigated so far, the impact of cognitive inertia on IAT-effects. Cognitive inertia denotes the difficulty in switching from one categorization rule to the opposite categorization rule. This difficulty causes IAT-effects to depend on the order in which the two IAT-blocks are administered. In study 1, an IAT-effect is observed when the ‘compatible’ block precedes the ‘incompatible’ block, but not when the ‘compatible’ block follows the ‘incompatible’ block. In studies 2 and 3, the IAT-effect changes its sign when the order of the blocks is reversed. Cognitive inertia distorts individual IAT-scores and diminishes correlations between IAT-scores and predictor variables when block-order is counterbalanced between-subjects. Study 4 shows that counterbalancing block-order repeatedly within-subjects can eliminate cognitive inertia effects on the individual level. The authors conclude that researchers should either interpret IAT-scores on the aggregate level or, when individual IAT-scores are of interest, counterbalance block-order repeatedly within-subjects.