Facing Uncertainty: A Comparison of Hierarchical and Variable Exposure Interventions for Contamination Fear

Consistent with the inhibitory retrieval approach, one proposed modification to improve the effectiveness of exposure-based interventions is to maximize variability by not proceeding linearly up an exposure hierarchy. Accordingly, the present study compares hierarchical and variable exposure interventions for contamination-fearful individuals and examines the role of uncertainty to predict intervention outcomes. Participants (N=73) were randomly assigned to complete a single-session exposure intervention using a standard hierarchy or a variable exposure intervention in which hierarchy items were randomly presented. Participants completed a behavioral approach task (BAT) at baseline and two follow-up visits over a two-week period. Both interventions resulted in a significant decrease in anxiety and disgust as well as more BAT steps completed but did not differ from one another. However, individuals in the variable exposure condition reported less variability in uncertainty during exposure compared to those in the standard condition, d=.78. Furthermore, lower levels of variability in uncertainty predicted greater reductions in anxiety and disgust post-intervention. Consistent with previous studies, variable exposure did not convey additional benefit over standard, hierarchical exposure. The experience of uncertainty during exposure is an important yet understudied process that warrants additional investigation.