RESUMEN
INTRODUCTION: Exposure may be especially effective when within exercises, there is a strong violation of threat expectancies and much opportunity for fear reduction. Outcomes of exposure may therefore improve when exposure is conducted in large steps (LargeSE) relative to small steps (SmallSE). METHODS: Children and young people with a specific phobia (SP) (N = 50, age 8-17, 64 % girls) participated in a preregistered single-blind, randomized controlled microtrial comparing LargeSE and SmallSE in a four-week baseline-treatment design. Clinical interviews, behavioral avoidance tests, and self-report measures were assessed at pre-treatment, post-treatment, and at one-month follow-up. RESULTS: Within exercises, LargeSE resulted in higher initial fear levels and more within-session expectancy violation. Nevertheless, SmallSE resulted in a larger decline of SP severity from baseline to post-treatment and follow-up, and a larger decline of anxiety and avoidance towards one's individual goal from baseline to follow-up. There were no differences between LargeSE and SmallSE regarding changes in general self-efficacy or behavioral avoidance. Although session duration was standardized and similar for both conditions, participants in SmallSE received more (shorter) exercises. DISCUSSION: SmallSE might be more effective in reducing SP severity because children in SmallSE were exposed to a larger number and variety of exercises than children in LargeSE.