Mechanisms underlying fear reduction during exposure therapy remain debated. Emotional Processing Theory highlights habituation as a key mechanism, whereas Inhibitory Learning Theory emphasizes expectancy violation. The current study examined the relative contribution of habituation and expectancy updating (used as an index of expectancy violation) to fear reduction during exposure for fear of heights. 

Participants (N = 76) completed a single-session exposure intervention in either real-life or a virtual height environment. Fear of heights, habituation, and expectancy updating were assessed. These mechanisms were examined in relation to fear reduction following exposure.

Fear of heights decreased following exposure, although this reduction was not statistically significant. Expectancy updating was not associated with fear reduction, whereas greater habituation was significantly associated with larger reductions in fear of heights.

The results provide greater support for habituation-based theories of exposure than for expectancy violation-based theories in the context of the present study. Although the results should be interpreted with caution given the limitations, they suggest that allowing sufficient time for anxiety to stabilize during exposure may contribute to reductions in fear.