When nothing matters: Assessing markers of expectancy violation during omissions of threat

Over the past decade, increasing evidence has pointed to the importance of threat omissions and the associated violations of expectancy for long-term gains of extinction learning and exposure treatment. Yet, the identification of valid markers of these expectancy violations remains somewhat challenging, thereby complicating the translation of these scientific discoveries into viable therapeutic interventions. In order to fill this gap, we developed the expectancy violation assessment (EVA) task in which participants are presented with probability (0%, 25%, 50%, 75%, 100%) and intensity (weak, moderate, strong) information of an upcoming electrical stimulation, time-locked by a countdown clock. Most trials, however, did not contain the electrical stimulation and therefore constituted a violation of threat expectancies. We recorded subjective ratings of relief-pleasantness and omission-induced skin conductance responses during all omitted stimulations. As expected, both markers were lower to expected omissions (following 0% instructions) versus unexpected omissions (following non-0% instructions). Furthermore, they increased with increasing intensity instructions, and were moderately correlated on a trial-by-trial basis. These findings provide experimental validation of the EVA task as a screening model for putative markers of expectancy violation that might be useful for on-line tracking of exposure success.