Specialized cingulo-opercular network activation in judging ambiguity of facial expressions in a slow reveal fMRI paradigm

Certain facial expressions express emotional valence clearly, while other expressions such as surprise are ambiguous and can be interpreted as expressing either positive or negative valence. In two studies, we presented a valence bias task in which masked clear and ambiguous emotional expressions were slowly revealed over several seconds. This design allows for investigation of the decision-making mechanisms supporting ambiguity processing as they unfold over the course of a trial. In the main study, the task was administered to 32 young adults in the fMRI environment and BOLD time courses were extracted from regions of interest in three cortical networks previously associated with task control, decision making, and performance reporting. In a follow-up study, the task was administered to a larger, online sample (n = 81) using a more extended slow reveal design with additional unmasking frames. Positive judgments of surprised faces were accompanied by stronger activation in the cingulo-opercular network and slower response times. These results support the initial negativity hypothesis, which posits that the default response to ambiguity is negative, by demonstrating that making positive judgments is an effortful, controlled process that varies according to individual biases. ### Competing Interest Statement The authors have declared no competing interest.