Abstract
Pupils tend to dilate in response to surprising events, but whether these responses are primarily stimulus driven or instead reflect a more nuanced relationship between pupil-linked arousal systems and cognitive expectations is not known. Using an auditory adaptive decision-making task, we show that evoked pupil diameter is modulated more strongly by violations of learned, top-down expectations than by changes in low-level stimulus properties. We further show that both baseline and evoked pupil diameter is modulated by the degree to which individual subjects use these violations to update their subsequent expectations, as reflected in the complexity of their updating strategy. Together these results demonstrate a central role for cognitive processing in how arousal systems respond to new inputs and, via our complexity-based analyses, provide a unified framework for understanding these effects in terms of both inference processes aimed to reduce belief uncertainty and more traditional notions of mental effort.
Footnotes
↵* co-first authors








