Fixation-evoked potentials reveal neural signatures of hierarchical belief-updating during decision-making

Many decisions require maintaining beliefs across multiple levels of representation, from sampling and integrating information to forming action plans. To elucidate these processes and reveal the neural mechanisms supporting them under naturalistic free-viewing conditions, we combined EEG and eye-tracking in a multi-attribute choice task. Leveraging our recently developed Multi-Attribute Search and Choice (MASC) model, we generated fixation-level predictions for value-belief updating processes encompassing attribute, option, and preference states. Behavioral and eye-tracking data confirmed search and choice dynamics as predicted by MASC. Crucially, fixation-evoked potentials (FEPs) revealed distinct neural signatures along the processing hierarchy. While attribute-level and option-level updates were reflected in an early fronto-central positivity and a centro-parietal positivity, respectively, emerging preferences were expressed in lateralized motor-preparatory activity. Our preregistered study elucidates a hierarchy of neural belief-updating processes linking information sampling to decision formation and opens new research avenues for investigating neural attention and choice dynamics in naturalistic free-viewing paradigms.