Inferring cortical networks underlying human decision making Marios G. Philiastides University of Glasgow Single-unit electrophysiology studies in animals have consistently reported decision-related activity mirroring a process of temporal accumulation of sensory evidence to a fixed internal decision boundary. To date, our understanding of how response patterns seen in single-unit data manifest themselves at the macroscopic level of brain activity obtained from human neuroimaging data remains limited. Using single-trial analysis of high-density human electroencephalography data, coupled with computational modelling we show that population responses on the scalp reflect the superposition of signals associated with sensory evidence accumulation and other decision-related signals such as choice confidence. Exploiting the trial-to-trial variability in the neural code we decouple these signals and demonstrate that they exert independent leverage on behaviour. Crucially, we also show that decision confidence forms an integral part of the decision process itself rather than reflecting a purely post- decisional signal as suggested by long-standing psychological theories of metacognition.