An automatic domain-general error signal is shared across tasks and predicts confidence in different sensory modalities.

Understanding the ability to self-evaluate decisions is an active area of research. This research has primarily focused on the neural correlates of self-evaluation during visual-tasks, and whether neural correlates before or after the primary decision contribute to self-reported confidence. This focus has been useful, yet the reliance on subjective confidence reports may confound our understanding of key every-day features of metacognitive self-evaluation: that decisions must be rapidly evaluated without explicit feedback, and unfold in a multisensory world. These considerations led us to hypothesise that an automatic domain-general metacognitive signal may be shared between sensory modalities, which we tested in the present study with multivariate decoding of electroencephalographic (EEG) data. Participants (N=21, 12 female) first performed a visual task with no request for self-evaluations of performance, prior to an auditory task that included rating decision confidence on each trial. A multivariate classifier trained to predict errors in the speeded visual-task generalised to distinguish correct and error trials in the subsequent non-speeded auditory discrimination. This generalisation did not occur for classifiers trained on the visual stimulus-locked data and further predicted subjective confidence on the subsequent auditory task. This evidence of overlapping response-locked neural activity provides evidence for automatic encoding of confidence independent of any explicit request for metacognitive reports, and a shared basis for metacognitive evaluations across sensory modalities.Significance Statement Understanding the neural basis of self-evaluation is an important and active area of research. Here we show that neural activity following speeded responses in a visual task can predict accuracy in a later auditory judgment. This neural activity further generalised to predict confidence in the later auditory decision. This automatic encoding of self-evaluation that is shared between sensory modalities is of theoretical and practical importance, for identifying a domain-general marker of confidence that can improve our understanding of human decision making.