Type-1 and Type-2 decisions feature computational noise of similar magnitude

Mouncng evidence supports the existence of Type-2, metacognicve noise that affects human confidence judgments. The existence of this noise has led to the hypothesis that metacognicve judgments arise from a metacognicve system that is separate from the decision-making system responsible for Type-1 decisions. However, Type-2 decisions are more complex than standard Type-1 decisions, as they require evaluacng whether the strength of sensory evidence juscfies a high level of confidence. Here, we invescgated whether Type-2 computaconal noise scll exceeds Type-1 computaconal noise when judgments are matched on complexity. Subjects (N=319) performed a simple perceptual discriminacon task and in different condicons provided Type-2 confidence judgments or Type-1 judgments based on biased expectacons or unequal rewards. All of these judgments require a similar fine-grained evaluacon of the strength of sensory evidence and result in equivalent criterion placement, thus making their level of complexity more closely matched. We first confirmed that the confidence and expectacon condicons resulted in similarly biased criteria, suggescng that these judgments were indeed of comparable complexity. Criccally, both simple signal deteccon analyses and formal computaconal modeling confirmed that the confidence and expectacon condicons exhibited comparable levels of computaconal noise. In contrast, the reward condicons exhibited both less biased criteria and smaller computaconal noise. These findings demonstrate that Type-1 and Type-2 decisions of matched complexity exhibit computaconal noise of similar magnitude. More generally, our results have implicacons for the debate on whether Type-1 and Type-2 decisions are made by separate systems.