Sources of confidence in value-based choice

"Which meal would you like, chicken or pasta? Chicken please. ...hmmm not sure. No sorry, I prefer pasta". Confidence, the subjective estimate of decision quality, is an essential component of decision making. It is necessary for learning from mistakes in the absence of immediate feedback and guiding future actions. Despite its importance, it remains unclear where confidence judgments originate from, especially for decisions that rely on individual subjective values and preferences. Here, we devised a behavioural paradigm and a computational framework that allowed us to formally tease apart the sources of confidence in value-based decisions. In line with canonical decision theories, we found that trial-to-trial fluctuations in the precision of value encoding impact economic choice consistency. Surprisingly, however, and contrary to canonical theories of confidence, this uncertainty has no influence on confidence reports. Instead, we find that confidence reflects the degree of balance and cognitive effort with which the choice alternatives have been compared. Specifically, we show that confidence emerges from endogenous attentional effort towards choice alternatives and down-stream noise in the comparison process. These findings caution a direct translation of canonical frameworks of confidence based on perceptual decision behavior into the value-based choice domain. In addition our computational framework provides an explanation for confidence miss-attributions in economic behaviour and reveals the mechanistic interplay of endogenous attentional states and subjective value for guiding decisions and metacognitive awareness.