On the locus and time course of confidence processing

Abstract

Participants were assigned to one of two types of psychophysical tasks: signal detection or line-length discrimination. In one of three blocks of trials participants rated their confidence in the accuracy of each decision by selecting one of six confidence categories. In a second block participants never rendered confidence. In a third block participants always expected to have to render confidence, but were instructed not to do so if a tone sounded. The tone sounded on 50% of the trials at times varying from 100 to 500 ms following stimulus presentation. Primary decision reaction times increased whenever confidence was rendered. Importantly, in the stop-confidence processing signalled task, primary decision response times increased linearly as the time between the stimulus presentation and the stop-confidence signal increased. These findings are clear in implicating both a decisional and post-decisional locus for the basis of confidence. Taken together, the findings support the idea that confidence processing evolves at a constant rate over the course of primary decision processing.