Figure 1. Auditory change detection task with confidence report showing the sequence of events for each trial:

A trial began when the center port was illuminated, cuing subjects to insert their finger. Once the finger was inserted, a stream of auditory clicks began to play. The clicks were generated by a Poisson process with a generative baseline click rate of 50 Hz. 30% of trials were catch trials with no change in the generative click rate. In the other 70% of trials, the generative click rate increased by 10, 30, or 50 Hz at a random point (red arrow in example). Subjects had to withdraw their finger within 800 ms of the change for the trial to qualify as a hit on change trials, or withhold a response for the trial to qualify as a CR on catch trials. At the end of the trial (after response or stimulus end), the two peripheral ports illuminated, cuing subjects to indicate confidence in their decision: engaging the left port reported low confidence while engaging the right reported high confidence. Immediately following the confidence report, feedback was given via an auditory tone to indicate success or failure on that trial.