Experiment Structure.

Each subject performed 990 trials in total across four experimental phases. Task 1 examined subjects’ ability to estimate the mean of a jittering visual cursor, split into a training phase (1A) and a test phase (1B). In Task 2 we examined the subject’s ability to report their confidence in this estimate in addition to reporting the mean, again with a training phase (2A) and a test phase (2B). Subjects performed several sessions in each phase to improve data integrity. On each trial we presented 15 cues, distributed pseudo-randomly with variance , and split the trial into blocks, perturbing a given block in direction . We examined , and levels of each of these manipulations respectively, listed in the table. We also included trials of random duration (between 5 and 15 cues in length). For each configuration subjects performed 15 trials. All sessions and trials were randomly shuffled within a phase.