Imperfect Bayesian inference in visual perception
Fig 1
(A) Illustration of a trial in the discrimination task. Subjects reported on each trial the tilt direction of a single ellipse (“clockwise” or “counterclockwise” relative to vertical). The elongation of the stimulus could take two values. We refer to the most elongated type of ellipse as a “high reliability” stimulus and the less elongated type as a “low reliability” stimulus. Feedback was provided by briefly turning the fixation cross red (error) or green (correct) after the response was given. (B) The subject-averaged data (filled circles) and model fits (curves) reveal that sensitivity was higher for stimuli with high reliability (black) compared to those with low reliability (red). Error bars represent 1 s.e.m. (C) Illustration of a trial in the visual search task with brief stimulus presentation time. (D) Top: examples of target-present displays under the four different levels of external uncertainty. Bottom: distributions from which the stimuli in the example displays were drawn. In all four examples, the ellipse at the “north” location is a target and the other three are distractors.