Figure 1.

Task design and performance results. A, Subjects performed two-alternative forced-choice discrimination tasks about perception and memory. In perception blocks, subjects selected the brighter of two stimuli. Memory blocks started with an encoding period and then subjects indicated in each trial which of two stimuli appeared during the encoding period. Abstract shapes and words were used as stimuli in both tasks. In confidence blocks, subjects rated their confidence and, in follow blocks, they pressed the highlighted number. B, Percentage correct responses per block type in the confidence condition. Each marker represents a subject. C, Mean percentage correct responses by domain averaged over subjects and stimulus types. Dotted lines indicate chance performance. Bars indicate SEM. n.s., Not significant; P, perception; M, memory.