Accuracy and Certitude in the Discrimination of Visual Number

摘要

The COMMAND SYSTEMS Task is conducting several projects to determine how accuracy of information assimilation from displays of the type used in tactical operation centers and the certitude the viewer has about this accuracy vary jointly and separately as a function of the manipulation of various information presentation variables. There is little in the literature bearing directly on this area of inquiry, although several studies over the years have involved numerousness (discrimination of visual number) for tachistoscopically presented stimuli in which performance data, and sometimes certitude data, were obtained (Kaufman, Lord, Reese, and Volkman, 1949; Minturn and Reese, 1951; Saltzman and Garner, 1948; Taves, 1941). A common finding from these studies seems to be that estimates of number of things presented and certitude plotted as a function of the actual number of things presented are in effect discontinuous functions with the break in continuity occurring between 6 and 8 things presented. Such a finding has given rise to the postulation of at least two distinct mechanisms: subitizing (immediate apprehension) and estimating. A third category, counting, is excluded as a mechanism in such brief exposures.