The effect of search time on perception.

A group of 100 carefully selected chest radiographs was read by ten observers, five experienced and five inexperienced. The radiographs were chosen to present the readers with a disproportionately large number of both subtle abnormalities and nonpulmonary lesions. Each reader was allowed to search the radiographs for as long as appropriate, up to a maximum of four minutes. The length of time taken for each observation was recorded to the nearest second. The time-perception data were plotted on both linear and semilogarithmic graphs. The results showed that experienced readers concluded their visual search while positive detection rate was higher than the rate for false-positives. For lesions in the central phasic, with both a rapid and a slow component of perception. If these data are plotted on a semilogarithmic scale, each of the two components plots as a straight line. For lesions in the periphery of the radiograph (chest wall and upper abdomen), the time-perception curve is monophasic, showing only a slow component.