Decisional difficulty in pattern discrimination

To assess the relative influence of decisional ambiguity and response uncertainty on task difficulty, a pattern discrimination task was presented to 60 college undergraduates. The comparison stimuli were nine 20 X 20 matrices of randomly assigned black and white squares, with percent of black squares varying evenly from 10% to 90%. The standard contained 50% black squares. In a low-response uncertainty condition there were two response categories, and five in a high uncertainty condition. It was hypothesized that decisional ambiguity should be greatest at the boundaries between categories. The results suggested that decisional ambiguity was the critical factor determining judgment difficulty.