Is Consistent Mapping Necessary for High-Speed Search?

Recent research has suggested that visual-search functions will become shallower with practice, but only if the stimuli and responses are consistently mapped. We tested the necessity of consistent mapping for the phenomenon by asking subjects to report the largest digit in a visual display. Despite the fact that we used a varied-mapping task, significant reduction in the visual search function was observed. The reduction could not be attributed to the probability information in the task. Perfectly consistent mapping of stimulus to response does not appear to be a necessary precondition for reduction of visual-search rate.