A Measure of Search Efficiency in a Real World Search Task

In visual search, preattentive processes locate potential target regions and selective attention is directed to potential target locations. The current experiments examined the role of global visual clutter in participants' ability to deploy attention to target regions containing relatively more or less local clutter. Participants searched maps of high, medium, or low global clutter for a target in a high or low local clutter region. Global and local clutter influenced search time, with larger effects of local clutter as global clutter increased. in addition, there was no effect of set size on search time. We propose that the preattentive precess of detecting regions likely to contain the target is less efficient as the amount of global clutter increases. Furthermore, in complex images and real world search tasks, global and local clutter measures can provide a good predictor of search efficiency when search set size is difficult to determine.
Submitted to the journal "Perception." Additional NRL Grant No. 55-07-01.