Target Uncertainty and Visual Scanning Strategies

Abstract

In the past, investigations into the effects of target uncertainty on search times have been confined to tasks where the stimulus material is carefully structured. The results have been interpreted in terms of models of pattern recognition. In this paper target uncertainty was studied in tasks where subjects could exert greater freedom in determining their scanning strategies. With eye movement recording, it was established that skewed distributions of search times are obtained even when subjects adopt comparatively systematic strategies. There was no evidence that processing time, as reflected in eye fixation times, was generally lengthened with increase in target uncertainty. The observed effects of target uncertainty were discussed in relation to how subjects attempt to overcome the problem of searching simultaneously for targets of different conspicuity.