Missed targets are more frequent than false alarms: a model for error rates in visual search.
In many visual search tasks, reaction times (RTs) for target detection are measured as a function of display size. The corresponding error rates are usually low but increase with increasing display size. Missed-target errors are more common than false alarms. In recent models of visual search, the error rates were attributed to a premature search termination and error rates increasing with display size were interpreted as indicating a speed-accuracy trade-off and an underestimation of search times per item (obtained from RT slopes). A model is described in which errors occur as a result of imperfect rather than incomplete search (i.e., it is assumed that there are task-specific probabilities of categorizing a target or a distractor incorrectly). Signal-detection theory is used to show that the observed error rate properties can be attributed to an optimized decision strategy. "Corrections" of RT data are thus questionable.
Zenger
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Sektion Visuelle Sensorik, University Eye Clinic, Tübingen, Germany. barbara.zenger@uni-tuebingen.de
Fahle
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D006801:Humans; D008960:Models, Psychological; D011336:Probability; D011930:Reaction Time; D017603:Signal Detection, Psychological; D014796:Visual Perception