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Jeffrey B. Mulligan, Kelly S. Steelman-Allen; Conspicuity of peripheral visual alerts. Journal of Vision 2010;10(7):150. doi: 10.1167/10.7.150.
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Measurement of peripheral visibility of a target typically involves a fixating subject intently waiting for the appearance of the stimulus. In real-world environments such as aircraft cockpits and automobiles, however, the operator is usually engaged in a variety of non-monitoring tasks when visual alerting signals appear. We use the term conspicuity to distinguish the attention-getting power of a visual stimulus from simple visibility. We have developed an experimental paradigm to study visual conspicuity: subjects perform a demanding central task, in which they use a computer mouse to keep a wandering target spot in the central portion of the screen, while simultaneously monitoring a set of peripheral numeric displays for color change events. When such an event occurs, the subject must make a judgment concerning the displayed numeric value, indicating the response with a mouse click on one of two buttons located above and below the item. The strengths of the various alerts are varied within a run using a staircase procedure, allowing us to estimate noticeability thresholds. Visibility of the alerting signals is measured separately in a control experiment in which the subject fixates a location within the central task area, while monitoring the peripheral alert locations. Thresholds in the dual-task experiments are lower than would be expected based on the results of the control experiment, due to the fact that the subjects actively sample the alert locations with fixations while performing the central task. Not surprisingly, more sampling fixations are made to high-frequency alert locations. The results are modeled using N-SEEV (Steelman-Allen et al., HFES 2009), a computational model of attention and noticing that predicts visual sampling based on static and dynamic visual sampling, the bandwidth and value of information in each channel, and the subject's attentional set.
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