The ARC-Size Illusion as Applied to Planar Displays of Aircraft Traffic Inforamtion

Abstract

Shorter arcs are perceived as having less curvature (i.e., they are “perceptually flattened”), and this phenomenon has been labeled the Arc-size Illusion. This illusion was explored as it relates to planar displays of traffic information. Such displays often represent intent and/or history information with lines. Participants were presented with aircraft traveling on curvilinear paths, and their estimations of future aircraft location were examined. There were three major findings from the study. First, the data suggest that “perceptual flattening” and the Arc-size Illusion do indeed affect predictive judgments about aircraft on curvilinear paths. Second, and most surprising, the data suggest that increasing the size of the arc with a history line does NOT lessen “perceptual flattening.” Third, the data suggest that “perceptual flattening” is especially pronounced when predictor length is relatively short and the judgment location is relatively far. However, the effect of the predictor length essentially disappears when the judgment location is at a distance that is proportional to the predictor length.