| Short arcs typically are perceived as having less curvature than longer arcs (i.e., short arcs are “perceptually flattened”), and this phenomenon has been labeled the Arc-size Illusion. This illusion was examined as it relates to the aviation domain, where planar displays often represent aircraft intent and/or history information with lines. Participants were given arcs that represented intent and history and were asked to judge the future position of aircraft. Four independent variables were employed: Length of Predictor (9, 13.5, 18, 27, 36, 54, 72, 108, and 144 deg), History (Absent and Present), Aircraft Icon (Chevron, Circle, and None), and Pulsing (Present and Absent). Error in perceived curvature yielded a function consistent with the Arc-size Illusion, suggesting the illusion has important implications in the aviation domain. Participants utilized history information only when arc sizes were relatively small. However, even with these small arcs, the data suggest that participants may not have weighted history information as heavily as predictive information. The mere presence of an icon did not have an effect on performance nor did the type of icon. However, the data suggest that the placement of the icon (Middle, End, or Absent) affected performance. Finally, Pulsing had the effect of increasing overall perceived curvature, but it did not interact with the size of the arc. |
