ABSTRACT

What is the orientation of an object? A simple line has an axis of orientation. That line, turned upside-down, is indistinguishable from the original line. Thus, the possible orientations of a line range from 0 to 180 deg. Most objects, however, have an axis and a polarity. A polar object, turned upside-down, looks upside-down. Accordingly, the orientations of a polar object range from 0 to 360 deg. A series of visual search experiments were run to determine if preattentive processes represent orientation in a 180 deg or a 360 framework. Results suggest that preattentive orientation is represented in 180 deg. Experiments One and Four show that search for a target rotated 90 deg from the distractors is more efficient than search for a target rotated 180 deg from the distractors. Experiments Two, Three, and Five use a variety of different stimuli to demonstrate that that search for targets rotated 180 deg from distractors is inefficient.