title: Which end is up? Two representations of orientation in visual search.
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 degrees. 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 degrees. A series of visual search experiments were run to determine if preattentive processes represent orientation in a 180 or a 360 degrees framework. Results suggest that preattentive orientation is represented in 180 degrees. Experiments 1 and 4 show that search for a target rotated 90 degrees from the distractors is more efficient than search for a target rotated 180 degrees from the distractors. Experiments 2, 3, and 5 use a variety of different stimuli to demonstrate that search for targets rotated 180 degrees from distractors is inefficient.
authors.affiliation: Harvard Medical School, Boston, MA, USA. wolfe@search.bwh.harvard.edu
authors.forename: J M
authors.initials: JM
authors.lastname: Wolfe
authors.forename: N L
authors.initials: NL
authors.lastname: Klempen
authors.forename: E P
authors.initials: EP
authors.lastname: Shulman
mesh_terms: D001288:Attention; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D010364:Pattern Recognition, Visual / Q000502:physiology; D011601:Psychophysics; D011930:Reaction Time; D012399:Rotation