title: Free viewing perceptual asymmetries for judgment of brightness and quantity: dependence on stimulus orientation.
abstract: Previous research has indicated that normals exhibit strong leftward biases during free-viewing perceptual judgments of brightness and quantity. When participants view two symmetrical objects and they are forced to choose which object appears darker or more numerous, participants usually select the stimulus with the relevant feature on the left side. The present study investigated the possibility that these perceptual asymmetries are dependent on scanning a stimulus horizontally across the midline by administering a task with two rectangular reversed stimuli presented either horizontally or vertically. When the stimuli were presented horizontally (crossing the midline), participants exhibited leftward biases, but these biases disappeared when the stimuli were presented vertically. This result supports the position that free-viewing perceptual asymmetries are dependent on scanning the stimuli across the midline.
authors.affiliation: Department of Psychology, University of Saskatchewan, Saskatoon, Canada. Lorin.Elias@U.S.A.sk.ca
authors.forename: Lorin J
authors.initials: LJ
authors.lastname: Elias
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Saucier
authors.forename: Aaron
authors.initials: A
authors.lastname: Sheerin
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Burton
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007600:Judgment; D008297:Male; D010775:Photic Stimulation; D011930:Reaction Time; D011795:Surveys and Questionnaires; D014794:Visual Fields / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*