title: Visual search under scotopic lighting conditions.
abstract: When we search for visual targets in a cluttered background we systematically move our eyes around to bring different regions of the scene into foveal view. We explored how visual search behavior changes when the fovea is not functional, as is the case in scotopic vision. Scotopic contrast sensitivity is significantly lower overall, with a functional scotoma in the fovea. We found that in scotopic search, for a medium- and a low-spatial-frequency target, individuals made longer lasting fixations that were not broadly distributed across the entire search display but tended to peak in the upper center, especially for the medium-frequency target. The distributions of fixation locations are qualitatively similar to those of an ideal searcher that has human scotopic detectability across the visual field, and interestingly, these predicted distributions are different from those predicted by an ideal searcher with human photopic detectability. We conclude that although there are some qualitative differences between human and ideal search behavior, humans make principled adjustments in their search behavior as ambient light level decreases.
authors.affiliation: University of Giessen, Department of Experimental Psychology, Otto-Behaghel-Str. 10F, 35394 Gießen, Germany.
authors.forename: Vivian C
authors.initials: VC
authors.lastname: Paulun
authors.affiliation: University of Giessen, Department of Experimental Psychology, Otto-Behaghel-Str. 10F, 35394 Gießen, Germany.
authors.forename: Alexander C
authors.initials: AC
authors.lastname: Schütz
authors.affiliation: Rutgers University, Department of Psychology, Piscataway, NJ 08854, United States.
authors.forename: Melchi M
authors.initials: MM
authors.lastname: Michel
authors.affiliation: University of Texas at Austin, Center for Perceptual Systems and Department of Psychology, Austin, TX 78750, United States.
authors.forename: Wilson S
authors.initials: WS
authors.lastname: Geisler
authors.affiliation: University of Giessen, Department of Experimental Psychology, Otto-Behaghel-Str. 10F, 35394 Gießen, Germany. Electronic address: gegenfurtner@uni-giessen.de.
authors.forename: Karl R
authors.initials: KR
authors.lastname: Gegenfurtner
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology*; D005133:Eye Movements / Q000502:physiology; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D005584:Fovea Centralis / Q000503:physiopathology*; D006801:Humans; D008029:Lighting; D008297:Male; D055254:Night Vision / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D014794:Visual Fields / Q000502:physiology; D055815:Young Adult
keywords: Eye movements; Scotopic sensitivity; Scotopic vision; Visual search