title: Spatial contrast sensitivity and grating acuity of barn owls.
abstract: The eyes of barn owls (Tyto alba pratincola) display very little aberrations, and have thus excellent optical quality. In a series of behavioral experiments, we tested whether this presumably beneficial feature is also reflected at a perceptual level in this species. As fundamental indicators for visual performance, the spatial contrast sensitivity function (CSF) and grating acuity were measured in two barn owls with psychophysical techniques. Stimulus luminance was 2.7 cd/m(2). The CSF found here renders the typical band-limited, inverted U-shaped function, with a low maximum contrast sensitivity of 8-19 at a spatial frequency of 1 cyc/deg. Grating acuity was estimated from the CSF high frequency cut-off and yielded 3.0-3.7 cyc/deg. In a second experiment, in which contrast was held constant and spatial frequency was varied, grating acuity was measured directly (2.6-4.0 cyc/deg). These results put barn owls at the very low end of the visual acuity spectrum of birds, and demonstrate that visual resolution and sensitivity cannot be predicted by optical considerations alone.
authors.affiliation: Department of Zoology and Animal Physiology, RWTH Aachen, Aachen, Germany. wolf@bio2.rwth-aachen.de
authors.forename: Wolf M
authors.initials: WM
authors.lastname: Harmening
authors.forename: Petra
authors.initials: P
authors.lastname: Nikolay
authors.forename: Julius
authors.initials: J
authors.lastname: Orlowski
authors.forename: Hermann
authors.initials: H
authors.lastname: Wagner
mesh_terms: D000818:Animals; D015350:Contrast Sensitivity; D004192:Discrimination, Psychological; D008297:Male; D011601:Psychophysics; D013028:Space Perception; D020305:Strigiformes / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*; D014792:Visual Acuity