title: Vernier acuity in barn owls.
abstract: Vernier acuity thresholds were obtained psychophysically in three adult barn owls with vertical bars and sinusoidal gratings. A minimal displacement threshold of 0.58 arcmin was observed with the bar stimulus under binocular viewing conditions. The mean binocular bar threshold was 2.51 arcmin. Bar thresholds were lower than grating thresholds. Monocular thresholds, obtained in one bird only, were typically higher than binocular thresholds. With grating acuity being about 3.75 arcmin in this species, we conclude that the findings reported here indicate that vernier acuity is hyperacute in the barn owl. The data presented here are the first demonstration of vernier acuity thresholds in birds.
authors.affiliation: Department of Zoology and Animal Physiology, RWTH Aachen University, Kopernikusstrasse 16, 52056 Aachen, Germany. wolf@bio2.rwth-aachen.de
authors.forename: Wolf M
authors.initials: WM
authors.lastname: Harmening
authors.forename: Katrin
authors.initials: K
authors.lastname: Göbbels
authors.forename: Hermann
authors.initials: H
authors.lastname: Wagner
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D015350:Contrast Sensitivity / Q000502:physiology; D008297:Male; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D012684:Sensory Thresholds; D020305:Strigiformes / Q000502:physiology*; D015348:Vision, Binocular / Q000502:physiology; D015349:Vision, Monocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology