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Author |
Timney, B.; Keil, K. |
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Title |
Local and global stereopsis in the horse |
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Journal Article |
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Year |
1999 |
Publication |
Vision Research |
Abbreviated Journal |
Vision Res |
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Volume |
39 |
Issue |
10 |
Pages |
1861-1867 |
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Keywords |
Animals; Depth Perception/*physiology; Female; Horses/*physiology; Pattern Recognition, Visual/physiology; Psychophysics; Sensory Thresholds/physiology; Vision, Binocular/physiology; Vision, Monocular/physiology |
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Abstract |
Although horses have laterally-placed eyes, there is substantial binocular overlap, allowing for the possibility that these animals have stereopsis. In the first experiment of the present study we measured local stereopsis by obtaining monocular and binocular depth thresholds for renal depth stimuli. On all measures, the horses' binocular performance was superior to their monocular. When depth thresholds were obtained, binocular thresholds were several times superior to those obtained monocularly, suggesting that the animals could use stereoscopic information when it was available. The binocular thresholds averaged about 15 min arc. In the second experiment we obtained evidence for the presence of global stereopsis by testing the animals' ability to discriminate between random-dot stereograms with and without consistent disparity information. When presented with such stimuli they showed a strong preference for the cyclopean equivalent of the positive stimulus with the real depth. These results provide the first behavioral demonstration of a full range of stereoscopic skills in a lateral-eyed mammal. |
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Department of Psychology, Faculty of Social Science, University of Western Ontario, London, Canada. timney@julian.uwo.ca |
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0042-6989 |
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PMID:10343877 |
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yes |
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Call Number |
Equine Behaviour @ team @ |
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3580 |
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Author |
Timney, B.; Keil, K. |
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Title |
Visual acuity in the horse |
Type |
Journal Article |
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Year |
1992 |
Publication |
Vision Research |
Abbreviated Journal |
Vis. Res. |
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Volume |
32 |
Issue |
12 |
Pages |
2289-2293 |
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Keywords |
Horse Visual acuity Visual discrimination |
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Abstract |
We assessed the ease with which horses could learn visual discriminations and measured their resolution acuity. We trained three horses to press their noses against one of two large wooden panels to receive a small food reward. Following training on a series of two-choice discrimination tasks, resolution acuity was measured. Although there was some variability between animals, the best acuity obtained was 23.3 c deg-1. Within the margin of error imposed by limited anatomical data, the obtained values are consistent with predictions based on retinal ganglion cell density estimates and posterior nodal distance/axial length ratios. They suggest that the resolution acuity of the horse is limited by ganglion cell density in the temporal portion of the narrow visual streak. |
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Call Number |
refbase @ user @ |
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851 |
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