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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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Address |
Department of Psychology, Faculty of Social Science, University of Western Ontario, London, Canada. timney@julian.uwo.ca |
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English |
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ISSN |
0042-6989 |
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Notes |
PMID:10343877 |
Approved |
yes |
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Call Number |
Equine Behaviour @ team @ |
Serial |
3580 |
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Author |
Crystal, J.D. |
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Title |
Systematic nonlinearities in the perception of temporal intervals |
Type |
Journal Article |
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Year |
1999 |
Publication |
Journal of Experimental Psychology. Animal Behavior Processes |
Abbreviated Journal |
J Exp Psychol Anim Behav Process |
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Volume |
25 |
Issue |
1 |
Pages |
3-17 |
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Keywords |
Animals; *Attention; Awareness; Discrimination Learning; Male; Neural Networks (Computer); *Nonlinear Dynamics; Rats; Rats, Sprague-Dawley; Sensory Thresholds; *Time Perception |
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Abstract |
Rats judged time intervals in a choice procedure in which accuracy was maintained at approximately 75% correct. Sensitivity to time (d') was approximately constant for short durations 2.0-32.0 s with 1.0- or 2.0-s spacing between intervals (n = 5 in each group, Experiment 1), 2.0-50.0 s with 2.0-s spacing (n = 2, Experiment 1), and 0.1-2.0 s with 0.1- or 0.2-s spacing (n = 6 in each group, Experiment 2). However, systematic departures from average sensitivity were observed, with local maxima in sensitivity at approximately 0.3, 1.2, 10.0, 24.0, and 36.0 s. Such systematic departures from an approximately constant d' are predicted by a connectionist theory of time with multiple oscillators and may require a modification of the linear timing hypothesis of scalar timing theory. |
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Address |
Department of Psychology, Brown University, USA. jdcrys@facstaff.wm.edu |
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English |
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ISSN |
0097-7403 |
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Notes |
PMID:9987854 |
Approved |
no |
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Call Number |
Equine Behaviour @ team @ |
Serial |
2776 |
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