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Heffner, R. S., & Heffner, H. E. (1983). Hearing in large mammals: Horses (Equus caballus) and cattle (Bos taurus). Behavioral Neuroscience, 97(2), 299–309.
Abstract: Determined behavioral audiograms for 3 horses and 2 cows. Horses' hearing ranged from 55 Hz to 33.3 kHz, with a region of best sensitivity from 1 to 16 kHz. Cattle hearing ranged from 23 Hz to 35 kHz, with a well-defined point of best sensitivity at 8 kHz. Of the 2 species, cattle proved to have more acute hearing, with a lowest threshold of –21 db (re 20 μN/m–2) compared with the horses' lowest threshold of 7 db. Comparative analysis of the hearing abilities of these 2 species with those of other mammals provides further support for the relation between interaural distance and high-frequency hearing and between high- and low-frequency hearing. (39 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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Horrocks, J. A., & Hunte, W. (1983). Rank Relations in Vervet Sisters: A Critique of the Role of Reproductive Value. Am. Nat., 122, 417–421.
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Berger J,. (1983). Predation, sex ratios, and male competition in equids. J Zool Lond, 201, 205–216.
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Wolfe, J. M. (1983). Hidden visual processes. Sci Am, 248(2), 94–103.
Abstract: Isoluminant stimulus is an image whose edges are defined only by a change in color, not by change in brightness. The stimulus here is imperfect: the blue parts and the green parts of the image are only as nearly equal in brightness as they can be on the printed page. Moreover, the change in brightness beyond the edge of the page is apparent, and so is the fact that the reader is holding the magazine at reading distance. When such cues are removed under laboratory conditions, subjects faced with an isoluminant stimulus prove unable to bring its edges into focus. This deficiency contributes to making a familiar face hard to recognize. The experiment indicates that the brain process underlying visual accommodation (the focusing of the eyes) cannot “see” color; it is a hidden process distinct from the processes that lead to perception. The image shows Groucho Marx as he appeared in the motion picture Horse Feathers.
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Crook, J. H. (1983). On attributing consciousness to animals. Nature, 303(5912), 11–14.
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Berger, J. (1983). Induced abortion and social factors in wild horses. Nature, 303(5912), 59–61.
Abstract: Much evidence now suggests that the postnatal killing of young in primates and carnivores, and induced abortions in some rodents, are evolved traits exerting strong selective pressures on adult male and female behaviour. Among ungulates it is perplexing that either no species have developed convergent tactics or that these behaviours are not reported, especially as ungulates have social systems similar to those of members of the above groups. Only in captive horses (Equus caballus) has infant killing been reported. It has been estimated that 40,000 wild horses live in remote areas of the Great Basin Desert of North America (US Department of Interior (Bureau of Land Management), unpublished report), where they occur in harems (females and young) defended by males. Here I present evidence that, rather than killing infants directly, invading males induce abortions in females unprotected by their resident stallions and these females are then inseminated by the new males.
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Ristau, C. A. (1983). Language, cognition, and awareness in animals? Ann. N.Y. Acad. Sci., 406(1), 170–186.
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