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Reboreda, J. C., & Kacelnik, A. (1990). On cooperation, tit-for-tat and mirros. Anim. Behav., 40(6), 1188–1189.
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Cassini, M. H., Kacelnik, A., & Segura, E. T. (1990). The tale of the screaming hairy armadillo, the guinea pig and the marginal value theorem. Anim. Behav., 39(6), 1030–1050.
Abstract: Foraging by screaming hairy armadillos, Chaetophractus vellerosus, and guinea pigs, Cavia porcellus, was studied in the laboratory. The main question was whether patch exploitation varies with overall capture rate as predicted by the marginal value theorem (MVT). Armadillos in experiment I and guinea pigs in experiment II experienced a single travel time between depleting patches of two kinds: good and poor. There were two treatments, which differed in the quality of poor patches. MVT predicts that within a treatment, more prey should be taken from good than from poor patches and between treatments, good patches should be exploited in inverse relation to the quality of poor patches and poor patches should be exploited in direct relation to their own quality. In experiment III, guinea pigs experienced three treatments which differed in the travel requirement, while the two patch types remained the same. MVT predicts that within a treatment more prey should be taken from good than from poor patches and that between treatments more prey should be taken from both patch types as travel requirement increases. The qualitative predictions were supported in the three experiments. The quantitative fit was good but there was a bias towards more severe patch exploitation than predicted. The results indicate that in these species patch exploitation depends on overall food availability as predicted by the MVT when overall food availability differs either because of patch type composition or because of differences in travel requirement between patches.
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Hemelrijk, C. K. (1990). Models of, and tests for, reciprocity, unidirectionality and other social interaction patterns at a group level. Anim. Behav., 39(6), 1013–1029.
Abstract: Research on reciprocity is impaired by confusing definitions and often wrongly used statistical tests. Here, two models of the mechanism on which reciprocity may be based are discussed and an initial step towards a new fremework for its analysis is presented. A distinction is made between reciprocity and interchange. In the case of reciprocity, for one kind of act the same kind is received in return. In interchange, however, two different kinds of acts are bartered. Three types of reciprocity/interchange in social actions among all pairs of group-members are distinguished ([`]qualitative', [`]relative' and [`]absolute') on the basis of the precision of the reciprocity/interchange. Permutation procedures for association between matrices (such as the Mantel Z and two other newly derived tests) are used as a statistical test for detecting reciprocity/interchange. A rough comparison of the power of the two new tests is included. The tests can be applied to all kinds of group-living animals and to all sorts of social behaviour. The distinction between the three types of reciprocity/interchange and the matching statistical methods are also useful for defining and detecting other patterns in social interactions, like unidirectionality and associations between different kinds of social behaviour. The influence on social interactions of variables like dominance rank, age and sex can be analysed in the three forms by testing correlations between invented matrices which represent the influence of these variables (the so-called hypothesis matrices) and social interaction matrices. These methods are extended for two categories of individuals, thus allowing the investigation of, for example, reciprocity between males and females. The methods are illustrated with examples of coalition formation and grooming behaviour among captive chimpanzees, Pan troglodytes.
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Edgar, G. K., & Smith, A. T. (1990). Hemifield differences in perceived spatial frequency. Perception, 19(6), 759–766.
Abstract: Measurements of the perceived spatial frequency of stationary sinewave gratings were made with the gratings presented at the same eccentricity in the left, right, upper, and lower visual hemifields. Ten subjects performed the task binocularly with spatial frequencies of 1, 2, and 4 cycles deg-1. Two of these subjects also performed the task monocularly at 2 cycles deg-1. In the majority of cases, the spatial frequency of stimuli presented in the left and lower visual hemifields was overestimated relative to stimuli presented in the right and upper visual hemifields. The results were similar for all spatial frequencies tested, and the direction of the asymmetry was the same whether viewing was with the left eye, right eye or binocular, suggesting that the differences in perceived spatial frequency are not retinal in origin.
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Houpt, K. A., Zahorik, D. M., & Swartzman-Andert, J. A. (1990). Taste aversion learning in horses. J. Anim Sci., 68(8), 2340–2344.
Abstract: The ability of ponies to learn to avoid a relatively novel food associated with illness was tested in three situations: when illness occurred immediately after consuming a feed; when illness occurred 30 min after consuming a feed; and when illness was contingent upon eating one of three feeds offered simultaneously. Apomorphine was used to produce illness. The feeds associated with illness were corn, alfalfa pellets, sweet feed and a complete pelleted feed. The ponies learned to avoid all the fees except the complete feed when apomorphine injection immediately followed consumption of the feed. However, the ponies did not learn to avoid a feed if apomorphine was delayed 30 min after feed consumption. They could learn to avoid alfalfa pellets, but not corn, when these feeds were presented with the familiar “safe foods,” oats and soybean meal. Ponies apparently are able to learn a taste aversion, but there were constraints on this learning ability. Under the conditions of this study, they did not learn to avoid a food that made them sick long after consumption of the food, and they had more difficulty learning to avoid highly palatable feeds.
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Hinrichs, K., Watson, E. D., & Kenney, R. M. (1990). Granulosa cell tumor in a mare with a functional contralateral ovary. J Am Vet Med Assoc, 197(8), 1037–1038.
Abstract: A functional corpus luteum was found in the ovary contralateral to the ovary with a granulosa cell tumor in a 24-year-old Standardbred mare. The mare was ovariectomized because she was to be used as a jump mare for collection of semen from stallions. The blood concentration of progesterone was 2.2 ng/ml, and the luteal tissue progesterone concentration was 6.3 micrograms/mg. Atrophy of the contralateral ovary is one of the major signs used in diagnosis of granulosa cell tumor; however, our findings indicate that the ovary contralateral to a granulosa cell tumor is not invariably nonfunctional.
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Charles T. Snowdon,. (1990). Language capacities of nonhuman animals. American Journal of Physical Anthropology, 33(S11), 215–243.
Abstract: In the last two decades, the study of language parallels in nonhuman animals has generated considerable controversy and excitement. Many have perceived demonstrations of linguistic skills in nonhuman animals as a threat to human uniqueness, whereas others have been uncritical of claims for complex cognitive skills in animals. Two different paradigms for studying linguistic parallels have appeared. One approach teaches great apes linguistic analogues of human language using signs or arbitrary symbol systems; the other seeks to decode communicative complexity in the natural languages of nonhuman animals. This paper reviews the language analogue studies with great apes and cetaceans, examining the utility of the different methods and reviewing the animals' accomplishments. Studies of ontogeny, syntax, referential communication, audience effects, and perception of vocalizations in the natural communication of birds, squirrels, and primates are evaluated. Finally, the brain mechanisms underlying human speech and language are compared with those involved in vocal communication in nonhuman primates. Although chimpanzees and bonobos have accomplished much, they do not threaten human uniqueness with respect to speech and language. Many of the claims for language paralleles in natural communication systems of nonhuman animals are weak, and many can be interpreted without recourse to cognitive constructs. Whereas there exist many similarities between subcortical controls of language and of animal vocalizations, there are no parallels to Broca's and Wernicke's areas in monkeys. However, the critical studies have not been done.
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