Landau, H. (1951). On dominance relations and the structure of animal societies: I. Effect of inherent characteristics. Bulletin of Mathematical Biology, 13(1), 1–19.
Abstract: Abstract Societies are considered in which a non-transitive dominance relation exists between every pair of members, such as the peck-right in a flock of hens. A one-dimensional measure of the structure of such a society,h, is defined, withh=0 for equality andh=1 for the hierarchy. It is assumed that each member of the society is characterized by an ability vector whose components depend on individual characteristics such as size, concentration of sex hormone, etc., but not on social factors such as social rank. The distribution of abilities among members of the society is assumed to be given by a distribution function which is the same for all members, and the probability that one member dominates another is given by a function of the ability vectors of the two. On these assumptions formulas for the expected (mean) value and variance ofh are determined in terms of the distribution and dominance probability functions. Some special cases are calculated, especially that for normany distributed abilities and dominance probability given by the normal probability integral. Several conclusions are derived. If all members are of equal ability, so that dominance probability is 1/2, then any sizable society is much more likely to be near the equality than the hierarchy; and, as the size of the society increases, the probability that it will be near the hierarchy becomes vanishingly small. If the dominance probability is a weighted sum of several independent components, which make up the ability vector, then the society is less likely to be close to the hierarchy as the number of these components increases. The hierarchy is the prevalent structure only if unreasonably small differences in ability are decisive for dominance. From this it appears that the social factors, or psychological factors such as the previous history of dominance, which are not included in the present treatment, may be of great importance in explaining the observed prevalence of structures very close to the hierarchy in flocks of domestic hens.
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Rosenzweig, M. R. (1951). Representations of the Two Ears at the Auditory Cortex. American Journal of Physiology -- Legacy Content, 167(1), 147–158.
Abstract: This investigation is part of a more general study of binaural perception and
its electrophysiological correlates. In order to account for some of the
phenomena of binaural perception, Boring (I) proposed that the two ears
are represented at the auditory cortex by two different populations of cortical units.
We have attempted to test this hypothesis, taking up two aspects in succession:
I) Do the populations of cortical units that represent the two ears differ in
size at the two cerebral hemispheres?S timulation of either ear evokes electrophysiological
responseso ver the entire extent of the auditory cortex of both hemispheres.
It has been suggestedt hat the responsesa re larger in amplitude at the hemisphere
contralateral to the ear stimulated (2-4), but this has also been denied (5). We will
present quantitative evidence to show that at both hemispheres the response of
the contralateral ear is significantly larger than the response of the ipsilateral ear.3
2> Are the two ears represented by independent populations of cortical units,
or are they represented by overlapping populations of cortical units? Results from
a small number of experiments indicate that the two populations overlap considerably.
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ALTMANN, M. (1951). A study of behaviour in a horse-mule group. Sociometry, 14(4), 351–354.
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Antonius. O.,. (1951). Die Tigerpferde die Zebras. Momogr WildSäugetiere, II, 1–148.
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Hoffstetter R,. (1951). La structure des incisives infürieuses chez les équides modernes. Importance dans la classification des zébres couaggas. Bull Mus Hist Nat, 22, 684–692.
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Howell Ce, R. W. (1951). Environmental sources of variation in the length of the horse. J Anim Sci, 10, 789–796.
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Lundholm B,. (1951). A skull of the true quagga in the collection of the Tranvaal Museum. S Afr J Sci, 47, 307–312.
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Menzies Ji,. (1951). Man and the zebra. Oryx, 1, 127–133.
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Rzasnicki A,. (1951). Zebras and quaggas. Ann Mus Zool Polonica, 16, 203–252.
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Simpson Gg,. (1951). Horses.
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