Theall, L. A., & Povinelli, D. J. (1999). Do chimpanzees tailor their gestural signals to fit the attentional states of others? Anim. Cogn., 2(4), 207–214.
Abstract: The use of vocalizations and tactile gestures by seven juvenile chimpanzees was experimentally investigated. The subjects interacted with an experimenter who typically handed them food rewards. In some trials, however, the experimenter waited 20 s before doing so. In these trials the experimenter's eyes were either open or closed, or the experimenter was either looking away from the subject or looking directly at him/her inquisitively with head movements. Although the chimpanzees produced at least one of the non-visual gestures mentioned (touching/tapping the experimenter or vocalizing) in 72% of all experimental trials, these actions and vocalizations were deployed without regard to the attentional state of their potential recipient, despite evidence that the subjects noticed the postures that defined the experimenter's attentional state. The results are discussed in the context of the distinction between the evolution of an understanding of seeing/attention as an internal mental state versus an understanding of behavioral postures alone.
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Werner, C. W., & Rehkämper, G. (1999). Discrimination of multidimensional geometrical figures by chickens: categorization and pattern-learning. Anim. Cogn., 2(1), 27–40.
Abstract: Japanese bantam hens were trained to discriminate between geometrical figures varying along four integral dimensions. Only one dimension predicted food: selections of sharp-cornered figures were reinforced, while selections of rounded figures were not. In experiment 1, hens were subsequently trained to discriminate between nine figure pairs in a simultaneous discrimination task. Because single pairs contained multiple redundant cues, whereas the relevant dimension was obvious only across stimulus pairs, the results revealed effects of both generalization and reversal learning. Accordingly, learning speed was enhanced for later discriminations. Experiment 2 tested the hens“ transfer performance to unknown pairs, following experience of 9 or 18 figure pairs. Four of seven hens showed reliable transfer after experience with 9 figures, but only three showed transfer after experience with 18 figures, indicating lower transfer with higher number of stimulus pairs learned. In experiment 3, hens were trained to discriminate 27 figure pairs. Discrimination ratios further decreased and the groups of pairs differed significantly in their ratios of discrimination. Individual hens” pecking behaviour was analysed in relation to each dimension of single figures and in relation to relative differences in the levels of dimensions between paired figures. Hens were shown to be oriented towards irrelevant information and more towards relational and configurational than elemental and dimensional aspects. The results are discussed in the biological context of individual recognition in chickens" dominance hierarchies, in which we suppose that chickens identify individual flock mates by representation of their visual pattern rather than by single characteristics.
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Griffiths D., Dickinson A., & Clayton N. (1999). Episodic memory: what can animals remember about their past? Trends. Cognit. Sci., 3, 74–80.
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Hanggi, E. B. (1999). Interocular transfer of learning In horses (Equus caballus). J Equine Vet Sci, 19(8), 518–524.
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Lejeune, H., Macar, F., & Zakay, D. (1999). Attention and timing: dual-task performance in pigeons. Behav. Process., 45(1-3), 141–157.
Abstract: Pigeons were exposed to an analog of a `dual-task' procedure used to test attentional models of timing in humans. After separate training on an auditory duration discrimination and on a variable ratio (VR) schedule, VR episodes lasting for 5 s were superimposed on the stimuli to be timed, either early (E) or late (L) during the trial. Trials with VR yielded underestimation of the target durations (increased % of `short' choices), relative to trials without VR, and this effect was stronger under the L than under the E condition. Data were similar to those collected with humans and support attentional models of timing according to which the simultaneous non-timing task uses processing resources which are diverted from the timing mechanisms.
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DUNN, L. J. (1999). PRELIMINARY INVESTIGATION OF EQUINE LEARNING AND MEMORY.
Abstract: ABSTRACT
Six horses demonstrated observation and discrimination learning and memory ability. The purpose of this study was to gain further knowledge in the area of equine learning. Performance on each task was compared in a single subject design. Subjects learned to discriminate between a black and a white bucket. The criterion for learning was set at 80% correct black bucket choice. All subjects successfully performed the discrimination task by the eighth session. Observation learning was unsuccessful; no subject reached the 80% correct criterion. Five horses were tested for memory retention of the discrimination task three weeks after the initial learning. All subjects performed the discrimination by the second session of two. These data support existing results from similar learning and memory tasks.
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Hanggi, E. B. (1999). Categorization Learning in Horses (Equus caballus). J. Comp. Psychol., 113(3), 243–252.
Abstract: Categorization learning was investigated in 2 horses (Equus caballus). Both horses learned to select a 2-dimensional black stimulus with an open center instead of a filled stimulus in a 2-choice discrimination task. After a criterion of 10 out of 10 correct responses in a random series for 2 consecutive sessions was reached, 15 additional pairs of open-center versus filled stimuli were tested. Each was run to criterion and then incorporated into sessions of randomly mixed problems. Both horses solved the 1st problem by simple pattern discrimination and showed evidence of categorical processing for subsequent problems. New pairs were learned with few or no errors, and correct responses on novel trials were significantly above chance. These results suggest that the horses were making their selections on the basis of shared characteristics with the training stimuli and were using categorization skills in problem solving.
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Rendall, D. (1999). Review of Machiavellian Intelligence II: Extensions and Evaluations. Ethology, 105(2), 178–182.
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Wingfield, J. C.,, & Ramenofsky, M. (1999). Hormones and the behavioral ecology of stress. In P. H. M. Balm (Ed.), Stress physiology in animals. (pp. 1–51). Sheffield, United Kingdom: Sheffield Academic Press.
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Weckerly, F. W. (1999). Social bonding and aggression in female Roosevelt elk. Can J Zool, 77(9), 1379–1384.
Abstract: Abstract: The relationship between degree of social bonding (extent of association among individuals) and level of aggression in ruminants is unclear. I examined social bonding and aggression in three groups of female Roosevelt elk (Cervus elaphus roosevelti) over 2 years. I hypothesized that when animals are socially bonded, bouts of aggression will be won by the individual initiating the aggression, occur quickly, and involve little physical contact, and the level of aggression does not correlate with group size. The degree of social bonding was high among individuals in all groups. Dyads of known individuals were together >80% of the time. A permutation analysis indicated that groups with the observed sizes had <0.001 chance of random association, except on one occasion when the probability was 0.72 for one group. Using focal-animal sampling, aggressive interactions were won 72% of the time by the initiator, occurred quickly (<5 s), and involved little physical contact, and the level of aggression was not correlated with group size. The level of aggression was, however, significantly lower in one of the groups. This group may have had access to more abundant food resources than the other groups. Socially bonded elk conducted aggressive interactions in a fashion that did not disrupt social stability. Résumé : La relation entre le degré de liaison sociale (importance des associations entre individus) et l`agressivité n`est pas claire chez les ruminants. J`ai étudié les liaisons sociales et l`agressivité chez trois groupes de femelles du Cerf de Roosevelt (Cervus elaphus roosevelti) pendant 2 ans. J`ai posé en hypothèse que, chez les animaux liés socialement, la victoire devrait être emportée par l`individu qui entreprend l`agression, l`agression devrait être de courte durée, se faire avec peu de contacts physiques et la fréquence des agressions ne devrait pas être liée à la taille du groupe. Des paires d`individus passaient plus de 80% de leur temps ensemble. Une analyse des permutations a démontré que, chez les groupes des tailles observées, la probabilité d`une association aléatoire était de moins de 0,001, sauf en un cas où cette probabilité a été évaluée à 0,72 chez un groupe. Par échantillonnage directionnel, j`ai observé que les interactions agressives étaient gagnées par l`individu attaquant 72% du temps, étaient de courte durée (<5 s), se faisaient avec peu de contacts physiques et leur fréquence n`était pas reliée à la taille du groupe. Il y avait cependant moins d`agressivité chez l`un des groupes. Il se peut que ce groupe ait eu accès à plus de ressources alimentaires que les autres. Chez les cerfs liés par des liens sociaux, l`agressivité ne se manifeste pas de façon à déséquilibrer la stabilité sociale.
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