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Templeton, J. J. (1998). Learning from others' mistakes: a paradox revisited. Anim. Behav., 55(1), 79–85.
Abstract: Some researchers have reported the paradoxical finding of enhanced social learning when naive observers learn from unskilled rather than skilled demonstrators, particularly in discrimination tasks. In two experiments with starlings,Sturnus vulgaris, I considered whether this enhanced learning is because the observer (1) sees incorrect responses only, (2) sees both correct and incorrect responses or (3) sees an increase in the proportion of correct responses over trials. In experiment 1, individual starlings observed a demonstrator bird perform multiple simultaneous discrimination tasks. In one group, the demonstrator always picked the correct stimulus; in another group, the demonstrator always picked the incorrect stimulus; in a third group, the demonstrator consistently picked the correct stimulus 50% of the time. Those subjects that observed only incorrect choices performed significantly better than the other two groups, but none of the birds achieved the 90% correct performance criterion. Experiment 2 involved a single discrimination task; thus, a fourth group was added to control for individual learning. Again, subjects that observed only incorrect responses learned the discrimination significantly more quickly than the other three groups. Subjects that observed the demonstrator make both correct and incorrect responses were equally likely to select the same (correct) or opposite (incorrect) stimulus when the demonstrator picked the correct stimulus. When the demonstrator picked the incorrect stimulus, however, these subjects were significantly more likely to pick the opposite (correct) stimulus. These findings suggest that when learning a discrimination problem, observing a foraging companion's lack of success is more informative than observing its success.
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Summerley, H. L., Thomason, J. J., & Bignell, W. W. (1998). Effect of rider and riding style on deformation of the front hoof wall in warmblood horses. Equine Vet J Suppl, (26), 81–85.
Abstract: A rider modifies the weight distribution and dynamic balance of the horse. But what effect does a rider have on the mechanical behaviour of the hoof during each stance phase? Does riding style have any effect on this behaviour? We attempted to answer these questions using strains recorded from 5 rosette strain gauges glued to the surface of the front hooves of 4 Warmblood horses. Comparisons were made between strains with and without a rider, and when the rider was sitting, rising at a trot, or in a forward seated position. The change in strains from trot to lead or nonlead at a canter, and the effect of turning were also studied. Changing lead at a canter had as least as much effect on strain magnitudes as did turning; strains were up to 43% higher for the nonlead foot, but with little redistribution. Perhaps surprisingly, strains were significantly lower on the quarters by up to 30% with a rider than without, with a 10% increase or decrease at the toe, depending on the individual. Riding style changed strain magnitudes by up to 20% and also caused strain redistribution: strains were higher medially for sitting, and laterally for forward seat, with strains for a rising trot being more evenly distributed and intermediate in magnitude. Studying the range of, and causes of variation in hoof wall strain gives baseline data aimed, in the long term, at providing a biomechanical definition of hoof balance.
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Potts, R. (1998). Variability selection in hominid evolution. Evol. Anthropol., 7(3), 81–96.
Abstract: Variability selection (abbreviated as VS) is a process considered to link adaptive change to large degrees of environment variability. Its application to hominid evolution is based, in part, on the pronounced rise in environmental remodeling that took place over the past several million years. The VS hypothesis differs from prior views of hominid evolution, which stress the consistent selective effects associated with specific habitats or directional trends (e.g., woodland, savanna expansion, cooling). According to the VS hypothesis, wide fluctuations over time created a growing disparity in adaptive conditions. Inconsistency in selection eventually caused habitat-specific adaptations to be replaced by structures and behaviors responsive to complex environmental change. Key hominid adaptations, in fact, emerged during times of heightened variability. Early bipedality, encephalized brains, and complex human sociality appear to signify a sequence of VS adaptations—i.e., a ratcheting up of versatility and responsiveness to novel environments experienced over the past 6 million years. The adaptive results of VS cannot be extrapolated from selection within a single environmental shift or relatively stable habitat. If some complex traits indeed require disparities in adaptive setting (and relative fitness) in order to evolve, the VS idea counters the prevailing view that adaptive change necessitates long-term, directional consistency in selection. © 1998 Wiley-Liss, Inc.
Keywords: variability selection; hominids; environment; adaptation; natural selection; evolution
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Call, J., Hare, B. A., & Tomasello, M. (1998). Chimpanzee gaze following in an object-choice task. Anim. Cogn., 1(2), 89–99.
Abstract: Many primate species reliably track and follow the visual gaze of conspecifics and humans, even to locations above and behind the subject. However, it is not clear whether primates follow a human's gaze to find hidden food under one of two containers in an object-choice task. In a series of experiments six adult female chimpanzees followed a human's gaze (head and eye direction) to a distal location in space above and behind them, and checked back to the human's face when they did not find anything interesting or unusual. This study also assessed whether these same subjects would also use the human's gaze in an object-choice task with three types of occluders: barriers, tubes, and bowls. Barriers and tubes permitted the experimenter to see their contents (i.e., food) whereas bowls did not. Chimpanzees used the human's gaze direction to choose the tube or barrier containing food but they did not use the human's gaze to decide between bowls. Our findings allowed us to discard both simple orientation and understanding seeing-knowing in others as the explanations for gaze following in chimpanzees. However, they did not allow us to conclusively choose between orientation combined with foraging tendencies and understanding seeing in others. One interesting possibility raised by these results is that studies in which the human cannot see the reward at the time of subject choice may potentially be underestimating chimpanzees' social knowledge.
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Byrne, T., Sutphin, G., & Poling, A. (1998). Acquisition, extinction, and reacquisition of responding with delayed and immediate reinforcement. Behav. Process., 43(1), 97–101.
Abstract: The present study investigated acquisition, extinction, and reacquisition of free-operant responding when rats' lever presses produced water after a resetting delay of 0, 10, 20, or 30 s. Results indicated that: (1) responding was acquired rapidly at all delays without shaping or autoshaping; (2) resistance to extinction was directly related to delay length and inversely related to intermittency of reinforcement; (3) responding acquired with delayed reinforcement recovered less rapidly from extinction, and was less efficient, than responding acquired with immediate reinforcement. Comparing these results with those of studies using discrete-trials and free-operant procedures with no reinforcement delay suggest that the specific conditions under which behavior is maintained determines, in part, the behavioral effects of delay and intermittency of reinforcement.
Keywords: Acquisition; Delayed reinforcement; Extinction; Rats
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Westergaard, G. C., Liv, C., Chavanne, T. J., & Suomi, S. J. (1998). Token-mediated tool-use by a tufted capuchin monkey (Cebus apella). Anim. Cogn., 1(2), 101–106.
Abstract: This research examined token-mediated tool-use in a tufted capuchin monkey (Cebus apella). We conducted five experiments. In experiment 1 we examined the use of plastic color-coded chips to request food, and in experiments 2-5 we examined the use of color-coded chips to request tools. Our subject learned to use chips to request tools following the same general pattern seen in great apes performing analogous tasks, that is, initial discrimination followed by an understanding of the relationship among tokens, tools, and their functions. Our findings are consistent with the view that parallel representational processes underlie the tool-related behavior of capuchins and great apes.
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Klingel, H. (1998). Observations on social organization and behaviour of African and Asiatic Wild Asses (Equus africanus and Equus hemionus). Appl Anim Behav Sci, 60(2), 103–113.
Abstract: 1This paper appears with kind permission of Verlag Paul Parey, Berlin and Hamburg. It was originally published in Z. Tierpsychol., 44, 323-331 (1977), ISSN 0044-3573/ASTM-Coden: ZETIAG.1
Abstract African and Asiatic Wild Asses (Equus africanus and Equus hemionus) live in unstable groups or herds of variable composition. Some of the adult stallions are territorial in large territories in which they tolerate other ♂♂. The territorial ♂♂ are dominant over all their conspecifics |
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Fiorito, G., Biederman, G. B., Davey, V. A., & Gherardi, F. (1998). The role of stimulus preexposure in problem solving by Octopus vulgaris. Anim. Cogn., 1(2), 107–112.
Abstract: Octopus vulgaris is able to open transparent glass jars closed with plastic plugs and containing live crabs. The decrease in performance times for removing the plug and seizing the prey with increasing experience of the task has been taken to indicate learning. However, octopuses' attack behaviors are typically slow and variable in novel environmental situations. In this study the role of preexposure to selected features of the problem-solving context was investigated. Although octopuses failed to benefit from greater familiarity with the training context or with selected elements of the task of solving the jar problem, the methodological strategies used are instructive in potentially clarifying the role of complex problem-solving behaviors in this species including stimulus preexposure and social learning.
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Gosling, S. D. (1998). Personality dimensions in spotted hyenas (Crocuta crocuta). J Comp Psychol, 112(2), 107–118.
Abstract: Personality ratings of 34 spotted hyenas (Crocuta crocuta) were made by 4 observers who knew the animals well. Analyses suggest that (a) hyena personality traits were rated with generally high reliability; (b) 5 broad dimensions (Assertiveness, Excitability, Human-Directed Agreeableness, Sociability, and Curiosity) captured about 75% of the total variance; (c) this dimensional structure could not be explained in terms of dominance status, sex, age, or appearance; and (d) as expected, female hyenas were more assertive than male hyenas. Comparisons with previous research provide evidence for the cross-species generality of Excitability, Sociability, and especially Assertiveness. Discussion focuses on methodological issues in research on animal personality and on the potential contributions this research can make for understanding the biological and environmental bases of personality.
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Miklósi, A., Polgárdi, R., Topál, J., & Csányi, V. (1998). Use of experimenter-given cues in dogs. Anim. Cogn., 1(2), 113–121.
Abstract: Since the observations of O. Pfungst the use of human-provided cues by animals has been well-known in the behavioural sciences (“Clever Hans effect”). It has recently been shown that rhesus monkeys (Macaca mulatta) are unable to use the direction of gazing by the experimenter as a cue for finding food, although after some training they learned to respond to pointing by hand. Direction of gaze is used by chimpanzees, however. Dogs (Canis familiaris) are believed to be sensitive to human gestural communication but their ability has never been formally tested. In three experiments we examined whether dogs can respond to cues given by humans. We found that dogs are able to utilize pointing, bowing, nodding, head-turning and glancing gestures of humans as cues for finding hidden food. Dogs were also able to generalize from one person (owner) to another familiar person (experimenter) in using the same gestures as cues. Baseline trials were run to test the possibility that odour cues alone could be responsible for the dogs' performance. During training individual performance showed limited variability, probably because some dogs already “knew” some of the cues from their earlier experiences with humans. We suggest that the phenomenon of dogs responding to cues given by humans is better analysed as a case of interspecific communication than in terms of discrimination learning.
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