Regolin, L., Tommasi, L., & Vallortigara, G. (2000). Visual perception of biological motion in newly hatched chicks as revealed by an imprinting procedure. Anim. Cogn., 3(1), 53–60.
Abstract: Day-old chicks were exposed to point-light animation sequences depicting either a walking hen or a rotating cylinder. On a subsequent free-choice test (experiment 1) the chicks approached the novel stimulus, irrespective of this being the hen or the cylinder. In order to obtain equivalent local motion vectors, in experiments 2 and 3 newly hatched chicks were exposed either to a point-light animation sequence depicting a walking hen, or to a positionally scrambled walking hen (i.e. an animation in which exactly the same set of dots in motion as that employed for the walking hen was presented, but with spatially randomized starting positions). Chicks tested on day 1 (experiment 2) or on day 2 (i.e. after a period in the dark following exposure on day 1 (experiment 3)) proved able to discriminate the two animation sequences: males preferentially approached the novel stimulus, females the familiar one. These results indicate that discrimination was not based on local motion vectors, but rather on the temporally integrated motion sequence.
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Kusayama, T., Bischof, H. - J., & Watanabe, S. (2000). Responses to mirror-image stimulation in jungle crows (Corvus macrorhynchos). Anim. Cogn., 3(1), 61–64.
Abstract: Four jungle crows (Corvus macrorhynchos) were exposed to a mirror placed either vertically or horizontally. The most frequently observed behaviors were pecking at the mirror and wing flapping when looking toward the mirror. These behavior patterns, which were only rarely observed when the mirror was reversed, can be interpreted as aggressive behaviors against a conspecific. The vertical mirror evoked the behaviors more often than the horizontal mirror. The present results suggest that crows perceive their mirror image as an image of a conspecific, not as their own.
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Waite, T. A., & Field, K. L. (2000). Erroneous choice and foregone gains in hoarding gray jays (Perisoreus canadensis). Anim. Cogn., 3(3), 127–134.
Abstract: Under the conventional assumption that natural selection favors choice behavior that maximizes some fitness-related currency, a forager making repeated binary choices should consistently choose the more valuable option. Under the alternative assumption that natural selection favors choice behavior that minimizes costly errors, erroneous choice is not only expected but is expected to be common when the cost of errors is low. This cost depends on the potential rate of return: the higher this rate, the smaller the cost of choosing the less valuable option. When this rate is very high, a forager may err frequently and yet forego no appreciable fitness gain. Errors should thus be more common when interruptions to foraging are shorter. Our experimental results supported this prediction: gray jays chose the less valuable option more frequently when subjected to shorter interruptions (experimentally imposed delays to access to food rewards). This tendency is consistent with the idea that an adaptive decision-making process may routinely produce errors, not because errors are in some way adaptive but because their fitness cost is minimal, particularly when delays are short. From a proximate perspective, this tendency to commit errors more frequently following shorter delays may be due to constraints on the jays' information-processing capacity. In general, choice behavior should be viewed as the joint byproduct of adaptive decision making and cognitive constraints.
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von Fersen, L., & Delius, J. D. (2000). Acquired equivalences between auditory stimuli in dolphins (Tursiops truncatus). Anim. Cogn., 3(2), 79–83.
Abstract: This study investigated whether dolphins would show evidence of equivalence class formation between auditory stimuli. Bottlenose dolphins were trained to press one or other of two response levers depending on which one of four auditory stimuli had been previously presented. Once they had learned the initial discriminations, the stimulus-lever contingencies was repeatedly reversed. Within any given session, however, pressing of one lever always led to reward with one set of two tones and pressing the other lever led to non-reward with an alternative set of two tones. After sufficient experience with this response reversal procedure, the dolphins spontaneously chose the same levers they had first learned to be correct with one of the across-set stimulus pairs when later in the session they were presented with the other of the across-set stimulus pairs. They thus demonstrated that they had associated the tones belonging to the two sets within two separate functional classes. It is discussed why the dolphins succeeded with auditory stimuli when they had previously failed in a similar task with visual stimuli.
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Tomonaga, M., & Matsuzawa, T. (2000). Sequential responding to arabic numerals with wild cards by the chimpanzee (Pan troglodytes). Anim. Cogn., 3(1), 1–11.
Abstract: One adult female chimpanzee (Pan troglodytes) was trained to respond serially to three arabic numerals between 1 and 9, presented on a cathode-ray-tube (CRT) screen. To examine the factors affecting her sequential responding behavior, wild-card items were added to the three-item sequences. When this wild-card item remained until the subject responded to the last numeral (i.e., the terminator condition), her response to the terminator at each point of the sequence was controlled by the ordinal distance between numerals. Thus, the number of responses to the terminator increased as the ordinal distance between numerals increased. When the wild-card item was eliminated by the subject's response (wild-card conditions), the probability of responses to the wild card before the first numeral increased as a function of the serial position of the first numeral. These results were consistent with previous studies of response time and suggest both serial position and symbolic distance effects. It is suggested that the subject might form the integrated 9-item linear representations by training of possible subsets of three-item sequences. Knowledge concerning the ordinal position of each numeral was established through this training.
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Ronald J. Schusterman, Colleen J. Reichmuth, & David Kastak. (2000). How Animals Classify Friends and Foes. Curr. Dir. Psychol. Sci., 9, 1–6.
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Guth S., & Guth W. (2000). Morality based on cognition in primates. Journal of Consciousness Studies, 7, 43–46.
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Buchner, H. H. F., Obermuller, S., & Scheidl, M. (2000). Body Centre of Mass Movement in the Sound Horse. The Veterinary Journal, 160(3), 225–234.
Abstract: The body centre of mass (BCM) is a key factor in the analysis of equine locomotion, as its position and movement determines the distribution and magnitude of loads on the limbs. In this study, the three-dimensional (3D) movement of the BCM in walking and trotting horses was assessed using a kinematic, segmental method. Thirty markers representing 20 body segments were recorded in 12 sound horses while standing, walking and trotting on a treadmill using a high-speed video system. Based on segmental inertial data, 3D positions of the segmental centres of mass as well as the total BCM were calculated. The position within the trunk during square standing and the movements of the BCM were determined for the three planes. The position of the BCM in the standing horse is presented relative to external reference points. At the trot, vertical displacement amplitude of the BCM amounted to 53 (6) mm as mean (sd), which was 27% smaller than external trunk movement. Medio-lateral displacement amplitude of the BCM was 19 (4) mm, 34% less than trunk amplitude. Sagittal forward-backward oscillations of the BCM independent from general forward movement were 13 (3) mm, being 24% less than trunk movements. At the walk, vertical, medio-lateral and sagittal BCM movements were smaller than trunk movements by 43, 65 and 65% respectively. The results show reduced and efficient BCM movements compared to the trunk and form a basis for the assessment of various clinical conditions such as lameness, the influence of a rider and various dressage performances.
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Riede, T., Herzel, H., Mehwald, D., Seidner, W., Trumler, E., & Böhme, G. (2000). Nonlinear phenomena in the natural howling of a dog-wolf mix. J Acoust Soc Am, 108.
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Nicol, C. J. (2000). Equine Stereotypies. In: Houpt K.A. (Ed.),. In Recent Advances in Companion Animal Behavior Problems. International Veterinary Information Service.
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