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Sovrano, V., & Bisazza, A. (2008). Recognition of partly occluded objects by fish. Anim. Cogn., 11(1), 1435–9448.
Abstract: Abstract The ability to visually complete partly occluded objects (so-called `“amodal completion”) has been documented in mammals and birds. Here, we report the first evidence of such a perceptual ability in a fish species. Fish (Xenotoca eiseni) were trained to discriminate between a complete and an amputated disk. Thereafter, the fish performed test trials in which hexagonal polygons were either exactly juxtaposed or only placed close to the missing sectors of the disk in order to produce or not produce the impression (to a human observer) of an occlusion of the missing sectors of the disk by the polygon. In another experiment, fish were first trained to discriminate between hexagonal polygons that were either exactly juxtaposed or only placed close to the missing sectors of a disk, and then tested for choice between a complete and an amputated disk. In both experiments, fish behaved as if they were experiencing visual completion of the partly occluded stimuli. These findings suggest that the ability to visually complete partly occluded objects may be widespread among vertebrates, possibly inherited in mammals, birds and fish from early vertebrate ancestors.
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Bräuer, J., Call, J., & Tomasello, M. (2008). Chimpanzees do not take into account what others can hear in a competitive situation. Anim. Cogn., 11(1), 1435–9448.
Abstract: Chimpanzees (Pan troglodytes) know what others can and cannot see in a competitive situation. Does this reflect a general understanding the perceptions of others` In a study by Hare et al. (2000) pairs of chimpanzees competed over two pieces of food. Subordinate individuals preferred to approach food that was behind a barrier that the dominant could not see, suggesting that chimpanzees can take the visual perspective of others. We extended this paradigm to the auditory modality to investigate whether chimpanzees are sensitive to whether a competitor can hear food rewards being hidden. Results suggested that the chimpanzees did not take what the competitor had heard into account, despite being able to locate the hiding place themselves by the noise.
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Krueger, K., & Heinze, J. (2008). Horse sense: social status of horses (Equus caballus) affects their likelihood of copying other horses` behavior. Anim. Cogn., 11(3), 431–439.
Abstract: Animals that live in stable social groups need to gather information on their own relative position in the group`s social hierarchy, either by directly threatening or challenging others, or in a less costly manner, by observing interactions among others. Such indirect inference of dominance relationships has previously been reported from primates, rats, and birds and fish. Here, we show that domestic horses, Equus caballus, are similarly capable of social cognition. Taking advantage of a specific “following behavior” that horses show towards humans in a riding arena, we investigated whether bystander horses adjust their response to an experimenter according to the observed interaction and their own dominance relationship with the horse whose reaction to the experimenter they had observed before. Horses copied the following behavior towards an experimenter after watching a dominant horse following, but did not follow after observing a subordinate horse or a horse from another social group doing so. The following behavior which horses show towards an experimenter therefore appears to be affected by the demonstrator`s behavior and social status relative to the observer.
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Maros, K., Gácsi, M., & Miklósi, Á. (2008). Comprehension of human pointing gestures in horses ( Equus caballus ). Anim. Cogn., 11(3), 457–466.
Abstract: Abstract Twenty domestic horses (Equus caballus) were tested for their ability to rely on different human gesticular cues in a two-way object choice task. An experimenter hid food under one of two bowls and after baiting, indicated the location of the food to the subjects by using one of four different cues. Horses could locate the hidden reward on the basis of the distal dynamic-sustained, proximal momentary and proximal dynamic-sustained pointing gestures but failed to perform above chance level when the experimenter performed a distal momentary pointing gesture. The results revealed that horses could rely spontaneously on those cues that could have a stimulus or local enhancement effect, but the possible comprehension of the distal momentary pointing remained unclear. The results are discussed with reference to the involvement of various factors such as predisposition to read human visual cues, the effect of domestication and extensive social experience and the nature of the gesture used by the experimenter in comparative investigations.
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Mehlis, M., Bakker, T., & Frommen, J. (2008). Smells like sib spirit: kin recognition in three-spined sticklebacks ( Gasterosteus aculeatus ) is mediated by olfactory cues. Anim. Cogn., 11(4), 643–650.
Abstract: Abstract: The ability to recognise kin has been demonstrated in several animal species. However, the mechanisms of kin recognition often remain unknown. The most frequently discussed sensory modalities to recognise kin are visual, olfactory and acoustical cues. Three-spined sticklebacks (Gasterosteus aculeatus) are able to differentiate between kin and non-kin when presented visual and olfactory cues combined. To elucidate, which cues they use to recognise kin female sticklebacks were given the choice between two identical computer animations of courting stickleback males. Next to one animation, water conditioned by a brother was added, while near the other, water from an unrelated male was added. In half of the experiments, the brother was familiar while in the other half he was unfamiliar to the female. Both scenarios were carried out with both outbred and inbred fish. The results showed that the females adjusted their choice behaviour according to relatedness. Furthermore, they were able to recognise both familiar as well as unfamiliar brothers. Inbreeding did not affect this ability. Hence, three-spined sticklebacks are able to recognise their relatives using olfactory cues alone. The cognitive mechanisms underlying this ability were independent from familiarity and not impaired by inbreeding.
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Warren-Smith, A. K., & McGreevy, P. D. (2008). Preliminary investigations into the ethological relevance of round-pen (round-yard) training of horses. Journal of Applied Animal Welfare Science, 11(3), 285–298.
Abstract: Recently, training horses within round-pens has increased in popularity. Practitioners often maintain that the responses they elicit from horses are similar to signals used with senior conspecifics. To audit the responses of horses to conspecifics, 6 mare-young-horse dyads, this study introduced them to each other in a round-pen and videoed them for 8 min. These dyads spent significantly more time farther than 10 m apart than they did less than 1 m apart (p < .001). The time they spent less than 1 m apart decreased over the 8-min test period (p = .018). Mares occupied the center of the round-pen and chased youngsters for 0.73% of the test period (p < .001). Mares made all agonistic approaches (p < .001), and youngsters (p = .018) made all investigative approaches. Head lowering and licking-and-chewing were exhibited most when the youngsters were facing away from the mares (p < .001). The frequency of head lowering increased during the test period (p = .027), whereas the frequency of licking-and-chewing did not change. The results bring into question the popular interpretation and ethological relevance of equine responses commonly described in round-pen training and show that mares did not condition young horses to remain in close proximity to them.
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Goodwin, D., McGreevy, P. D., Heleski, C., Randle, H., & Waran, N. (2008). Equitation science: The application of science in equitation. Journal of Applied Animal Welfare Science, 11(3), 185–190.
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De Cremer, D., & van Dijk, E. (2008). Leader--Follower Effects in Resource Dilemmas: The Roles of Leadership Selection and Social Responsibility. Group Processes Intergroup Relations, 11(3), 355–369.
Abstract: Previous research on the allocation of scarce resources shows that when people are assigned labels of leader or follower in their group, leaders allocate more of the scarce resources to themselves than followers do. In three laboratory studies, we examine the idea that how people are selected for the leader role (i.e. election or appointment) determines whether leaders take more or equal shares (relative to followers) from a common resource. In a first experiment, we show that participants were more accepting of norm violating behavior by an appointed versus elected leader. In a second experiment, we show that when participants were assigned to a leader or follower role, allocations of appointed leaders differed significantly from those of elected leaders and followers, whereas there was no difference between the two latter conditions. Moreover, elected leaders were shown to feel more social responsibility than both appointed leaders and followers. In a final experiment, we show that when participants were primed with the concept of social responsibility (relative to a neutral condition) no difference in allocations between appointed and elected leaders emerged.
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Subiaul, F., Vonk, J., Okamoto-Barth, S., & Barth, J. (2008). Do chimpanzees learn reputation by observation? Evidence from direct and indirect experience with generous and selfish strangers. Anim. Cogn., 11(4), 611–623.
Abstract: Abstract  Can chimpanzees learn the reputation of strangers indirectly by observation? Or are such stable behavioral attributions made exclusively by first-person interactions? To address this question, we let seven chimpanzees observe unfamiliar humans either consistently give (generous donor) or refuse to give (selfish donor) food to a familiar human recipient (Experiments 1 and 2) and a conspecific (Experiment 3). While chimpanzees did not initially prefer to beg for food from the generous donor (Experiment 1), after continued opportunities to observe the same behavioral exchanges, four chimpanzees developed a preference for gesturing to the generous donor (Experiment 2), and transferred this preference to novel unfamiliar donor pairs, significantly preferring to beg from the novel generous donors on the first opportunity to do so. In Experiment 3, four chimpanzees observed novel selfish and generous acts directed toward other chimpanzees by human experimenters. During the first half of testing, three chimpanzees exhibited a preference for the novel generous donor on the first trial. These results demonstrate that chimpanzees can infer the reputation of strangers by eavesdropping on third-party interactions.
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Dacke, M., & Srinivasan, M. (2008). Evidence for counting in insects. Anim. Cogn., 11(4), 683–689.
Abstract: Abstract  Here we investigate the counting ability in honeybees by training them to receive a food reward after they have passed a specific number of landmarks. The distance to the food reward is varied frequently and randomly, whilst keeping the number of intervening landmarks constant. Thus, the bees cannot identify the food reward in terms of its distance from the hive. We find that bees can count up to four objects, when they are encountered sequentially during flight. Furthermore, bees trained in this way are able count novel objects, which they have never previously encountered, thus demonstrating that they are capable of object-independent counting. A further experiment reveals that the counting ability that the bees display in our experiments is primarily sequential in nature. It appears that bees can navigate to food sources by maintaining a running count of prominent landmarks that are passed en route, provided this number does not exceed four.
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