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Author Sovrano, V.; Bisazza, A. url  doi
openurl 
  Title Recognition of partly occluded objects by fish Type Journal Article
  Year 2008 Publication Animal Cognition Abbreviated Journal Anim. Cogn.  
  Volume 11 Issue 1 Pages 1435-9448  
  Keywords Visual completion – Amodal completion – Occlusion – Visual recognition – Fish  
  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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  Call Number Admin @ knut @ Serial 4217  
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Author Bräuer, J.; Call, J.; Tomasello, M. url  doi
openurl 
  Title Chimpanzees do not take into account what others can hear in a competitive situation Type Journal Article
  Year 2008 Publication Animal Cognition Abbreviated Journal Anim. Cogn.  
  Volume 11 Issue 1 Pages 1435-9448  
  Keywords Social cognition – Food competition – Perspective taking  
  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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  Notes Approved no  
  Call Number Admin @ knut @ Serial 4218  
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Author Hattori, Y.; Kuroshima, H.; Fujita, K. url  doi
openurl 
  Title I know you are not looking at me: capuchin monkeys` ? (Cebus apella) sensitivity to human attentional states Type Journal Article
  Year 2007 Publication Animal Cognition Abbreviated Journal Anim. Cogn.  
  Volume 10 Issue 2 Pages 141-148  
  Keywords Capuchin monkeys – Attentional state – Gaze – Social cognition  
  Abstract Abstract  The present study asked whether capuchin monkeys recognize human attentional states. The monkeys requested food from the experimenter by extending an arm (pointing) toward the baited one of two transparent cups. On regular trials the experimenter gave the food immediately to the monkeys upon pointing but on randomly inserted test trials she ignored the pointing for 5 s during which she displayed different attentional states. The monkeys looked at the experimenter's face longer when she looked at the monkeys than when she looked at the ceiling in Experiment 1, and longer when she oriented her head midway between the two cups with eyes open than when she did so with eyes closed in Experiment 2. However, the monkeys showed no differential pointing in these conditions. These results suggest that capuchins are sensitive to eye direction but this sensitivity does not lead to differential pointing trained in laboratory experiments. Furthermore, to our knowledge, this is the first firm behavioral evidence that non-human primates attend to the subtle states of eyes in a food requesting task.  
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  Notes Approved no  
  Call Number Admin @ knut @ Serial 4219  
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Author Voelkl, B.; Huber, L. url  doi
openurl 
  Title Common marmosets (Callithrix jacchus) do not utilize social information in three simultaneous social foraging tasks Type Journal Article
  Year 2007 Publication Animal Cognition Abbreviated Journal Anim. Cogn.  
  Volume 10 Issue 2 Pages 149-158  
  Keywords Marmosets – Social foraging – Social information – Food competition  
  Abstract Abstract  Social foraging is suggested to increase foraging efficiency, as individuals might benefit from public information acquired by monitoring the foraging activities of other group members. We conducted a series experiments with captive common marmosets (Callithrix jacchus) to investigate to what extent marmosets utilize social information about food location when foraging simultaneously with conspecifics. Subjects were confronted with dominant and subordinate demonstrators in three experiments which differed in the amount of information about food location available to the demonstrators. In all three experiments, the focal subjects` performance in the social condition was not enhanced in comparison to a non-social control condition. Because we could rule out kleptoparasitism and aggressive displacements as explanations, we argue that the subjects tendency for scramble competition by avoiding others and dispersing over the foraging area seems to inhibit or mask the acquisition of social information about the location of rewarded patches.  
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  Notes Approved no  
  Call Number Admin @ knut @ Serial 4220  
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Author Bryson, J.; Leong, J. url  doi
openurl 
  Title Primate errors in transitive inference: a two-tier learning model Type Journal Article
  Year 2007 Publication Animal Cognition Abbreviated Journal Anim. Cogn.  
  Volume 10 Issue 1 Pages 1-15  
  Keywords Transitive inference, choice or performance – Task learning – Hippocampal learning – Modelling  
  Abstract Abstract  Transitive performance (TP) is a learning-based behaviour exhibited by a wide range of species, where if a subject has been taught to prefer A when presented with the pair AB but to prefer B when presented with the pair BC, then the subject will also prefer A when presented with the novel pair AC. Most explanations of TP assume that subjects recognize and learn an underlying sequence from observing the training pairs. However, data from squirrel monkeys (Saimiri sciureus) and young children contradict this, showing that when three different items (a triad) are drawn from the sequence, subjects`` performance degrades systematically (McGonigle and Chalmers, Nature 267:694-696, 1977; Chalmers and McGonigle, Journal of Experimental Child Psychology 37:355-377, 1984; Harris and McGonigle, The Quarterly Journal of Experimental Psychology 47B:319-348, 1994). We present here the two-tier model, the first learning model of TP which accounts for this systematic performance degradation. Our model assumes primate TP is based on a general-purpose task learning system rather than a special-purpose sequence-learning system. It supports the hypothesis of Heckers et al. (Hippocampus 14:153-162, 2004) that TP is an expression of two separate general learning elements: one for associating actions and contexts, another for prioritising associations when more than one context is present. The two-tier model also provides explanations for why phased training is important for helping subjects learn the initial training pairs and why some subjects fail to do so. It also supports the Harris and McGonigle (The Quarterly Journal of Experimental Psychology 47B:319-348, 1994) explanation of why, once the training pairs have been acquired, subjects perform transitive choice automatically on two-item diads, but not when exposed to triads from the same sequence.  
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  Notes Approved no  
  Call Number Admin @ knut @ Serial 4221  
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Author Adachi, I.; Kuwahata, H.; Fujita, K. url  doi
openurl 
  Title Dogs recall their owner's face upon hearing the owner's voice Type Journal Article
  Year 2007 Publication Animal Cognition Abbreviated Journal Anim. Cogn.  
  Volume 10 Issue 1 Pages 17-21  
  Keywords Cross-modal representation – Natural concepts – Dogs  
  Abstract Abstract  We tested whether dogs have a cross-modal representation of human individuals. We presented domestic dogs with a photo of either the owner's or a stranger's face on the LCD monitor after playing back a voice of one of those persons. A voice and a face matched in half of the trials (Congruent condition) and mismatched in the other half (Incongruent condition). If our subjects activate visual images of the voice, their expectation would be contradicted in Incongruent condition. It would result in the subjects` longer looking times in Incongruent condition than in Congruent condition. Our subject dogs looked longer at the visual stimulus in Incongruent condition than in Congruent condition. This suggests that dogs actively generate their internal representation of the owner's face when they hear the owner calling them. This is the first demonstration that nonhuman animals do not merely associate auditory and visual stimuli but also actively generate a visual image from auditory information. Furthermore, our subject also looked at the visual stimulus longer in Incongruent condition in which the owner's face followed an unfamiliar person's voice than in Congruent condition in which the owner's face followed the owner's voice. Generating a particular visual image in response to an unfamiliar voice should be difficult, and any expected images from the voice ought to be more obscure or less well defined than that of the owners. However, our subjects looked longer at the owner's face in Incongruent condition than in Congruent condition. This may indicate that dogs may have predicted that it should not be the owner when they heard the unfamiliar person's voice.  
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  Notes Approved no  
  Call Number Admin @ knut @ Serial 4222  
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Author Leaver, L.; Hopewell, L.; Caldwell, C.; Mallarky, L. url  doi
openurl 
  Title Audience effects on food caching in grey squirrels (Sciurus carolinensis): evidence for pilferage avoidance strategies Type Journal Article
  Year 2007 Publication Animal Cognition Abbreviated Journal Anim. Cogn.  
  Volume 10 Issue 1 Pages 23-27  
  Keywords Caching – Deception – Pilferage – Grey squirrels – Sciurus carolinensis  
  Abstract Abstract  If food pilferage has been a reliable selection pressure on food caching animals, those animals should have evolved the ability to protect their caches from pilferers. Evidence that animals protect their caches would support the argument that pilferage has been an important adaptive challenge. We observed naturally caching Eastern grey squirrels (Sciurus carolinensis) in order to determine whether they used any evasive tactics in order to deter conspecific and heterospecific pilferage. We found that grey squirrels used evasive tactics when they had a conspecific audience, but not when they had a heterospecific (corvid) audience. When other squirrels were present, grey squirrels spaced their caches farther apart and preferentially cached when oriented with their backs to other squirrels, but no such effect was found when birds were present. Our data provide the first evidence that caching mammals are sensitive to the risk of pilferage posed by an audience of conspecifics, and that they utilise evasive tactics that should help to minimise cache loss. We discuss our results in relation to recent theory of reciprocal pilferage and compare them to behaviours shown by caching birds.  
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  Notes Approved no  
  Call Number Admin @ knut @ Serial 4223  
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Author Krueger, K.; Heinze, J. url  doi
openurl 
  Title Horse sense: social status of horses (Equus caballus) affects their likelihood of copying other horses` behavior Type Journal Article
  Year 2008 Publication Animal Cognition Abbreviated Journal Anim. Cogn.  
  Volume 11 Issue 3 Pages 431-439  
  Keywords copying, horse, social cognition, sociality  
  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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  Notes Approved no  
  Call Number Equine Behaviour @ team @ Serial 4324  
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Author Maros, K.; Gácsi, M.; Miklósi, Á doi  openurl
  Title Comprehension of human pointing gestures in horses ( Equus caballus ) Type Journal Article
  Year 2008 Publication Animal Cognition Abbreviated Journal Anim. Cogn.  
  Volume 11 Issue 3 Pages 457-466  
  Keywords Human-animal communication – Pointing – Horse  
  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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  Notes Approved no  
  Call Number Equine Behaviour @ team @ Serial 4388  
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Author Sato, W.; Aoki, S. url  doi
openurl 
  Title Right hemispheric dominance in processing of unconscious negative emotion Type Journal Article
  Year 2006 Publication Brain and Cognition Abbreviated Journal  
  Volume 62 Issue 3 Pages 261-266  
  Keywords Right hemispheric dominance; Unconscious negative emotion; Subliminal affective priming; Emotional facial expressions  
  Abstract Right hemispheric dominance in unconscious emotional processing has been suggested, but remains controversial. This issue was investigated using the subliminal affective priming paradigm combined with unilateral visual presentation in 40 normal subjects. In either left or right visual fields, angry facial expressions, happy facial expressions, or plain gray images were briefly presented as negative, positive, and control primes, followed by a mosaic mask. Then nonsense target ideographs were presented, and the subjects evaluated their partiality toward the targets. When the stimuli were presented in the left, but not the right, visual fields, the negative primes reduced the subjects' liking for the targets, relative to the case of the positive or control primes. These results provided behavioral evidence supporting the hypothesis that the right hemisphere is dominant for unconscious negative emotional processing.  
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  Notes Approved no  
  Call Number Equine Behaviour @ team @ Serial 4638  
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