Soproni, K., Miklósi, A., Topál, J., & Csányi, V. (2001). Comprehension of human communicative signs in pet dogs (Canis familiaris). J Comp Psychol, 115(2), 122–126.
Abstract: On the basis of a study by D. J. Povinelli, D. T. Bierschwale, and C. G. Cech (1999), the performance of family dogs (Canis familiaris) was examined in a 2-way food choice task in which 4 types of directional cues were given by the experimenter: pointing and gazing, head-nodding (“at target”), head turning above the correct container (“above target”), and glancing only (“eyes only”). The results showed that the performance of the dogs resembled more closely that of the children in D. J. Povinelli et al.'s study, in contrast to the chimpanzees' performance in the same study. It seems that dogs, like children, interpret the test situation as being a form of communication. The hypothesis is that this similarity is attributable to the social experience and acquired social routines in dogs because they spend more time in close contact with humans than apes do, and as a result dogs are probably more experienced in the recognition of human gestures.
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Sousa, C., & Matsuzawa, T. (2001). The use of tokens as rewards and tools by chimpanzees (Pan troglodytes). Anim. Cogn., 4(3), 213–221.
Abstract: This paper explores the effectiveness of token rewards in maintaining chimpanzees ( Pan troglodytes) in working at intellectually costly tasks, and studies the “saving” behavior of the subjects, investigating the factors that can condition it. Two experiments were run. Tokens were introduced as rewards in a matching-to-sample task and used as exchange tools for food by three adult female chimpanzees. Subjects' performances were maintained at constant high levels of accuracy, suggesting that the tokens were almost equivalent to direct food rewards. The results also showed the emergence of saving behavior. The subjects spontaneously saved the tokens during the matching-to-sample task before exchanging them for food. The chimpanzees also learned a new symbolic discrimination task, with tokens as the reward. During this learning process a rarely reported phenomenon emerged: one of the subjects showed symmetry, a form of stimulus equivalence.
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Spengler M.I., & Rasia M. (2001). Influence of Plasma Proteins on Erythrocyte Aggregation in Three Mammalian Species. Vet.Res.Comm, 25(7), 591–599.
Abstract: The aggregation capacity of human erythrocytes lies between that of the non-aggregating bovine erythrocytes and the remarkably aggregating equine ones. As the ability to aggregate is attributed to cell factors and the composition of the plasma proteins, the role that plasma proteins play in the aggregation process in these three species was studied. Washed erythrocytes were suspended in phosphate-buffered saline (PBS; pH 7.4, 300 mOsm/L) plus polyvinylpyrrolidone (PVP) in a suitable concentration to obtain an average intensity of aggregation (control media). The superimposed effect of replacing 80% of the medium by either autologous plasma, serum or albumin solution was studied. The plasma proteins appeared to enhance aggregation by human and equine erythrocytes, but impaired this process in bovine erythrocytes. Some evidence was obtained supporting the existence of serum factors capable of reducing aggregation of erythrocytes in cattle and it was concluded that the non-aggregating behaviour of bovine erythrocytes may be due to the cells interacting particularly with the macromolecules in the serum.
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Stahl, J., Tolsma, P. H., Loonen, M. J. J. E., & Drent, R. H. (2001). Subordinates explore but dominants profit: resource competition in high Arctic barnacle goose flocks.61(1), 257–264.
Abstract: Social dominance plays an important role in assessing and obtaining access to patchy or scarce food sources in group-foraging herbivores. We investigated the foraging strategies of individuals with respect to their social position in the group in a flock of nonbreeding, moulting barnacle geese, Branta leucopsis, on high Arctic Spitsbergen. We first determined the dominance rank of individually marked birds. The dominance of an individual was best described by its age and its sex-specific body mass. Mating status explained the large variation in dominance among younger birds, as unpaired yearlings ranked lowest. In an artificially created, competitive situation, subordinate individuals occupied explorative front positions in the flock and were the first to find sites with experimentally enriched vegetation. Nevertheless, they were displaced quickly from these favourable sites by more dominant geese which were able to monopolize them. The enhanced sites were subsequently visited preferentially by individuals that succeeded in feeding there when the exclosures were first opened. Data on walking speed of foraging individuals and nearest-neighbour distances in the group suggest that subordinates try to compensate for a lower energy intake by exploring and by lengthening the foraging bout. Observations of our focal birds during the following breeding season revealed that females that returned to the study area were significantly more dominant in the previous year than those not seen in the area again.
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Stoinski, T. S., Wrate, J. L., Ure, N., & Whiten, A. (2001). Imitative learning by captive western lowland gorillas (Gorilla gorilla gorilla) in a simulated food-processing task. J Comp Psychol, 115(3), 272–281.
Abstract: Although field studies have suggested the existence of cultural transmission of foraging techniques in primates, identification of transmission mechanisms has remained elusive. To test experimentally for evidence of imitation in the current study, we exposed gorillas (Gorilla gorilla gorilla) to an artificial fruit foraging task designed by A. Whiten and D. M. Custance (1996). Gorillas (n=6) watched a human model remove a series of 3 defenses around a fruit. Each of the defenses was removed using 1 of 2 alternative techniques. Subsequent video analysis of gorillas' behavior showed a significant tendency to copy the observed technique on 1 of the individual defenses and the direction of removal on another defense. This is the first statistically reliable evidence of imitation in gorillas. Sequence of defense removal was not replicated. The gorillas' responses were most similar to those of chimpanzees.
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Stokes, E., & Byrne, R. (2001). Cognitive capacities for behavioural flexibility in wild chimpanzees (Pan troglodytes): the effect of snare injury on complex manual food processing. Anim. Cogn., 4(1), 11–28.
Abstract: In chimpanzees, it is only in the restricted context of tool use that manual and cognitive skills have been described, comparable to those that gorillas and orang-utans display in obtaining plant foods. We report the complex food preparation skills used to eat, without tools, the leaves of the tree Broussonettia papyrifera in the Sonso community of chimpanzees at Budongo Forest, Uganda. Able-bodied individuals used multi-stage techniques that required bimanual role differentiation at several stages, and were hierarchical in organisation. A total repertoire of 14 techniques was found, with strong preference in all individuals for either of two of these; 6 additional techniques were found when flowers and leaves were eaten together. However, in this community over 20% of individuals suffer from some form of upper- or lower-limb injury as a result of snares. We investigated the manner of compensation for upper-limb injury. Only the most severely injured showed reduced feeding efficiency. Injured individuals were found to use the same repertoire of techniques as able-bodied chimpanzees. We found no evidence to suggest that injured individuals were able to develop wholly novel techniques optimal for their specific injuries, although shifts in preference for particular techniques did occur. Rather, injured individuals used novel ways of achieving particular steps in the process; by “working around” their impairments; in this way, they managed to use the same techniques as the able-bodied. Since snare injuries generally befall young animals, these results suggest that chimpanzees learn techniques partly through observational learning (of, necessarily, able-bodied individuals).
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Takeshita, H. (2001). Development of combinatory manipulation in chimpanzee infants (Pan troglodytes). Anim. Cogn., 4(3), 335–345.
Abstract: I made systematic observations of three infant chimpanzees aged 2–4 years, who participated in a series of diagnostic tests of combinatory manipulation. The tasks were stacking blocks, seriating nesting cups, and inserting an object into the corresponding hole in a plate or a box. These tasks were originally devised for developmental diagnosis of human infants. The chimpanzee infants displayed combinatory manipulation comparable to that of 1-year-old human infants. Common motor characteristics were observed across the tasks, namely “repetition” of actions, “adjustment” of actions, “reversal” of actions, and “shifts” of attention. Humans and chimpanzees share these actions when manipulating multiple objects to complete a task. Repetition, adjustment, and reversal of actions and shifts of attention underlie higher levels of cognition common to both species.
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Tanaka, M. (2001). Discrimination and categorization of photographs of natural objects by chimpanzees (Pan troglodytes). Anim. Cogn., 4(3), 201–211.
Abstract: Two experiments assessed the ability of four adult female chimpanzees to categorize natural objects. Chimpanzees were initially trained to match different color photographs of familiar objects from four possible categories. In training, all the comparison stimuli were from the same category in one condition, and from different categories in another condition. For all subjects, training performance was consistently better for the “different category” than for the “same category” trials. Probe trials were shown after training. In probe trials, the sample and positive comparison stimuli were different items from the same category, and the foils were selected from among the three other test categories. Individual performance was above chance in probe trials, suggesting that categorization by chimpanzees may transcend perceptual resemblance. These results were later replicated with novel stimulus items from the same four categories (experiment 2). Altogether, this research demonstrates that chimpanzees grouped perceptually different exemplars within the same category, and further suggests that these animals formed conceptual representations of the categories.
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Taylor, J. G. (2001). What do Neuronal Network Models of the Mind Indicate about Animal Consciousness? Animal Welfare, 10, 63–75.
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Tebbich, S., Taborsky, M., Fessl, B., & Blomqvist, D. (2001). Do woodpecker finches acquire tool-use by social learning? Proc. Roy. Soc. Lond. B Biol. Sci., 268(1482), 2189–2193.
Abstract: Tool–use is widespread among animals, but except in primates the development of this behaviour is poorly known. Here, we report on the first experimental study to our knowledge of the mechanisms underlying the acquisition of tool–use in a bird species. The woodpecker finch Cactospiza pallida, endemic to the Galápagos Islands, is a famous textbook example of tool–use in animals. This species uses modified twigs or cactus spines to pry arthropods out of tree holes. Using nestlings and adult birds from the field, we tested experimentally whether woodpecker finches learn tool–use socially. We show that social learning is not essential for the development of tool–use: all juveniles developed tool–use regardless of whether or not they had a tool–using model. However, we found that not all adult woodpecker finches used tools in our experiments. These non–tool–using individuals also did not learn this task by observing tool–using conspecifics. Our results suggest that tool–use behaviour depends on a very specific learning disposition that involves trial–and–error learning during a sensitive phase early in ontogeny.
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