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Guo, K., Meints, K., Hall, C., Hall, S., & Mills, D. (2009). Left gaze bias in humans, rhesus monkeys and domestic dogs. Anim. Cogn., 12(3), 409–418.
Abstract: While viewing faces, human adults often demonstrate a natural gaze bias towards the left visual field, that is, the right side of the viewee’s face is often inspected first and for longer periods. Using a preferential looking paradigm, we demonstrate that this bias is neither uniquely human nor limited to primates, and provide evidence to help elucidate its biological function within a broader social cognitive framework. We observed that 6-month-old infants showed a wider tendency for left gaze preference towards objects and faces of different species and orientation, while in adults the bias appears only towards upright human faces. Rhesus monkeys showed a left gaze bias towards upright human and monkey faces, but not towards inverted faces. Domestic dogs, however, only demonstrated a left gaze bias towards human faces, but not towards monkey or dog faces, nor to inanimate object images. Our findings suggest that face- and species-sensitive gaze asymmetry is more widespread in the animal kingdom than previously recognised, is not constrained by attentional or scanning bias, and could be shaped by experience to develop adaptive behavioural significance.
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Hobaiter, C., & Byrne, R. (2011). Serial gesturing by wild chimpanzees: its nature and function for communication. Anim. Cogn., 14(6), 827–838.
Abstract: Chimpanzees at Budongo, Uganda, regularly gesture in series, including ‘bouts’ of gesturing that include response waiting and ‘sequences’ of rapid-fire gesturing without pauses. We examined the distribution and correlates of 723 sequences and 504 bouts for clues to the function of multigesture series. Gesturing by older chimpanzees was more likely to be successful, but the success rate of any particular gesture did not vary with signaller age. Rather, older individuals were more likely to choose successful gestures, and these highly successful gestures were more often used singly. These patterns explain why bouts were recorded most in younger animals, whereas older chimpanzees relied more on single gestures: bouts are best interpreted as a consequence of persistence in the face of failure. When at least one gesture of a successful type occurred in a sequence, that sequence was more likely to be successful; overall, however, sequences were less successful than single gestures. We suggest that young chimpanzees use sequences as a ‘fail-safe’ strategy: because they have the innate potential to produce a large and redundant repertoire of gestures but lack knowledge of which of them would be most efficient. Using sequences increases the chance of giving one effective gesture and also allows users to learn the most effective types. As they do so, they need to use sequences less; sequences may remain important for subtle interpersonal adjustment, especially in play. This ‘Repertoire Tuning’ hypothesis explains a number of results previously reported from chimpanzee gesturing.
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Slobodchikoff, C., Paseka, A., & Verdolin, J. (2009). Prairie dog alarm calls encode labels about predator colors. Anim. Cogn., 12(3), 435–439.
Abstract: Some animals have the cognitive capacity to differentiate between different species of predators and generate different alarm calls in response. However, the presence of any addition information that might be encoded into alarm calls has been largely unexplored. In the present study, three similar-sized human females walked through a Gunnison’s prairie dog ( Cynomys gunnisoni ) colony wearing each of three different-colored shirts: blue, green, and yellow. We recorded the alarm calls and used discriminant function analysis to assess whether the calls for the different-colored shirts were significantly different. The results showed that the alarm calls for the blue and the yellow shirts were significantly different, but the green shirt calls were not significantly different from the calls for the yellow shirt. The colors that were detected, with corresponding encoding into alarm calls, reflect the visual perceptual abilities of the prairie dogs. This study suggests that prairie dogs are able to incorporate labels about the individual characteristics of predators into their alarm calls, and that the complexity of information contained in animal alarm calls may be greater than has been previously believed.
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Hobaiter, C., & Byrne, R. (2011). The gestural repertoire of the wild chimpanzee. Anim. Cogn., 14(5), 745–767.
Abstract: Great ape gestural communication is known to be intentional, elaborate and flexible; yet there is controversy over the best interpretation of the system and how gestures are acquired, perhaps because most studies have been made in restricted, captive settings. Here, we report the first systematic analysis of gesture in a population of wild chimpanzees. Over 266 days of observation, we recorded 4,397 cases of intentional gesture use in the Sonso community, Budongo, Uganda. We describe 66 distinct gesture types: this estimate appears close to asymptote, and the Sonso repertoire includes most gestures described informally at other sites. Differences in repertoire were noted between individuals and age classes, but in both cases, the measured repertoire size was predicted by the time subjects were observed gesturing. No idiosyncratic usages were found, i.e. no gesture type was used only by one individual. No support was found for the idea that gestures are acquired by ‘ontogenetic ritualization’ from originally effective actions; moreover, in detailed analyses of two gestures, action elements composing the gestures did not closely match those of the presumed original actions. Rather, chimpanzee gestures are species-typical; indeed, many are ‘family-typical’, because gesture types recorded in gorillas, orangutans and chimpanzee overlap extensively, with 24 gestures recorded in all three genera. Nevertheless, chimpanzee gestures are used flexibly across a range of contexts and show clear adjustment to audience (e.g. silent gestures for attentive targets, contact gestures for inattentive ones). Such highly intentional use of a species-typical repertoire raises intriguing questions for the evolution of advanced communication.
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MacLean, E., Matthews, L., Hare, B., Nunn, C., Anderson, R., Aureli, F., et al. (2012). How does cognition evolve? Phylogenetic comparative psychology. Anim. Cogn., 15(2), 223–238.
Abstract: Now more than ever animal studies have the potential to test hypotheses regarding how cognition evolves. Comparative psychologists have developed new techniques to probe the cognitive mechanisms underlying animal behavior, and they have become increasingly skillful at adapting methodologies to test multiple species. Meanwhile, evolutionary biologists have generated quantitative approaches to investigate the phylogenetic distribution and function of phenotypic traits, including cognition. In particular, phylogenetic methods can quantitatively (1) test whether specific cognitive abilities are correlated with life history (e.g., lifespan), morphology (e.g., brain size), or socio-ecological variables (e.g., social system), (2) measure how strongly phylogenetic relatedness predicts the distribution of cognitive skills across species, and (3) estimate the ancestral state of a given cognitive trait using measures of cognitive performance from extant species. Phylogenetic methods can also be used to guide the selection of species comparisons that offer the strongest tests of a priori predictions of cognitive evolutionary hypotheses (i.e., phylogenetic targeting). Here, we explain how an integration of comparative psychology and evolutionary biology will answer a host of questions regarding the phylogenetic distribution and history of cognitive traits, as well as the evolutionary processes that drove their evolution.
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Kaminski, G., Gentaz, E., & Mazens, K. (2012). Development of children’s ability to detect kinship through facial resemblance. Anim. Cogn., 15(3), 421–427.
Abstract: Facial features appear to be a prominent kinship cue for ascribing relatedness among human individuals. Although there is evidence that adults can detect kinship in unrelated and unfamiliar individual’s faces, it remains to be seen whether people already possess the ability when they are young. To further understand the development of this skill, we explored children’s ability to detect parent-offspring resemblance in unrelated and unfamiliar faces. To this end, we tested approximately 140 children, aged 5–11, in two photo-matching tasks. We used a procedure that asked them to match one neonate’s face to one of three adults’ faces (Task 1), or to match one adult’s face to one of three neonate’s faces (Task 2). Our findings reveal asymmetrical performance, depending on the tasks assigned (performance of Task 2 is stronger than for Task 1), and on the sex of individuals who made up the parent-offspring pair (male parents are better matched with neonates than female parents, and boys are better matched than girls). The picture that emerges from our study is, on one hand, that the ability to detect kinship is already present at the age of five but continues to improve as one gets older, and on the other, that perception of parent-offspring facial resemblance varies according to the appraisers’ characteristics.
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Meyer, S., Nürnberg, G., Puppe, B., & Langbein, J. (2012). The cognitive capabilities of farm animals: categorisation learning in dwarf goats (Capra hircus). Anim. Cogn., 15(4), 567–576.
Abstract: The ability to establish categories enables organisms to classify stimuli, objects and events by assessing perceptual, associative or rational similarities and provides the basis for higher cognitive processing. The cognitive capabilities of farm animals are receiving increasing attention in applied ethology, a development driven primarily by scientifically based efforts to improve animal welfare. The present study investigated the learning of perceptual categories in Nigerian dwarf goats ( Capra hircus ) by using an automated learning device installed in the animals’ pen. Thirteen group-housed goats were trained in a closed-economy approach to discriminate artificial two-dimensional symbols presented in a four-choice design. The symbols belonged to two categories: category I, black symbols with an open centre (rewarded) and category II, the same symbols but filled black (unrewarded). One symbol from category I and three different symbols from category II were used to define a discrimination problem. After the training of eight problems, the animals were presented with a transfer series containing the training problems interspersed with completely new problems made from new symbols belonging to the same categories. The results clearly demonstrate that dwarf goats are able to form categories based on similarities in the visual appearance of artificial symbols and to generalise across new symbols. However, the goats had difficulties in discriminating specific symbols. It is probable that perceptual problems caused these difficulties. Nevertheless, the present study suggests that goats housed under farming conditions have well-developed cognitive abilities, including learning of open-ended categories. This result could prove beneficial by facilitating animals’ adaptation to housing environments that favour their cognitive capabilities.
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Verdolin, J. (2009). Gunnison’s prairie dog (Cynomys gunnisoni): testing the resource dispersion hypothesis. Beh. Ecol. Sociobiol., 63(6), 789–799.
Abstract: Few studies have experimentally tested the resource dispersion hypothesis (RDH). In this study, I tested whether space use and social organization of Gunnison’s prairie dog responded to changes in the dispersion and abundance of resources. Food manipulations were carried out during the reproductive and nonreproductive seasons across 2 years. Gunnison’s prairie dog adults responded to the experiments by decreasing territory size as food became patchier in space and time. Both males and females modified their home ranges, with no detectable difference between sexes, either prior to or during the experiments. As food became patchier in space and time, the spatial overlap of adults increased, whereas it decreased as food became more evenly dispersed. The average size of a group, defined as those individuals occupying the same territory, did not change significantly as a result of the experiments. Where changes in the composition and size of groups did occur, there was no indication that such changes were sex specific. Results from this study support critical components of the RDH and strongly suggest that patterns of space use and social structure in Gunnison’s prairie dogs are the result of individual responses to resource abundance and distribution.
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Eagle, N., & Pentland, A. (2009). Eigenbehaviors: identifying structure in routine. Behav. Ecol. Sociobiol., 63(7), 1057-1066.
Abstract: Longitudinal behavioral data generally contains a significant amount of structure. In this work, we identify the structure inherent in daily behavior with models that can accurately analyze, predict, and cluster multimodal data from individuals and communities within the social network of a population. We represent this behavioral structure by the principal components of the complete behavioral dataset, a set of characteristic vectors we have termed eigenbehaviors. In our model, an individual’s behavior over a specific day can be approximated by a weighted sum of his or her primary eigenbehaviors. When these weights are calculated halfway through a day, they can be used to predict the day’s remaining behaviors with 79% accuracy for our test subjects. Additionally, we demonstrate the potential for this dimensionality reduction technique to infer community affiliations within the subjects’ social network by clustering individuals into a behavior space spanned by a set of their aggregate eigenbehaviors. These behavior spaces make it possible to determine the behavioral similarity between both individuals and groups, enabling 96% classification accuracy of community affiliations within the population-level social network. Additionally, the distance between individuals in the behavior space can be used as an estimate for relational ties such as friendship, suggesting strong behavioral homophily amongst the subjects. This approach capitalizes on the large amount of rich data previously captured during the Reality Mining study from mobile phones continuously logging location, proximate phones, and communication of 100 subjects at MIT over the course of 9 months. As wearable sensors continue to generate these types of rich, longitudinal datasets, dimensionality reduction techniques such as eigenbehaviors will play an increasingly important role in behavioral research.
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Fischhoff, I., Dushoff, J., Sundaresan, S., Cordingley, J., & Rubenstein, D. (2009). Reproductive status influences group size and persistence of bonds in male plains zebra (Equus burchelli). Behav. Ecol. Sociobiol., 63(7), 1035-1043.
Abstract: Animal groups arise from individuals’ choices about the number, characteristics, and identity of associates. Individuals make these choices to gain benefits from their associations. As the needs of an individual change with its phenotype, so too we expect the nature of its associations to vary. In this paper, we investigate how the social priorities of male plains zebra (Equus burchelli) depend on reproductive state. An adult male is either a bachelor, and lacking mating access, or a stallion defending a harem. Multiple harems and bachelor males aggregate in larger herds. Herds frequently split and merge, affording males opportunities to change associates. Over a 4-year period, we sampled the herd associations in a population of 500–700 zebras. To isolate the effects of reproductive state on male social behavior, we account for potential confounding factors: changes in population size, grouping tendencies, and sampling intensity. We develop a generally applicable permutation procedure, which allows us to test the null hypothesis that social behavior is independent of male status. Averaging over all individuals in the population, we find that a typical bachelor is found in herds containing significantly more adults, bachelors, and stallions than the herds of a typical stallion. Further, bachelors’ bonds with each other are more persistent over time than those among stallions. These results suggest that bachelors form cohesive cliques, in which we may expect cooperative behaviors to develop. Stallion–stallion associations are more diffuse, and less conducive to long-term cooperation.
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