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A. Lanata, A. Guidi, G. Valenza, P. Baragli, & E. P. Scilingo. (2016). Quantitative heartbeat coupling measures in human-horse interaction. In 2016 38th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) (pp. 2696–2699). 2016 38th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (E.
Abstract: Abstract— We present a study focused on a quantitative estimation of a human-horse dynamic interaction. A set of measures based on magnitude and phase coupling between heartbeat dynamics of both humans and horses in three different conditions is reported: no interaction, visual/olfactory interaction and grooming. Specifically, Magnitude Squared Coherence (MSC), Mean Phase Coherence (MPC) and Dynamic Time Warping (DTW) have been used as estimators of the amount of coupling between human and horse through the analysis of their heart rate variability (HRV) time series in a group of eleven human subjects, and one horse. The rationale behind this study is that the interaction of two complex biological systems go towards a coupling process whose dynamical evolution is modulated by the kind and time duration of the interaction itself. We achieved a congruent and consistent
statistical significant difference for all of the three indices. Moreover, a Nearest Mean Classifier was able to recognize the three classes of interaction with an accuracy greater than 70%. Although preliminary, these encouraging results allow a discrimination of three distinct phases in a real human-animal interaction opening to the characterization of the empirically proven relationship between human and horse.
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Dunbar, R. (2003). Evolution of the social brain. Science, 302(5648), 1160–1161.
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de Waal, F. B., & Johanowicz, D. L. (1993). Modification of reconciliation behavior through social experience: an experiment with two macaque species. Child Dev, 64(3), 897–908.
Abstract: Reconciliation, defined as a friendly reunion between former opponents shortly after an aggressive encounter, is common in the stumptail macaque (Macaca arctoides) but rare in the rhesus macaque (M. mulatta). Juveniles of the two species were cohoused for 5 months, after which they were observed with conspecifics only. Control rhesus monkeys, matched in age and sex to the experimental subjects, went through the same procedure without exposure to the other species. A threefold increase in the proportion of reconciled fights was measured in the rhesus subjects. The difference emerged gradually during cohousing with the tutor species and was sustained following removal of this species. Other behavior, such as grooming and aggression, decreased over time. It is suggested that the social attitude of the subjects was affected through contact with a species characterized by a more relaxed dominance style.
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Seyfarth, R. M. (1977). A model of social grooming among adult female monkeys. J. Theor. Biol., 65(4), 671–698.
Abstract: Grooming networks among adult female monkeys exhibit two similar features across a number of different species. High-ranking animals receive more grooming than others, and the majority of grooming occurs between females of adjacent rank. A theoretical model which duplicates these features is presented, and the properties of the model are used to explain the possible causation and function of female grooming behaviour. The model illustrates how relatively simple principles governing the behaviour of individuals may be used to explain more complex aspects of the social structure of non-human primate groups.
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Sinha, A. (1998). Knowledge acquired and decisions made: triadic interactions during allogrooming in wild bonnet macaques, Macaca radiata. Philos Trans R Soc Lond B Biol Sci, 353(1368), 619–631.
Abstract: The pressures of developing and maintaining intricate social relationships may have led to the evolution of enhanced cognitive abilities in many nonhuman primates. Knowledge of the dominance ranks and social relationships of other individuals, in particular, is important in evaluating one's position in the rank hierarchy and affiliative networks. Triadic interactions offer an excellent opportunity to examine whether decisions are taken by individuals on the basis of such knowledge. Allogrooming supplants among wild female bonnet macaques (macaca radiata) usually involved the subordinate female of a grooming dyad retreating at the approach of a female dominant to both members of the dyad. In a few exceptional cases, however, the dominant member of the dyad retreated; simple non-cognitive hypotheses involving dyadic rank differences and agonistic relationships failed to explain this phenomenon. Instead, retreat by the dominant individual was positively correlated with the social attractiveness of her subordinate companion (as measured by the duration of grooming received by the latter from other females in the troop). This suggests that not only does an individual evaluate relationships among other females, but does so on the basis of the amount of grooming received by them. Similarly, the frequency of approaches received by any female was correlated with her social attractiveness when she was the dominant member of the dyad, but not when she was the subordinate. This indicated that approaching females might be aware of the relative dominance ranks of the two allogrooming individuals. In logistic regression analyses, the probability of any individual retreating was found to be influenced more by her knowledge of her rank difference with both the other interactants, rather than by their absolute ranks. Moreover, information about social attractiveness appeared to be used in terms of correlated dominance ranks. The nature of knowledge acquired by bonnet macaque females may thus be egotistical in that other individuals are evaluated relative to oneself, integrative in that information about all other interactants is used simultaneously, and hierarchical in the ability to preferentially use certain categories of knowledge for the storage of related information from other domains.
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Seyfarth, R. M., & Cheney, D. L. (1984). Grooming, alliances and reciprocal altruism in vervet monkeys. Nature, 308(5959), 541–543.
Abstract: Reciprocal altruism refers to the exchange of beneficial acts between individuals, in which the benefits to the recipient exceed the cost to the altruist. Theory predicts that cooperation among unrelated animals can occur whenever individuals encounter each other regularly and are capable of adjusting their cooperative behaviour according to experience. Although the potential for reciprocal altruism exists in many animal societies, most interactions occur between closely related individuals, and examples of reciprocity among non-kin are rare. The field experiments on vervet monkeys which we present here demonstrate that grooming between unrelated individuals increases the probability that they will subsequently attend to each others' solicitations for aid. Vervets appear to be more willing to aid unrelated individuals if those individuals have behaved affinitively toward them in the recent past. In contrast, recent grooming between close genetic relatives appears to have no effect on their willingness to respond to each other's solicitations for aid.
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Newton-Fisher, N. E., & Lee, P. C. (2011). Grooming reciprocity in wild male chimpanzees. Anim. Behav., 81(2), 439–446.
Abstract: Understanding cooperation between unrelated individuals remains a central problem in animal behaviour; evolutionary mechanisms are debated, and the importance of reciprocity has been questioned. Biological market theory makes specific predictions about the occurrence of reciprocity in social groups; applied to the social grooming of mammals, it predicts reciprocity in the absence of other benefits for which grooming can be exchanged. Considerable effort has been made to test this grooming trade model in nonhuman primates; such studies show mixed results, but may be confounded by kin effects. We examined patterns of reciprocity within and across bouts, and tested predictions of the grooming trade model, among wild male chimpanzees, Pan troglodytes: a system with negligible kin effects. In accord with the model's expectations, we found that some grooming was directed by lower- to higher-ranked individuals, and that, on average, higher-ranked individuals groomed more reciprocally. We found no support, however, for a prediction that more reciprocity should occur between individuals close in rank. For most dyads, reciprocity of effort occurred through unbalanced participation in grooming bouts, but reciprocity varied considerably between dyads and only a small proportion showed strongly reciprocal grooming. Despite this, each male had at least one reciprocal grooming relationship. In bouts where both individuals groomed, effort was matched through mutual grooming, not alternating roles. Our results provide mixed support for the current grooming trade, biological market model, and suggest that it needs to incorporate risks of currency inflation and cheating for species where reciprocity can be achieved through repeated dyadic interactions.
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de Waal, F. B., & Seres, M. (1997). Propagation of handclasp grooming among captive chimpanzees. Am. J. Primatol., 43(4), 339–346.
Abstract: A grooming posture previously reported for two wild chimpanzee (Pan troglodytes) communities developed spontaneously in a captive group of the same species. This offered a unique opportunity to follow the propagation of a new social custom. The posture consists of two partners grasping hands--either both right hands or both left hands--and raising the arms in an A-frame above their heads while mutually grooming with their free hands. The propagation of this pattern was followed over a 5 year period. In the beginning, handclasps were always initiated by the same adult female. This female initiated the posture mainly with her adult female kin. In subsequent years, these relatives became frequent participants in the posture with each other as well as with nonrelatives. Over the years the posture increased in frequency and duration and spread to the majority of adults and also to a few adolescents and older juveniles. The pattern persisted after removal of the apparent originator.
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Kimura, R. (1998). Mutual grooming and preferred associate relationships in a band of free-ranging horses. Appl. Anim. Behav. Sci., 59(4), 265–276.
Abstract: Preferred associate (nearest neighbour) and mutual grooming relationships among mares, in an isolated family band of free-ranging horses (Equus caballus), were studied, and the structural and functional differences between these two relationships were examined. The frequent partners accompanying the mare were not the same in both these relationships (p<0.05) and mares changed their partners during the study period between 1988-1990. Individual horses of similar rank tended to remain closer together in both winter and summer. Aggressive-submissive behaviour was so infrequent during spring that rank determinations could not be made; however, in fall, although rank could be determined, rank was not correlated with nearest neighbour. Three subgroups, based on preferred associate relationships in summer, fall and winter, directly reflected the age and social rank of the mares in the group. Individual horses of higher rank tended to have many partners in winter, while individuals of lower rank had fewer. There was no significant correlation between the frequency of mutual grooming and individual rank. The mutual grooming relationship was strongly influenced by seasonal changes as the relative amount of grazing time per day increased. Thus, the frequency of mutual grooming was lowest in winter and highest in summer. The mutual grooming relationship was based on the bonds between individual horses, which were little influenced by social rank. Lower ranking individuals tended to have a greater variety of grooming partners in summer.
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Assersohn, C., Whiten, A., Kiwede, Z. T., Tinka, J., & Karamagi, J. (2004). Use of leaves to inspect ectoparasites in wild chimpanzees: a third cultural variant? Primates, 45(4), 255–258.
Abstract: We report 26 cases of using leaves as tools with which wild chimpanzees (Pan troglodytes schweinfurthii) in the Sonso community, Budongo Forest, Uganda, appeared to inspect objects removed during grooming. Careful removal of potential ectoparasites and delicate lip or manual placement on leaves followed by intense visual examination characterised this behaviour. It appears to be done to judge whether either ingestion or discarding is most appropriate, the former occurring in most cases. This behaviour may represent a third variant of ectoparasite handling, different from those described at Tai and Gombe, yet sharing features with the latter. These two East African techniques may thus have evolved from leaf grooming.
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