Abstract: The traditional notion of aggression as an antisocial instinct is being replaced by a framework that considers it a tool of competition and negotiation. When survival depends on mutual assistance, the expression of aggression is constrained by the need to maintain beneficial relationships. Moreover, evolution has produced ways of countering its disruptive consequences. For example, chimpanzees kiss and embrace after fights, and other nonhuman primates engage in similar “reconciliations.” Theoretical developments in this field carry implications for human aggression research. From families to high schools, aggressive conflict is subject to the same constraints known of cooperative animal societies. It is only when social relationships are valued that one can expect the full complement of natural checks and balances.

Abstract: Social dominance is usually viewed from the perspective of intragroup competition over access to limited resources. The present paper, while not denying the importance of such competition, discusses the dominance concept among monkeys and apes in the context of affiliative bonding, social tolerance, and the reconciliation of aggressive conflicts. Two basic proximate mechanisms are supposed to provide a link between dominance and interindividual affiliation, namely, formalization of the dominance relationship (i.e., unequivocal communication of status), and conditional reassurance (i.e., the linkage of friendly coexistence to formalization of the relationship). Ritualized submission is imposed upon losers of dominance struggles by winners; losers are offered a “choice” between continued hostility or a tolerant relationship with a clearly signalled difference in status. If these two social mechanisms are lacking, aggression is bound to have dispersive effects. In their presence, aggression becomes a well-integrated, even constructive component of social life. In some higher primates this process of integration has reached the stage where status differences are strongly attenuated. In these species, sharing and trading can take the place of overt competition. The views underlying this “reconciled hierarchy” model are only partly new, as is evident from a review of the ethological literature. Many points are illustrated with data on a large semi-captive colony of chimpanzees (Pan troglodytes), particularly data related to striving for status, reconciliation behavior, and general association patterns. These observations demonstrate that relationships among adult male chimpanzees cannot be described in terms of a dichotomy between affiliative and antagonistic tendencies. Male bonding in this species has not been achieved by an elimination of aggression, but by a set of powerful buffering mechanisms that mitigate its effects. Although female chimpanzees do exhibit a potential for bonding under noncompetitive conditions, they appear to lack the buffering mechanisms of the males.

Abstract: Lateralization of emotions has received great attention in the last decades, both in humans and animals, but little interest has been given to side bias in perceptual processing. Here, we investigated the influence of the emotional valence of stimuli on visual and olfactory explorations by horses, a large mammalian species with two large monocular visual fields and almost complete decussation of optic fibres. We confronted 38 Arab mares to three objects with either a positive, negative or neutral emotional valence (novel object). The results revealed a gradient of exploration of the 3 objects according to their emotional value and a clear asymmetry in visual exploration. When exploring the novel object, mares used preferentially their right eyes, while they showed a slight tendency to use their left eyes for the negative object. No asymmetry was evidenced for the object with the positive valence. A trend for an asymmetry in olfactory investigation was also observed. Our data confirm the role of the left hemisphere in assessing novelty in horses like in many vertebrate species and the possible role of the right hemisphere in processing negative emotional responses. Our findings also suggest the importance of both hemispheres in the processing positive emotions. This study is, to our knowledge, the first to demonstrate clearly that the emotional valence of a stimulus induces a specific visual lateralization pattern.

Abstract: In most cooperatively breeding birds and mammals, reproductive rates are lower for social subordinates than for dominants, and it is common for reproduction in subordinates to be completely suppressed. Early research conducted in captivity showed that losing fights can increase glucocorticoid (GC) secretion, a general response to stress. Because GCs can suppress reproduction, it has been widely argued that chronic stress might underlie reproductive suppression of social subordinates in cooperative breeders. Contradicting this hypothesis, recent studies of cooperative breeders in the wild show that dominant individuals have elevated GCs more often than do subordinates. The findings that elevated GCs can be a consequence of subordination or a cost of dominance complicate the conventional view of social stress, with broad ramifications for the evolution of dominance and reproductive suppression.

Abstract: Patterns of aggressive and affiliative behavior, such as counter aggression and reconciliation, are said to covary in the genus Macaca; this is referred to as the systematic variation hypothesis. These behavior patterns constitute a species dominance style. Van Schaik's [1989] socioecological model explains dominance style in macaques in terms of within- and between-group contest competition. Dominance style is also said to correlate with phylogeny in macaques. The present study was undertaken to examine phylogenetic and socioecological explanations of dominance style, as well as the systematic variation hypothesis. We collected data on counter aggression and reconciliation from a habituated group of Assamese macaques (Macaca assamensis) at the Tukeswari Temple in Assam, India. The proportion of agonistic episodes that involved counter aggression was relatively low. Counter aggression, however, occurred more often among males than among females, and it was most common when females initiated aggression against males. The conciliatory tendency for this group of Assamese macaques was 11.2%. The frequency of reconciliation was low for fights among males and for fights among females, but reconciliation was particularly rare for opposite-sexed opponents. Female social relationships were consistent with the systematic variation hypothesis, and suggest a despotic dominance style. A despotic dominance style in Assamese macaques weakens the correlation between dominance style and phylogeny in macaques, but it is not inconsistent with the socioecological model. Male-female relationships were not well explained by the despotic-egalitarian framework, and males may well have more tolerant social relationships than do females. Sex differences need to be considered when categorizing species according to dominance style.