Filippo Aureli

Fission-Fusion Dynamics: New Research Frameworks

Renewed interest in fission‐fusion dynamics is due to the recognition that such dynamics may create unique challenges for social interaction and distinctive selective pressures acting on underlying communicative and cognitive abilities. New frameworks for integrating current knowledge on fission‐fusion dynamics emerge from a fundamental rethinking of the term “fission‐fusion” away from its current general use as a label for a particular modal type of social system (i.e., “fission‐fusion societies”). Specifically, because the degree of spatial and temporal cohesion of group members varies both within and across taxa, any social system can be described in terms of the extent to which it expresses fission‐fusion dynamics. This perspective has implications for socioecology, communication, cognitive demands, and human social evolution.

A modest proposal: displacement activities as an indicator of emotions in primates

Abstract Displacement activities are behaviour patterns (mostly body care activities) characterized by their apparent irrelevance to the situation in which they appear. Scratching, autogrooming, yawning and body shaking are among the most commonly reported displacement activities in non-human primates. A review of the primate literature indicates that displacement activities tend to occur in situations of psychosocial stress and that their frequency of occurrence is affected by anxiogenic and anxiolytic drugs. In the light of this evidence, it is suggested that displacement activities can be used as indicators of emotional states arising in a variety of primate social interactions. Methodological problems associated with such a use are discussed. The hypothesis that displacement activities may also have a communicative function in non-human primates is not supported adequately by available data.

Conflict resolution following aggression in gregarious animals: a predictive framework

Knowledge of how animals manage their conflicts is critical for understanding the dynamics of social systems. During the last two decades research on gregarious animals, especially primates, has focused on the mechanisms of conflict management, mainly on friendly postconflict reunions (also called ‘reconciliation’) in which former opponents exchange affiliative behaviour soon after an aggressive conflict. Our aim in this paper is to present a framework in which the costs and benefits of friendly postconflict reunions, both for each individual opponent and for their mutual relationship, are used to predict the patterning of postconflict resolution mechanisms in other gregarious animals. The framework predicts the occurrence of postconflict reunions in species that live in stable social units, have individualized relationships, and experience postconflict hostility, but especially in those in which intragroup aggression disrupts valuable relationships. The critical issue is whether aggressive conflicts occur between cooperative partners and whether the level of aggression is sufficient to jeopardize the benefits associated with such valuable relationships. We conclude by proposing four research priorities to evaluate the role of friendly reunions in negotiating relationships and the way they are themselves influenced by asymmetries in partner value and biological market effects.

Heart rate responses to social interactions in free-moving rhesus macaques (Macaca mulatta): a pilot study.

Heart rate telemetry was explored as a means to access animal emotion during social interactions under naturalistic conditions. Heart rates of 2 middle-ranking adult females living in a large group of rhesus macaques (Macaca mulatta) were recorded along with their behavior. Heart rate changes during 2 types of interactions were investigated, while controlling for the effects of posture and activity. The risk of aggression associated with the approach of a dominant individual was expected to provoke anxiety in the approachee. This prediction was supported by the heart rate increase after such an approach. No increase was found when the approacher was a kin or a subordinate individual. The tension-reduction function of allogrooming was also supported. Heart rate decelerated faster during the receipt of grooming than in matched control periods.

The Evolution of Self-Control

Significance Although scientists have identified surprising cognitive flexibility in animals and potentially unique features of human psychology, we know less about the selective forces that favor cognitive evolution, or the proximate biological mechanisms underlying this process. We tested 36 species in two problem-solving tasks measuring self-control and evaluated the leading hypotheses regarding how and why cognition evolves. Across species, differences in absolute (not relative) brain volume best predicted performance on these tasks. Within primates, dietary breadth also predicted cognitive performance, whereas social group size did not. These results suggest that increases in absolute brain size provided the biological foundation for evolutionary increases in self-control, and implicate species differences in feeding ecology as a potential selective pressure favoring these skills. Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scale required to rigorously test these explanations. Instead, previous research has largely relied on various measures of brain size as proxies for cognitive abilities. We experimentally evaluated these major evolutionary explanations by quantitatively comparing the cognitive performance of 567 individuals representing 36 species on two problem-solving tasks measuring self-control. Phylogenetic analysis revealed that absolute brain volume best predicted performance across species and accounted for considerably more variance than brain volume controlling for body mass. This result corroborates recent advances in evolutionary neurobiology and illustrates the cognitive consequences of cortical reorganization through increases in brain volume. Within primates, dietary breadth but not social group size was a strong predictor of species differences in self-control. Our results implicate robust evolutionary relationships between dietary breadth, absolute brain volume, and self-control. These findings provide a significant first step toward quantifying the primate cognitive phenome and explaining the process of cognitive evolution.

Stress reduction through consolation in chimpanzees

Consolation, i.e., postconflict affiliative interaction directed from a third party to the recipient of aggression, is assumed to have a stress-alleviating function. This function, however, has never been demonstrated. This study shows that consolation in chimpanzees reduces behavioral measures of stress in recipients of aggression. Furthermore, consolation was more likely to occur in the absence of reconciliation, i.e., postconflict affiliative interaction between former opponents. Consolation therefore may act as an alternative to reconciliation when the latter does not occur. In the debate about empathy in great apes, evidence for the stress-alleviating function of consolation in chimpanzees provides support for the argument that consolation could be critical behavior. Consistent with the argument that relationship quality affects their empathic responses, we found that consolation was more likely between individuals with more valuable relationships. Chimpanzees may thus respond to distressed valuable partners by consoling them, thereby reducing their stress levels, especially in the absence of reconciliation.

Post-Conflict Anxiety in Nonhuman Primates: The Mediating Role of Emotion in Conflict Resolution

During the last two decades, much research has focused on the mechanisms used by nonhuman primates for conflict resolution. Reconciliation, i.e., a friendly reunion between former opponents, has been reported in several primate species. Reconciliation seems to serve at least two functions. According to the Valuable Relationship Hypothesis, reconciliation restores the disturbed relationship between former opponents and, consequently, occurs more often between individuals with more valuable relationships. The Uncertainty-Reduction Hypothesis emphasizes the function of reconciliation to reduce anxiety and uncertainty in the recipient of aggression following a conflict. The study of post-conflict emotionality facilitates the integration of these two hypotheses. The present study focuses on the factors affecting post-conflict anxiety of the two former opponents. Post-conflict data of captive Barbary (Macaca sylvanus) and long-tailed macaques (Macaca fascicularis) are used here to examine patterns of anxiety-related behavior, such as self-scratching. The fact that in the first minutes following a conflict not only recipients of aggression but aggressors too increased the rate of scratching above baseline levels suggests that the risk of renewed attacks is unlikely to be the only reason for post-conflict anxiety. The quality of the relationship between former opponents was a good predictor of post-conflict scratching rates by the recipient of aggression: Rates were higher after conflicts between individuals with stronger affiliative relationships. This result was not due to differential risk of resuming hostilities or arousal resulting from the intensity of the previous conflict. This finding suggests that the disturbance of a valuable relationship due to the previous conflict (e.g., the potential loss of benefits provided by such relationships) is a major cause of post-conflict anxiety. In line with the Uncertainty-Reduction Hypothesis, the best way to cope with post-conflict anxiety is to reconcile and therefore restore the relationship. Higher levels of post-conflict anxiety should lead therefore to higher conciliatory tendency. This interpretation is supported by the fact that individuals with strong affiliative relationships reconcile more frequently than others, as predicted by the Valuable Relationship Hypothesis. The mediating role of emotions, such as post-conflict anxiety, is probably not limited to reconciliation. Other post-conflict interactions, such as consolation, triadic reconciliation, and mediation, are also likely to be better understood if future studies focus on the post-conflict emotions of the opponents and bystanders. Aggr. Behav. 23:315–328, 1997.

How does cognition evolve? Phylogenetic comparative psychology

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.

Response of fecal cortisol to stress in captive chimpanzees (Pan troglodytes)

This study examined whether fecal cortisol could be used as an index of stress responses. The stress responsiveness of fecal cortisol was tested with a stressor known to stimulate adrenal activity, the stress of anesthesia. Daily fecal and urine samples were collected from four captive chimpanzees (Pan troglodytes) before and after anesthetizations with Telazol®/Ketasat®. Tests of assay validity indicated that cortisol was measurable in chimpanzee fecal extracts. Fecal cortisol concentrations were significantly elevated 2 days after anesthetization, with elevations in seven of the eight treatments. The posttreatment peak was significantly greater than baseline values in three of the four subjects. Both fecal concentrations and proportionate increases in response to stress were significantly correlated with the corresponding values in urinary cortisol, confirming the stressfulness of these procedures and the stress responsiveness of fecal cortisol. These findings provide evidence for the application of fecal cortisol as a noninvasive index of physiologic stress in nonhuman primates. Am. J. Primatol. 44:57–69, 1998.

Differential kinship effect on reconciliation in three species of macaques ( Macaca fascicularis, M. fuscata , and M. sylvanus ).

Macaque societies are typically characterized by despotic dominance styles and strong bonds between related individuals. Interspecies variation in dominance style, however, has been recently documented. This study investigated whether kinship effects on social interactions vary depending on the species dominance style. Reconciliation was chosen as as a measure of relationship quality between group members. Groups of Japanese (Macaca fuscata) and long-tailed (M. fascicularis) macaques were selected for their highly despotic style, and Barbary (M. sylvanus) macaques were chosen for their lower level of despotism. The findings confirmed the hypothesis that kinship effects on reconciliation are stronger the more despotic the species is. Barbary macaque nonkin reconciled more often than nonkin of the other 2 species. In addition, the differences in reconciliation frequency between kin and nonkin were less pronounced among the less despotic Barbary macaques.