Social Attention in the Two Species of Pan: Bonobos Make More Eye Contact than Chimpanzees

Humans’ two closest primate living relatives, bonobos and chimpanzees, differ behaviorally, cognitively, and emotionally in several ways despite their general similarities. While bonobos show more affiliative behaviors towards conspecifics, chimpanzees display more overt and severe aggression against conspecifics. From a cognitive standpoint, bonobos perform better in social coordination, gaze-following and food-related cooperation, while chimpanzees excel in tasks requiring extractive foraging skills. We hypothesized that attention and motivation play an important role in shaping the species differences in behavior, cognition, and emotion. Thus, we predicted that bonobos would pay more attention to the other individuals’ face and eyes, as those are related to social affiliation and social coordination, while chimpanzees would pay more attention to the action target objects, as they are related to foraging. Using eye-tracking we examined the bonobos’ and chimpanzees’ spontaneous scanning of pictures that included eyes, mouth, face, genitals, and action target objects of conspecifics. Although bonobos and chimpanzees viewed those elements overall similarly, bonobos viewed the face and eyes longer than chimpanzees, whereas chimpanzees viewed the other elements, the mouth, action target objects and genitals, longer than bonobos. In a discriminant analysis, the individual variation in viewing patterns robustly predicted the species of individuals, thus clearly demonstrating species-specific viewing patterns. We suggest that such attentional and motivational differences between bonobos and chimpanzees could have partly contributed to shaping the species-specific behaviors, cognition, and emotion of these species, even in a relatively short period of evolutionary time.     

Imitation Is Necessary for Cumulative Cultural Evolution in an Unfamiliar,Opaque Task

Imitation, the replication of observed behaviors, has been proposed as the crucial social learning mechanism for the generation of humanlike cultural complexity. To date, the single published experimental microsociety study that tested this hypothesis found no advantage for imitation. In contrast, the current paper reports data in support of the imitation hypothesis. Participants in “microsociety” groups built weight-bearing devices from reed and clay. Each group was assigned to one of four conditions: three social learning conditions and one asocial learning control condition. Groups able to observe other participants building their devices, in contrast to groups that saw only completed devices, show evidence of successive improvement. These results are consistent with the hypothesis that imitation is required for cumulative cultural evolution. This study adds crucial data for understanding why imitation is needed for cultural accumulation, a central defining feature of our species.     

Exploring the Social Environment: a Developmental Study of Teasing in Chimpanzees

Long-term data on the occurrence of “teasing” in young chimpanzees living in the Arnhem Zoo chimpanzee colony are presented. They strengthen the hypotheses—presented in earlier papers—concerning the existence of two functional forms of this so-called quasi-aggressive behaviour and provide insight into the way in which they develop. Developmental changes are visible both in the performance of quasi-aggressive behaviour and in the effects evoked by the behaviour. The purpose of the reducing uncertainty type of quasi-aggressive behaviour, performed by male and female youngsters towards adult females, is to obtain more predictable responses. As youngsters grow older, they engage in this behaviour also to gain control over the responses of the target animals. Eventually, the quasi-aggressive behaviour of male youngsters develops into adult-like bluff and attack behaviour the purpose of which is to establish dominance relationships. The investigating authority type of quasi-aggressive behaviour, directed towards adult males, is associated increasingly with the exercise of power by the target males. The youngsters increasingly behave submissively towards the males and direct quasi-aggressive behaviour especially towards the alpha-male at moments when he is bluffing or involved in other conspicuous social interactions. These and other changes in the relationship between adult males and male youngsters are already visible well before the onset of puberty in the youngsters. It is discussed in how far the development of these exploratory aggression types involves social learning processes and how this fits in with current concepts concerning the development of aggressive behaviour.     

Social Network Analysis Shows Direct Evidence for Social Transmission of Tool Use in Wild Chimpanzees

Social network analysis methods have made it possible to test whether novel behaviors in animals spread through individual or social learning. To date, however, social network analysis of wild populations has been limited to static models that cannot precisely reflect the dynamics of learning, for instance, the impact of multiple observations across time. Here, we present a novel dynamic version of network analysis that is capable of capturing temporal aspects of acquisition—that is, how successive observations by an individual influence its acquisition of the novel behavior. We apply this model to studying the spread of two novel tool-use variants, “moss-sponging” and “leaf-sponge re-use,” in the Sonso chimpanzee community of Budongo Forest, Uganda. Chimpanzees are widely considered the most “cultural” of all animal species, with 39 behaviors suspected as socially acquired, most of them in the domain of tool-use. The cultural hypothesis is supported by experimental data from captive chimpanzees and a range of observational data. However, for wild groups, there is still no direct experimental evidence for social learning, nor has there been any direct observation of social diffusion of behavioral innovations. Here, we tested both a static and a dynamic network model and found strong evidence that diffusion patterns of moss-sponging, but not leaf-sponge re-use, were significantly better explained by social than individual learning. The most conservative estimate of social transmission accounted for 85% of observed events, with an estimated 15-fold increase in learning rate for each time a novice observed an informed individual moss-sponging. We conclude that group-specific behavioral variants in wild chimpanzees can be socially learned, adding to the evidence that this prerequisite for culture originated in a common ancestor of great apes and humans, long before the advent of modern humans.     

Food Acceptance and Social Learning Opportunities in Semi‐Free Eastern Chimpanzees (Pan troglodytes schweinfurthii)

When confronted with novel foods, chimpanzees’ responses combine a mixture of curiosity and cautiousness. Once the item is in the mouth, the initial cautiousness is followed by an aversion to bitter taste that is mediated mainly by the TAS2R gene family. For instance, variations on the TAS2R38 locus which has been studied extensively in humans have been associated with different acceptance of bitter substances. Surprisingly, while cautiousness and bitter taste aversion were selected to prevent any risk of poisoning, very few studies on novel food acceptance have included the vegetative parts of plants. Moreover, the studies were usually carried out with captive apes faced to a very restricted variety of non‐toxic plants, hardly making the results representative. This study aims to replicate previous findings obtained in zoos while controlling for these limitations. We provided nine subgroups of eastern chimpanzees (Pan troglodytes schweinfurthii) living in the Ugandan sanctuary of Ngamba Island with novel plants known to be consumed by wild chimpanzees of the same subspecies, as well as domestic plants, wild sapota fruit and grey clay used by human local communities. We also genotyped their TAS2R38 gene. Our results confirm the very low genetic heterogeneity for TAS2R38 in this chimpanzee subspecies. Chimpanzees were particularly cautious towards the vegetative parts of novel plants, likely reflecting their behavioural strategy for avoiding toxic compounds. We also confirmed their higher propensity towards testing sapota and clay, reflecting their ability to expand their diet. In contrast with the results found in zoos, familiar and novel less‐palatable vegetative parts of plants did not elicit many interindividual observations. This may be explained by the items presented, which could have been so novel to be considered as enrichment in captive conditions, where the apes are rarely exposed to plants.     

Effects of Conformism on the Cultural Evolution of Social Behaviour

Models of cultural evolution study how the distribution of cultural traits changes over time. The dynamics of cultural evolution strongly depends on the way these traits are transmitted between individuals by social learning. Two prominent forms of social learning are payoff-based learning (imitating others that have higher payoffs) and conformist learning (imitating locally common behaviours). How payoff-based and conformist learning affect the cultural evolution of cooperation is currently a matter of lively debate, but few studies systematically analyse the interplay of these forms of social learning. Here we perform such a study by investigating how the interaction of payoff-based and conformist learning affects the outcome of cultural evolution in three social contexts. First, we develop a simple argument that provides insights into how the outcome of cultural evolution will change when more and more conformist learning is added to payoff-based learning. In a social dilemma (e.g. a Prisoner’s Dilemma), conformism can turn cooperation into a stable equilibrium; in an evasion game (e.g. a Hawk-Dove game or a Snowdrift game) conformism tends to destabilize the polymorphic equilibrium; and in a coordination game (e.g. a Stag Hunt game), conformism changes the basin of attraction of the two equilibria. Second, we analyse a stochastic event-based model, revealing that conformism increases the speed of cultural evolution towards pure equilibria. Individual-based simulations as well as the analysis of the diffusion approximation of the stochastic model by and large confirm our findings. Third, we investigate the effect of an increasing degree of conformism on cultural group selection in a group-structured population. We conclude that, in contrast to statements in the literature, conformism hinders rather than promotes the evolution of cooperation.     

The Care and Management of Captive Chimpanzees Workshop: Managing Social Behavior

Urination and defecation outside the litter box is one of the most common behavior problems reported by cat caretakers and the most common behavioral reason that results in the relinquishment of cats to shelters. A physical examination, laboratory tests, and a thorough behavioral history are necessary to differentiate between the diagnoses of disease, marking, and inappropriate elimination. This study followed up on the outcome of cats who were treated for inappropriate elimination. Fifty-eight caregivers completed a telephone questionnaire 12 to 54 months after treatment was initiated. Twenty-seven (47%) of caregivers felt their cat was cured, 15 (26%) felt their cat was much better, 8 (14%) slightly better, 6 (10%) the same, and 2 (3%) worse. Forty caregivers (67%) observed a 90% to 100% reduction in frequency. There was a significant association between the caregivers' perception of treatment outcome and percentage reduction in frequency. There was a significant association between caregivers compliance and outcome. The results of this study give caregivers a valid and promising alternative to relinquishment for inappropriate elimination problems.     

Direct Male Care and Hominin Evolution: Why Male–Child Interaction Is More Than a Nice Social Idea

ABSTRACT  Early members of the genus Homo experienced heightened absolute metabolic costs, partially owing to increases in body size. However, as is characteristic of modern humans, they also likely began reproducing with shortened interbirth intervals. Male investment in offspring may help explain how this life history shift occurred. Evolutionary models of hominin male investment in offspring have traditionally focused on provisioning of females and young, yet the extent to which direct male care of offspring was evolutionarily important, from an energetic perspective, is largely unaddressed. I propose an evolutionary model of direct male care, demonstrating that males could have helped reduce the energetic burden of caregiving placed on mothers by carrying young. In doing so, males would have assisted females in achieving and maintaining an energetic condition sufficient for reproduction, thereby hastening the advent of shortened interbirth intervals that played a formative role in the success of our genus.     

Experimental Evolution Reveals a Genetic Basis for Membrane-Associated Virus Release

Many animal viruses replicate and are released from cells in close association to membranes. However, whether this is a passive process or is controlled by the virus remains poorly understood. Importantly, the genetic basis and evolvability of membrane-associated viral shedding have not been investigated. To address this, we performed a directed evolution experiment using coxsackievirus B3, a model enterovirus, in which we repeatedly selected the free-virion or the fast-sedimenting membrane-associated viral subpopulations. The virus responded to this selection regime by reproducibly fixing a series of mutations that altered the extent of membrane-associated viral shedding, as revealed by full-genome ultra-deep sequencing. Specifically, using site-directed mutagenesis, we showed that substitution N63H in the viral capsid protein VP3 reduced the ratio of membrane-associated to free viral particles by 2 orders of magnitude. These findings open new avenues for understanding the mechanisms and implications of membrane-associated viral transmission.     

More Tweets,More Votes: Social Media as a Quantitative Indicator of Political Behavior

Is social media a valid indicator of political behavior? There is considerable debate about the validity of data extracted from social media for studying offline behavior. To address this issue, we show that there is a statistically significant association between tweets that mention a candidate for the U.S. House of Representatives and his or her subsequent electoral performance. We demonstrate this result with an analysis of 542,969 tweets mentioning candidates selected from a random sample of 3,570,054,618, as well as Federal Election Commission data from 795 competitive races in the 2010 and 2012 U.S. congressional elections. This finding persists even when controlling for incumbency, district partisanship, media coverage of the race, time, and demographic variables such as the district''s racial and gender composition. Our findings show that reliable data about political behavior can be extracted from social media.     

Ontogeny of a Social Custom in Wild Chimpanzees: Age Changes in Grooming Hand‐Clasp at Mahale

Among cultural behaviors of chimpanzees, the developmental processes of complex skills involved in tool use are relatively well known. However, few studies have examined the ontogeny of social customs that do not require complex skills. Thus, in this study, we describe the developmental process of the grooming hand‐clasp (GHC), one of the well‐known social customs of chimpanzees at Mahale. We have collected 383 cases of GHC where at least one of the participants was 15 years old or younger during 1994–2007. First performances of GHC with the mother were observed at around 4–6 years old; the earliest observed age was 4 years and 4 months old. The first performances of GHC with nonrelated females were at around age 9 years, and those with adult males at around 11 years. However, some orphans engaged in GHC earlier than nonorphans. By gradually expanding GHC partners from the mother to other females and then to males, chimpanzees increased the number of GHC partners with age. Young males were observed to perform GHC with larger numbers of partners than were young females. GHC by young chimpanzees was shorter in duration than that among adults. Overall, the ontogeny of GHC showed several dissimilarities with that of tool use and was more an extension of the development of typical grooming behavior. For example, infants did not try to perform GHC initially; instead, mothers were more active in the earliest stages. These results suggest that not all socially learned cultural behaviors are acquired in the way of learning tool use. There may be various ways of learning behavioral patterns that are performed continuously in a group and that consequently comprise culture in chimpanzees. Am. J. Primatol. 75:186‐196, 2013. © 2012 Wiley Periodicals, Inc.     

Nesting Behavior of Chimpanzees: Implications for Censuses

Chimpanzees have been censused using nest counting techniques since the mid 1970s. The use of nest counts makes several assumptions which have never been tested: (a) that the visibility of nests does not change with the height of the nest in the canopy; (b) that weaned chimpanzees construct on average one nest per day; (c) that establishing census lines has no effect on the nesting behavior of the chimpanzees; and (d) that the presence of snare injuries, common in forests in eastern Africa, does not affect nest construction. Tests of these assumptions in the Budongo Forest in Uganda showed that visibility of nests at different heights in the canopy is not different from the true distribution of nests but that the other assumptions are false. Minimizing human use could limit the effects of line transects on censuses, but the other two assumptions need to be corrected for.     

Education Is Life Itself: Biological Evolution as a Model for Human Learning

Schooling often rests uneasily on presumed dichotomies between coverage and inquiry, skill development, and creativity. By drawing on the often under-recognized parallels between biological evolution and human learning, this essay argues that formal education needs and ought not to forego the unconscious exploratory processes of informal learning. Rather than posit as natural the cultural story that formal schooling must prepare students to integrate with given cultures and foreknowable futures, the evolutionary perspective shows that education is better thought of as preparing students to create cultures and to change, and foster change, in relation to unknown futures. The properties that distinguish formal from informal learning—conscious reflection and a degree of collective consensus about what constitutes knowledge at any given time—are, we argue, useful not as ends in themselves, but as tools for maximizing, sharing, and extending unconscious, evolutionary learning. Working with them as such offers a way out of some of education’s persistent problems. Two autobiographical case studies provide examples of these evolutionary changes and indicate pathways of inquiry by which to pursue them.