Call playback artificially generates a temporary cultural style of high affiliation in marmosets

Cultural variation can be conceptualised in two main ways: as culture-specific qualitative differences in behavioural form, and also as quantitative variation in performance of constellations of universal behaviours (cultural style). Despite observation of both types in wild non-human primates, diffusion of qualitative culture has been scrutinised extensively experimentally whilst within-species transmission of cultural style has remained entirely unexplored. Here we investigated whether a cultural style of high affiliation could be artificially generated in a nonhuman primate (Callithrix jacchus), by daily playback of conspecific affiliative calls simulating nearby amicable individuals. We found that vocalisation playback influenced monkeys to spend more time in affiliative behaviours outwith playback hours, relative to silent playback. The effect was specific to affiliation, with no impact on other categories of affect. This change did not persist into the final phase of observation after all playbacks were complete. Findings are consistent with a temporary shift in cultural style effected through vocalisation playback, supporting existence of this conception of culture in wild primates and indicating auditory social contagion as a potential diffusion mechanism. The method presented here will allow researchers to test hypotheses concerning cultural transmission of cultural style, and the underlying processes, across a range of contexts and species

Conformism in the food processing techniques of white-faced capuchin monkeys (Cebus capucinus)

Researchers of “culture” have long been interested in the role of social learning in establishing patterns of behavioral variation in wild animals, but very few studies examine this issue using a developmental approach. This 7-year study examines the acquisition of techniques used to process Luehea candida fruits in a wild population of white-faced capuchin monkeys, Cebus capucinus, residing in and near Lomas Barbudal Biological Reserve, Costa Rica. The two techniques for extracting seeds (pounding or scrubbing) were approximately equal in efficiency, and subjects experimented with both techniques before settling on one technique—typically the one they most frequently observed. In a sample of 106 subjects that had already settled on a preferred technique, the females adopted the maternal technique significantly more often than expected by chance, but the males did not. Using a longitudinal approach, I examined the acquisition of Luehea processing techniques during the first 5 years of life. Regression analysis revealed that the technique most frequently observed (measured as proportion of Luehea processing bouts observed that used pounding as opposed to scrubbing) significantly predicted the technique adopted by female observers, particularly in the second year of life; the amount of impact of the observed technique on the practiced technique was somewhat less significant for male observers. These results held true for (a) observations of maternal technique only, (b) observations of technique used by all individuals other than the mother, and (c) observations of maternal and non-maternal techniques combined

Universal Behaviors as Candidate Traditions in Wild Spider Monkeys

Candidate traditions were documented across three communities of wild spider monkeys (Ateles geoffroyi) using an a priori approach to identify behavioral variants and a statistical approach to examine differences in their proportional use. This methodology differs from previous studies of animal traditions, which used retrospective data and relied on the ‘exclusion method’ to identify candidate traditions. Our a priori approach increased the likelihood that behavior variants with equivalent functions were considered and our statistical approach enabled the proportional use of ‘universal’ behaviors, i.e., used across all communities, to be examined for the first time in any animal species as candidate traditions. Among universal behaviors we found 14 ‘community preferred’ variants. After considering the extent to which community preferred variants were due to ecological and, to a lesser degree, genetic differences, we concluded that at least six were likely maintained through social learning. Our findings have two main implications: (i) tradition repertoires could be larger than assumed from previous studies using the exclusion method; (ii) the relative use of universal behavior variants can reinforce community membership

Old stones' song: Use-wear experiments and analysis of the Oldowan quartz and quartzite assemblage from Kanjera South (Kenya)

Evidence of Oldowan tools by w2.6 million years ago (Ma) may signal a major adaptive shift in hominin evolution. While tool-dependent butchery of large mammals was important by at least 2.0 Ma, the use of artifacts for tasks other than faunal processing has been difficult to diagnose. Here we report on use-wear analysis ofw2.0 Ma quartz and quartzite artifacts from Kanjera South, Kenya. A use-wear framework that links processing of specific materials and tool motions to their resultant use-wear patterns was developed. A blind test was then carried out to assess and improve the efficacy of this experimental use-wear framework, which was then applied to the analysis of 62 Oldowan artifacts from Kanjera South. Usewear on a total of 23 artifact edges was attributed to the processing of specific materials. Use-wear on seven edges (30%) was attributed to animal tissue processing,corroborating zooarchaeological evidence for butchery at the site. Use-wear on 16 edges (70%)was attributed to the processing of plant tissues, including wood, grit-covered plant tissues that we interpret asunderground storage organs (USOs), and stems of grass or sedges. These results expand our knowledge of the suite of behaviours carried out in the vicinity of Kanjera South to include the processing of materials that would be ‘invisible’ using standard archaeological methods. Wood cutting and scraping may represent the production and/or maintenance of wooden tools. Use-wear related to USO processing extends the archaeological evidence for hominin acquisition and consumption of this resource by over 1.5 Ma. Cutting of grasses, sedges or reeds may be related to a subsistence task (e.g., grass seed harvesting, cutting out papyrus culm for consumption) and/or a non-subsistence related task (e.g., production of ‘twine,’ simple carrying devices, or bedding). These results highlight the adaptive significance of lithic technology for hominins at Kanjera

Human cumulative culture: a comparative perspective

Many animals exhibit social learning and behavioural traditions, but human culture exhibits unparalleled complexity and diversity, and is unambiguously cumulative in character. These similarities and differences have spawned a debate over whether animal traditions and human culture are reliant on homologous or analogous psychological processes. Human cumulative culture combines high-fidelity transmission of cultural knowledge with beneficial modifications to generate a ‘ratcheting’ in technological complexity, leading to the development of traits far more complex than one individual could invent alone. Claims have been made for cumulative culture in several species of animals, including chimpanzees, orang-utans and New Caledonian crows, but these remain contentious. Whilst initial work on the topic of cumulative culture was largely theoretical, employing mathematical methods developed by population biologists, in recent years researchers from a wide range of disciplines, including psychology, biology, economics, biological anthropology, linguistics and archaeology, have turned their attention to the experimental investigation of cumulative culture. We review this literature, highlighting advances made in understanding the underlying process of cumulative culture and emphasizing areas of agreement and disagreement amongst investigators in separate fields

Can traditions emerge from the interaction of stimulus enhancement and reinforcement learning? An experimental model

The study of social learning in captivity and behavioral traditions in the wild are two burgeoning areas of research, but few empirical studies have tested how learning mechanisms produce emergent patterns of tradition. Studies have examined how social learning mechanisms that are cognitively complex and possessed by few species, such as imitation, result in traditional patterns, yet traditional patterns are also exhibited by species that may not possess such mechanisms. We propose an explicit model of how stimulus enhancement and reinforcement learning could interact to produce traditions. We tested the model experimentally with tufted capuchin monkeys (Cebus apella), which exhibit traditions in the wild but have rarely demonstrated imitative abilities in captive experiments. Monkeys showed both stimulus enhancement learning and a habitual bias to perform whichever behavior first obtained them a reward. These results support our model that simple social learning mechanisms combined with reinforcement can result in traditional patterns of behavior