Japan

In cultural transmission, information flows from ‘producers’ to ‘receivers’. Transmission biases such as content-, model- and frequency-based biases, which modulate the adoption of cultural traits by receivers, have been explored in depth. We focus instead on a bias on production and compare transmission fidelity when producers either intend to teach or intend to reproduce socially acquired information.

Eighty participants were asked to read a story and reproduce it either in order to ‘teach it to someone else’ or just ‘recall it as accurately as possible’. In order to test whether differences in fidelity between these two tasks were related to information encoding (during reading) or to reproduction, we also manipulated the timing of instructions: Half of the participants were informed of the task (Teach or Recall) Before reding the story and the other half, After reading the story. Participants were arranged in 20 transmission chains of 4 generations. The first generation in each chain read a text about the environment (from Mesoudi et al., 2006), and subsequent generations read the previous participant’s output story. We measured two aspect of fidelity: Quantity and Accuracy of information retained over generations. 

We found that being informed of the task Before reading the story led to higher Accuracy and Quantity than being informed After reading. Surprisingly, Teaching yielded lower Accuracy than Recall, but both resulted in similar Quantity retained. Additional analyses revealed differences in the content of the information under Teaching and Recall. We conclude that aspects of cultural transmission pertaining to production, in particular, intention to teach vs reproduce, influence transmission dynamics and therefore need to be integrated in models of cultural evolution.

Reference
Mesoudi, A., Whiten, A., &amp; Dunbar, R. (2006). A bias for social information in human cultural transmission. British Journal of Psychology, 97(3), 405–423.

Cultural Evolution Society 2021

Effects of intent (teaching vs accurate reproduction) on the cultural evolution of narratives

### Conference Welcome

Welcome to the third Cultural Evolution Society Conference, CES2021. In the conference, which will be held from June 9-11, 2021, about 180 researchers from East Asia, Oceania, Middle East, Europe, North and South America give presentations on their latest research advancing the evolutionary understanding of human and nonhuman animal culture.

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Registration fee

In cultural transmission, information flows from ‘producers’ to ‘receivers’. Transmission biases such as content-, model- and frequency-based biases, which modulate the adoption of cultural traits by receivers, have been explored in depth. We focus instead on a bias on production and compare transmission fidelity when producers either intend to teach or intend to reproduce socially acquired information.

Eighty participants were asked to read a story and reproduce it either in order to ‘teach it to someone else’ or just ‘recall it as accurately as possible’. In order to test whether differences in fidelity between these two tasks were related to information encoding (during reading) or to reproduction, we also manipulated the timing of instructions: Half of the participants were informed of the task (Teach or Recall) Before reding the story and the other half, After reading the story. Participants were arranged in 20 transmission chains of 4 generations. The first generation in each chain read a text about the environment (from Mesoudi et al., 2006), and subsequent generations read the previous participant’s output story. We measured two aspect of fidelity: Quantity and Accuracy of information retained over generations. 

We found that being informed of the task Before reading the story led to higher Accuracy and Quantity than being informed After reading. Surprisingly, Teaching yielded lower Accuracy than Recall, but both resulted in similar Quantity retained. Additional analyses revealed differences in the content of the information under Teaching and Recall. We conclude that aspects of cultural transmission pertaining to production, in particular, intention to teach vs reproduce, influence transmission dynamics and therefore need to be integrated in models of cultural evolution.

Reference
Mesoudi, A., Whiten, A., & Dunbar, R. (2006). A bias for social information in human cultural transmission. British Journal of Psychology, 97(3), 405–423.

technical paper

People often attribute rumours to an individual in a knowledgeable position two steps removed from them (a credible friend of a friend), such as ‘my friend’s father, who’s a cop, told me about a serial killer in town’. Little is known about the influence of such attributions on rumour propagation, or how they are maintained when the rumour is transmitted. In four studies (N = 1824) participants exposed to a rumour and asked to transmit it overwhelmingly attributed it either to a credible friend of a friend, or to a generic friend (e.g. ‘a friend told me about a serial killer in town’). In both cases, participants engaged in source shortening: e.g. when told by a friend that ‘a friend told me ...’ they shared the rumour as coming from ‘a friend’ instead of ‘a friend of friend’. Source shortening and reliance on credible sources boosted rumour propagation by increasing the rumours’ perceived plausibility and participants’ willingness to share them. Models show that, in linear transmission chains, the generic friend attribution dominates, but that allowing each individual to be exposed to the rumour from several sources enables the maintenance of the credible friend of a friend attribution.

It happened to a friend of a friend: inaccurate source reporting in rumour diffusion

Military personnel in industrialized societies often develop posttraumatic stress disorder (PTSD) during combat. It is unclear whether combat-related PTSD is a universal evolutionary response to danger or a culture-specific syndrome of industrialized societies. We interviewed 218 Turkana pastoralist warriors in Kenya, who engage in lethal cattle raids, about their combat experiences and PTSD symptoms. Turkana in our sample had a high prevalence of PTSD symptoms, but Turkana with high symptom severity had lower prevalence of depression-like symptoms than American service members with high symptom severity. Symptoms that facilitate responding to danger were better predicted by combat exposure, whereas depressive symptoms were better predicted by exposure to combat-related moral violations. The findings suggest that some PTSD symptoms stem from an evolved response to danger, while depressive PTSD symptoms may be caused by culturally specific moral norm violations.

Combat stress in a small-scale society suggests divergent genetic and cultural roots of PTSD symptoms

The existence of sharp stone tools is sometimes used as evidence for early cultural evolution in hominins. Yet, it is an open question whether these tools required cultural transmission of their underlying know-how. The main, but previously untested, alternative is that the know-how underlying these tools was the outcome of biologically evolved abilities (adaptations/exaptations). Here we tested – for the first time – whether non-human great apes may be spontaneously able to innovate the neccessary know-how to produce and use sharp stone tools. This required us to test apes in the absence of human enculturation and in the absence of human know-how demonstrations. Eleven chimpanzees were tested in this way. All proved motivated to engage in the tasks given, but not a single chimpanzee spontaneously made or used sharp stone tools. Our results stand in sharp contrast to the positive outcomes of earlier ape sharp stone tool experiments. However, all three apes that were previously tested (one orangutan and two bonobos) had received both human enculturation and human know-how demonstrations prior to their test (even active moulding of actions was sometimes applied). Human enculturation and/or human know-how demonstrations may thus be necessary before apes acquire sharp stone tool abilities. This would suggests that sharp stone tool manufacture and use has evolved – culturally and/or biologically – in the hominin lineage after the split between Homo and Pan.

Unenculturated chimpanzees fail to produce and use sharp stone tools in the absence of know-how demonstrations

Social learning in primates has been studied experimentally for over 120 years, yet until recently these efforts focused only on what one individual would learn from a single other. Evidence of group-wide traditions in the wild stimulated a shift in the present century to recognize the collective context of social learning, with the development of broader ‘diffusion experiments’ that have illuminated the nature and limits of transmission across communities of multiple individuals and then between them. Here we describe the results of two strands within our recent experiments that further explore the collective dimensions of culture and cumulative culture in chimpanzees. The first concerns collective innovation and cumulative culture. Exposing small communities of chimpanzees to contexts incorporating increasingly challenging, but more rewarding, tool use opportunities revealed solutions arising through the combination of different individuals’ discoveries, that spread to become shared innovations. The second strand is conformity, where experiments have yielded evidence of conformist changes from habitual techniques to alternatives displayed by a unanimous majority of others, but with a curious twist akin to quorum decision making, based on only a sample of those in the community. We discuss the implications of this array of findings in the context of related studies of both other primates and non-primate species, as well as for enhancing our understanding of the extraordinary forms that cumulative culture has taken in our own species, likely built on the foundations we can infer from studies of the primates with whom we share our most recent common ancestry.

Collective Knowledge and the Dynamics of Culture in Chimpanzees

Basic vocabulary lists are a popular data type in the field of phylogenetic linguistics because of the vertical signal the data carries. Interestingly, basic vocabulary also features borrowings. The horizontal influence can be understood as a proxy for population contacts as well because loanwords into basic vocabulary are most likely acquired in intimate contact situations. This is valuable information for multidisciplinary studies aiming to integrate information on contact events from various sciences to gain a better insight into the prehistory of a population. As basic vocabulary lists are widely available, they can inform of the known contact history for large groups of languages or even whole language families making wide-scale comparison possible.

We call the contact history of a language reflected by its loanwords the borrowing profile. In our paper, we compare the borrowing profiles mediated by the basic vocabulary of six well-studied Uralic languages to the borrowing profiles of the whole languages represented by large vocabulary stocks. We show that basic vocabulary provides an informative snapshot of the borrowing profile; however, the trace of prehistoric loanword layers is emphasized in basic vocabulary. Known sociolinguistic circumstances explain the differences in the borrowing profiles of basic and whole vocabulary.

Loanwords in basic vocabulary mediate the borrowing profile of a language

What we talk about when we talk about color

Storytelling, like language, is central to human cognition: it helps us process experiences (Wilkens et al, 2005), store memories (Nelson, 1993; Schank & Abelson, 1995), and form personal identities (Young & Saver, 2001; Yuval-Davis, 2006). Previous studies have used iterated learning to examine the role of cultural transmission in the evolution of language (Smith, Kirby & Brighton, 2003; Kirby, Cornish & Smith, 2008; Kirby, Griffiths & Smith, 2014), and reveal content biases for social and survival information in the transmission of narratives (Bartlett, 1920; Stubbersfield, Tehrani & Flynn, 2014; 2017). This experiment combined the transmission chain paradigm with task-based experiments (Bahrami et al, 2010; Bjørndahl et al, 2014; Thompson et al, 1993) to test whether exposure to social survival information through narrative improves performance in a social task: a game in which participants had to learn a set of novel, arbitrary social customs to succeed. In two conditions, participants then wrote either a story or list, designed to memorably communicate the customs to the next player, forming a transmission chain (see demo here: https://bit.ly/narrative-game). Scores in the task improved over generations in both conditions, supporting the hypothesis that narratives can effectively communicate social survival information in transmission. These results are compatible with Dunbar’s (1997) social brain hypothesis, the ‘problem simulation theory of storytelling’ (Gottschall, 2012 p. 63), and previous experimental work on content biases (Stubbersfield, Tehrani & Flynn 2014; 2017). We provide an experimental paradigm which can now be adapted to target more specific questions about the evolution of narratives.

True story: Narrative as an adaptation for the communication of social survival information

Swarm Robotics, which studies collective behaviors of large populations of robots with simple embodied cognition, is an ideal testbed for studying the cultural evolution of language. Our goal is to expand existing simulations in order to explore a dominant theory in evolutionary linguistics - the self-domestication hypothesis - which suggests that reduced reactive aggression led to the sophistication of the cultural niche, enabling the complexification of languages. 

Current swarm robotics models, however, lack several crucial features that are considered prerequisites for this process. Robots are typically collaborative, homogenous, with little to no memory. To mimic self-domestication, an evolutionary advantage for prosociality needs to be introduced, and robots need to be treated as distinct individuals. 

In our model, robots explore their environment while playing a language game. Crucially, we include two novel features: (1) robot individuation: robots have a partner-specificity memory, keeping track of the outcomes of past interactions with specific robots; (2) parameterizable prosociality: robots’ tendency to interact is based on experience: successful communications between robots reduce their aggression toward each other and increase their chance to interact again. With these manipulations, community structure should emerge (robots favoring interaction with some robots over others, i.e., “in-group” bias), and different lexicons should stabilize in different sub-groups in the swarm despite their physical proximity. 

Future steps will introduce an underlying task requiring robots to cooperate using their shared language to achieve a goal. In this context, more complex language structures should evolve, demonstrating the positive feedback loop between increased self-domestication and language complexity.

A swarm robotics model of the cultural evolution of language

Conventions form an essential part of human social and cultural behaviour and may also be important to other animals. Yet, despite the wealth of evidence that has accumulated for culture in non-human animals, we know surprisingly little about non-human conventions beyond a few rare examples. We follow the literature in behavioural ecology and evolution and define conventions as behaviours that solve a coordination problem in which two or more individuals need to display complementary behaviour to obtain a mutually beneficial outcome. We review and discuss the literature on conventions in non-human primates and come to the conclusion that all the ingredients for conventions to emerge are present and therefore that they ought to be more frequently observed. We probe emergence of conventions by using a unique novel experimental system in which two baboons (Papio papio) can voluntarily participate together in touch-screen based cognitive testing and we show that conventions readily emerge in our experimental setup and that they share three fundamental properties of human conventions (arbitrariness, stability and efficiency). These results question the idea that imitation is necessary to establish conventions.

The experimental emergence of convention in a non-human primate

While previous studies testing evolutionary models of religious morality found that beliefs in moralizing and punitive gods decrease local favoritism and increase resource-sharing with distant co-religionists, the effects of beliefs related to local supernatural agents have not been extensively explored. Nam (the spirit of a deceased person) beliefs are quite ambiguous because the spirit may be linked to ancestor worship but also to the practice of sorcery (illegal in Mauritius). Importantly, previous studies suggested that sorcery beliefs and practices can have a damaging impact on social bonds and trust, but such research is often limited by social stigma associated with sorcery and relevant comparison with other local deities is often missing. We show that endorsing the sorcery mode of belief in nam together with performing rituals toward nam was associated with larger probability of breaking the game rules for selfish outcomes in the Random Allocation Game (compared to the ancestor worship mode).

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