No abstract

Hominin reliance on Oldowan stone tools – which appear from 2.5mya and are believed to have been socially transmitted – has been hypothesised to have led to the evolution of teaching and language. Here we present an experiment investigating the efficacy of transmission of Oldowan tool-making skills along chains of adult human participants (N=184) using 5 different transmission mechanisms. Across six measures, transmission improves with teaching, and particularly with language, but not with imitation or emulation. Our results support the hypothesis that hominin reliance on stone tool-making generated selection for teaching and language and imply that (i) low-fidelity social transmission, such as imitation/emulation, may have contributed to the ~700,000 year stasis of the Oldowan technocomplex, and (ii) teaching or proto-language may have been pre-requisites for the appearance of Acheulean technology. This work supports a gradual evolution of language, with simple symbolic communication preceding behavioural modernity by hundreds of thousands of years.

Humans are characterized by an extreme dependence on culturally transmitted information. Such dependence requires the complex integration of social and asocial information to generate effective learning and decision making. Recent formal theory predicts that natural selection should favour adaptive learning strategies, but relevant empirical work is scarce and rarely examines multiple strategies or tasks. We tested nine hypotheses derived from theoretical models, running a series of experiments investigating factors affecting when and how humans use social information, and whether such behaviour is adaptive, across several computer-based tasks. The number of demonstrators, consensus among demonstrators, confidence of subjects, task difficulty, number of sessions, cost of asocial learning, subject performance and demonstrator performance all influenced subjects' use of social information, and did so adaptively. Our analysis provides strong support for the hypothesis that human social learning is regulated by adaptive learning rules.

Formal evolutionary models predict when individuals' rely on social learning over individual learning and the relative strength of their conformist social learning biases. Here we use both treatment effects and individual variation to test predictions about the impact of (1) the number of traits in an environment, (2) the adaptive or payoff relevance of those traits, (3) the fidelity of transmission, and (4) the size of groups. We find that both social learning and the strength of conformist transmission increases with the number of traits, the adaptive value of those traits, and the fidelity of transmission. The strength of conformist transmission increases with group size, but only when there were 2 traits in the environment. Using individual-level variation and recognizing that treatment effects predictably impact individuals differently, we show that IQ negatively predicts social learning, but has a U-shaped relationship to conformist transmission, suggesting strategic use of conformist-biased social learning among those with the highest IQ. Other plausible predictors, such as status, cultural background, and personality, were not predictive. Broadly, our results reveal that not only is the conformist transmission bias ubiquitous, but that past experiments, both human and non-human, have likely underestimated its prevalence and the prevalence of social learning by restricting designs to only 2 traits.

Humans are characterized by an extreme dependence on culturally transmitted information and recent formal theory predicts that natural selection should favor adaptive learning strategies that facilitate effective copying and decision making. One strategy that has attracted particular attention is conformist transmission, defined as the disproportionately likely adoption of the most common variant. Conformity has historically been emphasized as significant in the social psychology literature, and recently there have also been reports of conformist behavior in non-human animals. However, mathematical analyses differ in how important and widespread they expect conformity to be, and relevant experimental work is scarce, and generates findings that are both mutually contradictory and inconsistent with the predictions of the models. We review the relevant literature considering the causation, function, history, and ontogeny of conformity, and describe a computer-based experiment on human subjects that we carried out in order to resolve ambiguities. We found that only when many demonstrators were available and subjects were uncertain was subject behavior conformist. A further analysis found that the underlying response to social information alone was generally conformist. Thus, our data are consistent with a conformist use of social information, but as subjects’ behavior is the result of both social and asocial influences, the resultant behavior may not be conformist. We end by relating these findings to an embryonic cognitive neuroscience literature that has recently begun to explore the neural bases of social learning. Here conformist transmission may be a particularly useful case study, not only because there are well-defined and tractable opportunities to characterize the biological underpinnings of this form of social learning, but also because early findings imply that humans may possess specific cognitive adaptations for effective social learning.

Human culture relies on extensive use of social transmission, which must be integrated with independently acquired (i.e. asocial) information for effective decision‐making. Formal evolutionary theory predicts that natural selection should favor adaptive learning strategies, including a bias to copy when uncertain, and a bias to disproportionately copy the majority (known as ‘conformist transmission’). Although the function and causation of these evolved strategies has been comparatively well studied, little is known of their development. We experimentally investigated the development of the bias to copy‐when‐uncertain and conformist transmission in children from the ages of 3 to 7, testing predictions derived from theoretical models. Children first attempted to solve a binary‐choice quantity discrimination task themselves using asocial information, but were then given the decisions of informants, and an opportunity to revise their answer. We investigated whether children's revised judgments were adaptively contingent on (i) the difficulty of the trial and (ii) the degree of consensus amongst informants. As predicted, older but not younger children copied others more on more difficult trials than on easier trials, even though older children also showed a tendency to stick with their initial, asocial decision. We also found that older children, like adults, were disproportionately receptive to non‐total majorities (i.e. were conformist) whereas younger children were receptive only to total (i.e. unanimous) majorities. We conclude that, whilst the mechanism for incorporating social information into decision‐making is initially very blunt, across the course of early childhood it converges on the adaptive learning mechanisms observed in adults and predicted by cultural evolutionary theory. A video abstract of this article can be viewed at http://youtu.be/Qb6JINGYqVk

Interest exists in assessing health-related quality of life as one aspect of treatment effectiveness with substance abuse clients. The SF-36 Health Survey is a self-report measure assessing subjective health status along physical and mental health dimensions. Subjects were 252 adults in an outpatient, randomized clinical trial for substance abuse treatment. Subjects reported significantly more impairments in functioning when compared to U.S. population norms, but differences disappeared after three months of treatment. There was little support that quality of life functioning was significantly related to substance use during treatment. Results highlight the importance of using the SF-36 to facilitate treatment planning.

AcknowledgementsWe are grateful to Alex Mesoudi, Volker Franz and two anonymous reviewers for comments on the manuscript. The research was supported in part by an ERC Advanced Grant (EVOCULTURE, Ref. 232823) awarded to KNL.Sex differences in confidence and conformity 2 AbstractLack of confidence in one's own ability can increase the likelihood of relying on social information.Sex differences in confidence have been extensively investigated in cognitive tasks, but implications for conformity have not been directly tested. Here, we tested the hypothesis that, in a task that shows sex differences in confidence, an indirect effect of sex on social information use will also be evident. Participants (N=168) were administered a mental rotation (MR) task or a letter transformation (LT) task. After providing an answer, participants reported their confidence before seeing the responses of demonstrators and being allowed to change their initial answer. In the MR, but not the LT, task, women showed lower levels of confidence than men, and confidence mediated an indirect effect of sex on the likelihood of switching answers. These results provide novel, experimental evidence that confidence is a general explanatory mechanism underpinning susceptibility to social influences. Our results have implications for the interpretation of the wider literature on sex differences in conformity.Sex differences in confidence and conformity 3