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The Cog in the Ratchet: Illuminating the Cognitive Mechanisms Generating Human Cumulative Culture

Periodic Reporting for period 3 - RATCHETCOG (The Cog in the Ratchet: Illuminating the Cognitive Mechanisms Generating Human Cumulative Culture)

Reporting period: 2018-09-01 to 2020-02-29

In human populations, skills and knowledge accumulate over generations, giving rise to behaviours and technologies far more complex than any single individual could achieve alone. This ratchet-like property of human culture appears absent in nonhuman species, as socially transmitted behaviours in animal populations are generally no more complex than those that can be acquired by trial and error. Scientists from a wide range of disciplines have offered high-profile speculative theories about the underlying differences that might be responsible for this striking evolutionary discontinuity, but adequate empirical evidence is still lacking. In the RATCHETCOG project, we aim to implement a comprehensive systematic investigation into cumulative cultural evolution, using experimental methods that offer sufficient flexibility to generate valid comparisons across three critical research domains: species differences across the primate family tree; age differences over human development; and learning condition differences in groups of adult human participants. The methods that we have devised within the project have allowed us to both measure and manipulate the complexity of transmitted behaviours, and as such they provide a tool for analysing the extent of ratcheting under different conditions and across different populations. Each of the three research strands provides a vital source of evidence. Studies of nonhuman primates will reveal the limits on learning in these species, and studies with children will provide key opportunities to determine which cognitive abilities predict the development of capacities for cumulative culture. Finally, comparing different learning conditions in groups of adults is critical, as these experiments will allow clear causal conclusions regarding prerequisites and constraints, in relation to task complexity. The project will therefore fully expose the cognitive machinery responsible for the uniqueness of human culture.
The current report covers the first 30 month period of a five-year project, and therefore reflects our interim progress towards the overall goals of the project. Two of the research team members were appointed in the first month of the project, and the remaining four joined in October 2016 (month 14), so much of the planned data collection began in earnest midway through the current reporting period, following on from development and pilot work that was completed in the first year. During this period we have made considerable progress towards realising the objectives outlined in the proposal. The work performed during the period covered by this report has been summarised below, in relation to the stated objectives of the original proposal and grant agreement.


Work Package 1: Task Development

In the research proposal it was stated that, “A task will be developed which can be used to study the potential for ratcheting in the social learning of members of diverse populations, including children of varying ages, and primates of different species, as well as adult humans”.

The project involves developing a novel method for assessing the potential for cumulative culture by testing how effectively learners can make use of information that has been acquired vicariously. Specifically, our methods are intended to evaluate whether individual participants’ performances suggest that repeated social transmission could generate behaviour that is increasingly advantageous in terms of the resulting payoffs. In addition, the methods can assess whether payoff increases actually do occur under real conditions of social transmission (in human adults). We have achieved this objective, and (as per the proposal) we have developed both computer-based, and physical stimuli equivalent, versions of the experimental task. So far we have used these tasks to test hypotheses about the necessary conditions for cumulative culture in young children (see WP2 and WP3 progress below) and in human adults (see WP4 and WP5 progress below). We have also shown that capuchin monkeys can be trained to a learning criterion indicative of basic competence in relation to the demands of the task (see WP6 progress), and work is now under way to investigate whether the performance of task-competent individuals could potentially generate a ratchet effect (also detailed under WP6), and how their performance corresponds to that of human children (see WP7 progress).


Work Package 2: Testing ontogenetic development of capacities for cumulative culture in human children

In the research proposal it was stated that, “Studies with young children of a range of ages (18 months to 6 years old) will establish at what age ratcheting over learner generations becomes possible in young children”.

As noted above, we have already embarked on data collection with human children using our experimental task. Our first study (manuscript currently in preparation) focussed on children’s performance following observation or personal experience of a simple binary choice. This was an important starting point to help us to understand whether there were differences in the extent to which children were able to learn from observation of another’s experience, compared with learning from their own. Broadly speaking, children were able to use the social information as effectively as information gleaned from their own personal choices and experience, and both abilities improved with age. In terms of dissemination activity (please see table of activities) this work was presented at the 2016 Culture Conference in Birmingham (June 2016) by Renner, and at the New Directions in the Evolutionary Social Sciences workshop in Cambridge (December 2016) by Caldwell, and also at the BCCCD meeting in Budapest (January 2017) by Renner. Over and above what was planned in the original proposal, we also formed a new collaborative link with researchers from Peking University in Beijing, China, which allowed
Understanding differences between nonhuman learning and traditions and human cumulative cultural evolution (CCE) continues to be an extremely hot topic, and recent demonstrations of CCE-like effects in nonhumans have generated great interest (e.g. Claidiere et al., 2014, Proc Roy Soc B; Sasaki & Biro, 2017, Nature Comms). However, to our knowledge we remain the only group developing flexible methods for studying cumulative culture which will allow us to directly manipulate variables such as the complexity and opacity of the transmitted traits, whilst holding other aspects of the task structure constant. This will permit a much fuller understanding of the mechanisms required to transmit cumulative cultural traits, and the extent to which we can observe similar phenomena in nonhumans. We therefore expect that the findings from this project will have substantial impact across multiple academic disciplines (including Anthropology and Zoology, as well as Psychology).