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ERC

RATCHETCOG Report Summary

Project ID: 648841
Funded under: H2020-EU.1.1.

Periodic Reporting for period 1 - RATCHETCOG (The Cog in the Ratchet: Illuminating the Cognitive Mechanisms Generating Human Cumulative Culture)

Reporting period: 2015-09-01 to 2017-02-28

Summary of the context and overall objectives of the project

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.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The current report covers the first 18 month period of a five-year project, and therefore we are still at an early stage in the life 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 has only recently begun in earnest, following on from development and pilot work that was completed in the first year. Nonetheless, 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”.

This objective has been achieved, and (also as per the proposal) we have developed both computer-based, and physical stimuli equivalent, versions of the experimental task. We have so far used the task in data collection with human children (using both a computer-based stimulus-selection version and a physical object-choice version), and with nonhuman primates (squirrel monkeys also tested using a computer-based stimulus-selection version and a physical object-choice version, and capuchin monkeys tested using the computer-based version). We have also developed a more complex computer-based version of the task for our studies with adult humans, and used this to collect pilot data. As planned, one of the postdoctoral research assistants has taken primary responsibility for coding of computer-based experimental methods.


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. One study (now complete) 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 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. Over and above what was planned in the original proposal, we have also formed a new collaborative link with researchers from Peking University in Beijing, China to obtain an equivalent cross-cultural dataset. This will allow us to determine the extent to which our findings are generalizable to another population from a very different cultural environment. Ongoing data collection with nonhuman primates – see WP6 – will permit species comparisons, which will allow us to determine whether any aspects of performance on this task appear to distinguish humans from nonhuman primates. One of the PhD students who joined the project in October 2016 has now also embarked on data collection looking at the development of capacities for cumulative culture using our reward-accumulation version of the stimulus selection task (i.e. involving multiple stimuli, and multiple selections, generating a continuum of performance success). We are collaborating on this work with a colleague who specialises in research on children’s cognitive development.


Work Package 3: Testing effects of complexity of social information on children’s capacity for cumulative culture

In the research proposal it was stated that, “The performances of human children will also be compared across age groups in which potential for ratcheting can be established (Objective 2), using social demonstrations of varying complexity.”

As is clear from the above extract, this particular objective represents work that will build on findings generated as part of WP2, described earlier. The necessary groundwork from WP2 will establish how we can identify a ratchet-like effect in children’s learning using a highly transparent version of the task, and will determine the effect of age on performance. This work in currently ongoing, so we have yet to embark on investigating the research questions proposed within WP3.


Work Package 4: Investigating the relationship between transmission mechanisms and behavioural complexity in adult humans

In the research proposal it was stated that, “The project will also establish whether certain types of social information are critical for the transmission and/or ratcheting of certain types of behaviour.”

In relation to this objective, we currently have a manuscript under review which investigates the relationship between behavioural complexity and benefits gained from intentional teaching, compared with information about process of completion in the absence of active instruction from an experienced partner (Caldwell, Renner & Atkinson, under review). This study found that, in line with our predictions, intentional teaching particularly facilitated the transmission of hard-to-learn skills. We also published a review paper (Caldwell, Cornish & Kandler, 2016) discussing the relevance of different task goals in cultural evolution experiments, and the likely effects of different task goals on the behavioural forms that emerge through transmission. This led to the completion of an empirical student directly comparing the effects of transmission on behavioural forms depending on the goal of the task from the perspective of the participant. Our findings from this study (Atkinson, Renner & Caldwell, in preparation) yielded valuable insights into this issue and provided evidence consistent with the ideas proposed within the review article.


Work Package 5: Investigating the influence of adult human capacities for understanding others’ minds on cumulative culture

In the research proposal it was stated that, “Again using microsociety research designs, the project will also investigate the causal influence of theory of mind in generating the ratchet effect in cultural transmission.”

We have embarked on pilot work to establish how best to investigate this using our task software. Two of the PhD students who started in October 2016 have been planning studies related to this work package. One of these PhD students has been assigned a project topic looking at how adult-like inferences about others’ knowledge can contribute to the generation of a ratchet effect over transmission. The other PhD student has been assigned a project topic investigating the effect of explicit metacognition on cumulative culture. For both of these projects, pilot work has begun to develop appropriate methods.


Work Package 6: Investigating limits on ratcheting in the social learning of nonhuman primates

In the research proposal it was stated that, “Studies with primates (chimpanzees, capuchins and squirrel monkeys) using the experimental task, will establish whether ratcheting over learner generations is possible in nonhuman primates.”

We have completed our first study with nonhuman primates, testing squirrel monkeys using a computer touchscreen version of the task (starting with a simple binary choice version, analogous to the method used in our first study with children for WP2). Although we were able to collect data on task performance for thirteen individuals, only one reached the pre-determined performance criteria we had set as a means of determining whether they were task-proficient with respect to the reinforcement contingencies. This limited the extent that we could draw conclusions about nonhuman primate performance generally, and therefore also the extent to which we could make valid comparisons with human performance (see WP7, below). A follow-up study is currently underway which uses a three-dimensional version of the task (monkeys simply select one of two cups, one of which conceals a food reward). We suspect this version of the task may be more intuitive for the squirrel monkeys, but regardless of their overall success levels we anticipate being able to generate meaningful comparisons between their responses using the touchscreen vs. solid object versions of the task. It may or may not be possible to progress further with the squirrel monkeys in relation to establishing the potential for ratchet effects over transmission, as this would require evidence of basic task proficiency in relation to the potential value of social information. However, we have also commenced data collection with another of our intended species populations (capuchin monkeys). This began towards the end of the current reporting period (January 2017), starting with training individuals to interact with the computer touchscreen. One of the PhD students has been assigned a project topic focussing on the capacities of nonhuman primates, and she has taken responsibility for data collection with the capuchin monkeys.


Work Package 7: Comparing performances of children and nonhuman primates

In the research proposal it was stated that, “The performances of children and primates, using the same task, will also be explicitly compared to each other, in order to elucidate fundamental differences in how humans and nonhumans use social information.”

As noted above, in relation to WP6, we are not yet in a position to draw conclusions about species differences. However, so far the data that we have collected with populations of human children are in line with some of the expectations about human performance that were detailed in the original proposal. Whether this differentiates their performance from that of nonhuman primates remains to be seen. Our ongoing research with nonhuman primates (as detailed above in our progress report on WP6) will provide insights into this in due course.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

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). We have also already completed data collection on the first study that we know of which directly compares a replication goal with an external measure goal in a study of cultural evolution in adult humans. Since this study is likely to inform other researchers’ methodological decisions in future experimental work on cultural evolution, we expect this to generate a highly-cited publication.
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