We developed a novel method (WP1) for experimental testing of capacities for cumulative culture (described in Caldwell et al., 2020, WIRES Cogn Sci). This method used a stimulus selection paradigm which we first validated using straightforward comparisons of the use of information acquired vicariously, versus through one’s own activity. This included a cross-cultural study of human children, (WP2: Atkinson et al., 2020, J Exp Psychol Gen) and studies with nonhuman primates (WPs 6&7: Renner et al., 2019, PeerJ; Renner et al., 2021, Sci Rep). We further developed this task to investigate the developmental progression of children’s capacity for cumulative culture (WP2), finding that children as young as 3 years can learn from a social demonstration in a manner that would support the accumulation of beneficial modifications, as long as there was no memory load. However, when memory was required, only older children (5-6 years) derived greater benefit from high-scoring, compared with low-scoring, demonstrations. This showed that the expression of cumulative culture depended on both the cognitive capacities of the learners and the specific demands of the task (reported in Wilks et al., 2021, J Exp Child Psychol). In further studies of human children we investigated other cognitive demands likely to be implicated in many real world cases of cumulative culture (WP3). These included studies in which participants were required to: make inferences based on others’ reactions along with a knowledge of their goals (Blakey et al., revision under review, J Exp Child Psychol); understand others’ visual perspective (Blakey et al., revision under review, J Comp Psychol); and direct their learning towards those who possessed relevant information (Blakey et al., 2020, PsychArXiv). In all cases we found that these demands placed significant constraints on the use of social information by very young children (e.g. under 5 years). We used further variations of our stimulus selection task to study potential constraints on cultural transmission in adult human social learning (WPs 4&5). We found that under certain conditions, intentional knowledge transmission by cultural parents strongly facilitated the accumulation of beneficial information in chains of adult learners (Mackintosh et al., in prep). In contrast, we found little evidence to suggest that learners make inferences about others’ past behaviour, even when accurate inferences were theoretically possible and could boost performance (Atkinson et al., 2020, Cogn Sci). Finally, we found some suggestion of a possible role for “System 2” cognition in facilitating selective social learning in human adult participants (Dunstone et al., 2021, PloS One). In studies with nonhuman primates (WPs 6&7) we found that baboons and capuchin monkeys were, like very young children, in principle capable of learning from vicarious information in a manner which would lead to the accumulation of beneficial modifications over cultural transmission (Kean et al., in prep). However, it is likely that the conducive learning conditions required would rarely be encountered in the real world, and that the accumulation of benefits would only occur over a very limited number of generations of transmission. Overall we conclude from the findings of the project that there is no single factor precluding cumulative culture in nonhuman species. Rather, a wide variety of cognitive challenges are associated with the use of social information in most real-world cases of cumulative culture, and it is these (largely context-specific) challenges which constrain the expression of cumulative culture in other species.
