Shedding light on the specificity of the evolutionary dynamics of peer cultures requires an examination of the selective pressures that shape their content. We suggest that drawing from theories of motivation may provide interesting insights about what makes those selective forces peculiar. Indeed, whether a cultural trait will propagate or decline crucially depends on whether individuals will invest their time and energy in learning, remembering, modifying, and transmitting it – that is, whether they will be motivated to do so.

Psychologists typically distinguish intrinsic motivation from extrinsic motivation (Ryan & Deci, Reference Ryan and Deci2000). Intrinsic motivation is defined as “the doing of an activity for its inherent satisfaction rather than for some separable consequence” (Ryan & Deci, Reference Ryan and Deci2000, p. 56). By contrast, extrinsically motivated behaviors are driven by the prospect of an external reward. In childhood, intrinsic motivation plays a major role in driving behavior. Indeed, as pointed out by the authors, children are cared for and provisioned by adults, thus reducing the necessity to engage in extrinsically motivated activities. In contrast, adults may have less time to allocate to intrinsically motivating activities. These differences may translate into different selective pressures on cultural traits: in peer cultures, the fitness of a cultural trait may depend more on its capacity to elicit intrinsic motivation, whereas in adult cultures, successful variants may be those that effectively serve an external goal (e.g., fulfilling physiological needs).

Understanding what shapes the evolutionary dynamics of peer cultures may thus require to describe which features of an activity make it intrinsically interesting. The literature on intrinsic motivation is rich in theories identifying such features (Ten, Oudeyer, & Moulin-Frier, Reference Ten, Oudeyer and Moulin-Frier2022). These include optimal incongruity (Dember & Earl, Reference Dember and Earl1957; Hunt, Reference Hunt1965), intermediate novelty (Berlyne, Reference Berlyne1960), optimal challenge (Csikszentmihalyi, Reference Csikszentmihalyi1990), or learning progress (Poli et al., Reference Poli, Meyer, Mars and Hunnius2022; Poli et al., Reference Poli, Meyer, Mars and Hunnius2025; Ten et al., Reference Ten, Kaushik, Oudeyer and Gottlieb2021). A common point of these theories is that they posit that intrinsic motivation is maximized when individuals find themselves in a sweet spot between the trivial and the impossible. Activities need to be challenging enough to prevent boredom, but not too challenging to avoid creating anxiety or discouragement (Csikszentmihalyi, Reference Csikszentmihalyi1990). This predicts that the evolutionary dynamics in intrinsically motivated populations would differ markedly from those in extrinsically motivated ones. Among intrinsically motivated individuals, cultural packages are expected to include traits that offer an optimal level of challenge. In contrast, among extrinsically motivated individuals, cultural packages are likely to consist of traits that become increasingly efficient at fulfilling their specific function.

A second key difference between extrinsic and intrinsic selective pressures is that the latter depend on the current knowledge of group members. Extrinsically motivated individuals should always select the most efficient cultural trait, regardless of their current knowledge. In contrast, the intrinsic value of an activity depends on the current skills of the individual: for instance, a chess puzzle that is engaging for a beginner will be boring for an advanced player. As a result, while incentives shaped by extrinsic pressures remain stable, intrinsic selective pressures produce shifting incentives that evolve with the individual’s skill level, rendering the cultural fitness landscape more dynamic over time. This could for instance explain the observation reported by the authors that popular games often become increasingly complex, while games in decline become simpler. Indeed, as a game gets more popular, children may be more familiar with the rules and strategies, thus reducing how challenging the game is. To remain within the sweet spot of optimal difficulty, the game may thus need to become more complex.

That peer cultures are directed toward moving targets may be central to explaining their contribution to cultural adaptation. By steering evolution toward what is unknown, yet learnable, intrinsic selective pressures may allow peer cultures to follow gradients of increasing complexity, even if those are not associated with any external utility. Eventually, this repertoire of complex skills and knowledge may be useful for achieving an external goal, at which point it could be exapted for extrinsic purposes. This is one possible interpretation of the case study of Matsé children reported by the authors: their proficiency at fishing may have originated in a curiosity for discovering river areas. Over time, this curiosity would have led them to build an increasingly complex repertoire of river-related skills, ultimately allowing them to exploit it for foraging.

It is worth emphasizing that adults also engage in curiosity-driven activities and, for example, have been shown to track their own learning progress when choosing tasks (Ten et al., Reference Ten, Kaushik, Oudeyer and Gottlieb2021). This suggests that studying peer cultures can illuminate evolutionary forces that are also at play in adult culture but are often overlooked. Indeed, much of the current research on cultural evolution assumes an external objective, such as in models implementing payoff-biased social learning (Henrich, Reference Henrich2004; Kendal et al., Reference Kendal, Boogert, Rendell, Laland, Webster and Jones2018) or in experiments where participants are incentivized to maximize their score (Caldwell & Millen, Reference Caldwell and Millen2009; Derex et al., Reference Derex, Bonnefon, Boyd and Mesoudi2019). As a result, our understanding of cultural evolution is heavily skewed toward scenarios where extrinsic motivation drives the evolution of cultural traits. Recognizing the role of intrinsic motivation could help generate more nuanced predictions about cultural dynamics in both peer and adult contexts. For instance, cultural traits shaped by extrinsic selective pressures may be tightly constrained by functional requirements, whereas those shaped by intrinsic motivation may exhibit greater variability. This pattern may be reflected in a recent ethnographic study (Kaaronen et al., Reference Kaaronen, Henrich, Manninen, Walsh, Wisher, Eronen and Riede2025) comparing knots and string figures, which suggests that “the state space of string figures (Kaaronen et al., Reference Kaaronen, Walsh, Henrich, Wisher, Miu, Manninen, Eronen and Riede2024), a common game or pastime across cultures worldwide, seems to have been explored much more thoroughly and creatively than that of knots.” This illustrates how the design space of cultural traits can be explored independently of extrinsic utility, a process that may be key to understanding the open-ended nature of human cultural evolution.

Overall, we believe that a comprehensive understanding of cultural dynamics requires a clearer specification of the mechanisms underlying intrinsically motivated exploration. Studying peer cultures offers a promising path toward this goal and may illuminate important, yet overlooked, evolutionary forces. However, as the vast majority of research on intrinsic motivation has been conducted with Western participants, and largely outside the context of cultural evolution, further work is needed to build a more complete and cross-culturally valid picture of motivational mechanisms.