In the target article, Bard, Keller, and Leavens call us to increase inclusivity in developmental research through going Worldwide, In situ, Local, and Diverse (WILD) (Newson et al., Reference Newson, Buhrmester, Xygalatas and Whitehouse2021). A key part of this argument is that beyond the need for diversity in the participants and samples used (Nielsen et al., Reference Nielsen, Haun, Kärtner and Legare2017), the theories themselves will be affected if a WEIRD bias is carried over. This bias is inevitably present in the participant samples – not only from specific nations but also from specific ethnicities, ages, and socioeconomic statuses – but it is also in the common sense of theorists and researchers shaping what is imaginable and how data is interpreted. We wholeheartedly agree that centring inclusivity and diversity is a key direction in developmental science and, in particular, strongly echo the authors’ call for rethinking our developmental theories. Here, we argue that just as developmental psychologists have sought developmental origins of behaviour, so similarly we must seek – and be honest about – the origins of our theories. We highlight below the pitfalls of developmental theories built on unexamined cultural biases.

In developmental science, there has sometimes been a tension between theories intended to be universal and a need to understand the role of culture and the environment in development. While there are aspects of child development in which culture may play only a very limited role (e.g. Futagi, Toribe, & Suzuki, Reference Futagi, Toribe and Suzuki2012), for most of our developmental theories, when carefully examined, this is not the case. In Figure 1, we demonstrate how developmental theory is often conceptualised with respect to culture: here, there is an underlying “true” developmental trajectory, upon which the variability due to (stemming from) cultural contexts is added like icing on a cake. The resulting measurement taken by researchers is then the combination of the underlying developmental pattern and the cultural context.

Figure 1.

One common implicit conceptualisation of the role of culture in developmental theory. The theorised underlying pattern passes through different theorised cultural contexts before being measured in each culture. In extreme examples there can be complete confounding between the cultural context of the experimenter and the theorised underlying pattern.

There are multiple challenges with a developmental theory conceptually similar to that illustrated in Figure 1. First, careful examination of many (though not all) developmental phenomena demonstrates that there is no divorcing development from context (Forbes, Aneja, & Guest, Reference Forbes, Aneja and Guest2024; Kline, Shamsudheen, & Broesch, Reference Kline, Shamsudheen and Broesch2018). To take one of the examples raised by Bard et al., attachment cannot occur in a vacuum; rather, it is enmeshed in cultural caregiving and communal practices. The same is true for many theories: what is measured is not an accident of cultural context confounding the universal trend, but the reality of development within that context.

This problem is exacerbated when considering the culture and (unconscious) bias of the researchers themselves (Fish, Reference Fish2022; Syed & Kathawalla, Reference Syed, Kathawalla and McLean2022). Building a theory based on observations from one or several similar cultures can lead to the assumption that the theorised underlying developmental pattern is what is observed in the culture with which the authors are most familiar. Combining this with the dominant WEIRD-centric approach to psychology (Nielsen et al., Reference Nielsen, Haun, Kärtner and Legare2017) can lead even to the position that “normal” development happens in these cultures, rather than recognising that the observed phenomenon is as shaped by culture and society there as anywhere else. As a counterfactual, a theory that instead started from observations of development across many cultures and contexts (and where relevant, species), before positing mechanisms based on shared commonalities across contexts, is far less likely to fall into this trap.

A final step can sometimes occur wherein the theory then becomes constraining to the data being collected, and therefore to our understanding of development. A theory developed on the ideal rather than on observation of a universal then constrains the questions that are asked and the contexts in which data are collected. If the dominant theory suggests that a certain behaviour is universal, then it may not be examined across contexts, even though the universality is predicated on observations in only one other, unrelated context. This is why, as Bard et al suggest, this should either be adjusted for other cultures or the dominant theory needs to be presented as being bound by culture.

In developing good theories for developmental science, we must be honest about our metaphysical commitment, among other factors (Guest, Reference Guest2024). The metaphysical commitment governs what is covered by the theory and what is instead implicitly assumed but not under investigation. Often due to the contextual origin of the theory, the cultural biases implicit in its development go unexplored and untested. Instead, developmental science needs to consider the context not as a separate component that alters measurement of the underlying phenomenon, but as integral to child development. Failing to do this gives us theories with weak explanatory power, as they describe development well in one context, but poorly across a range of contexts.

The proposal by Bard et al. is not purely about inclusivity for its own end, though on its own this would be welcome due to the need for diverse participants and researchers. Instead, the steps outlined by Bard and colleagues grant us practical solutions for developing theories with greater epistemic power, because they can successfully account for and integrate data from across diverse cultures. Crucially, the Five Steps proposed start with observing to avoid imposing biased constructs, understanding local pathways to appreciate diversity, building inclusive definitions that can travel across contexts, and then testing for broader principles. This process forces researchers to confront their own hidden assumptions, leading to theories that are both more grounded in observable truths of development and are explicit about cultural context in their metaphysical commitments.

We echo the authors’ call to go WILD, especially regarding our developmental theories. Here, we do not argue necessarily that all research should be cross-cultural or that theories must avoid universals. Instead, we build on Bard et al. suggested course of action to encourage a careful re-examination of our developmental theories, especially with regard to their origin and the metaphysical commitments surrounding culture and context. Starting from a theoretical premise of universality due to unexamined origins might not just skew our understanding of development but also cause us to miss the drivers and patterns of development themselves.