Bard, Keller, and Leavens propose a WILD (Worldwide, In situ, Local, and Diverse) framework that challenges the still pervasive WEIRD (Western, Educated, Industrialized, Rich, and Democratic) bias underpinning much of the foundational data and the theoretical assumptions of the discipline (Henrich, Heine, & Norenzayan, Reference Henrich, Heine and Norenzayan2010). We strongly support the WILD framework and the usage of data from traditional, small-scale societies as well as cross-species comparisons to demonstrate the theoretical limitations of past developmental theories. We propose to extend the WILD framework to encompass a critical but underrepresented group: non-WEIRD societies undergoing rapid industrialization and globalization (SIG). Using Attachment Theory (AT), we demonstrate that studying SIG provides a unique and powerful theoretical stress test, exposing the limits of WEIRD-centric assumptions and yielding essential insights for developing inclusive and context-sensitive theories of human development.

Primarily concentrated in East Asia, South/Southeast Asia, and Latin America, SIG is home to approximately 1.6 billion children – over 70% of the global child population (United Nations, 2022). They exist at a complex juncture, simultaneously driven by global economic structures and colonial legacies while retaining distinct local cultural practices and institutions. As discussed in Bard et al., small-scale societies expose the roots of human psychological variation, often showing ancestral caregiving systems that predate the WEIRD individualistic family structure. By contrast, SIG exposes the functional plasticity of the human developmental system under conditions of contemporary, rapid socioecological change. This plasticity results from a paradox of modernity: economic demands (e.g., urbanization, transnational labor migration) forcing non-WEIRD cultures to adapt their caregiving structures while retaining long-standing non-WEIRD cultural values (e.g., collectivism, filial piety).

Living with this paradox is a stable reality for billions of people, and therefore, theories built on SIG data are likely to apply to the majority of the world. Moreover, this context forces developmental scientists to address the question of mechanism: if a theory posits a universal developmental pathway but a non-WEIRD industrialized context achieves the same outcome via a different, complex caregiving configuration, the universality is not in the pathway but perhaps in the intentions or functions behind caregiving practices across cultures – a crucial and fundamental theoretical advance for the WILD agenda.

Classical formulations of AT (Ainsworth et al., Reference Ainsworth, Blehar, Waters and Wall1978; Bowlby, Reference Bowlby1969) rest on two core – and often implicit – assumptions: (1) attachment formation is primarily a dyadic relationship between the caregiver and the child, and (2) the attachment figure is kin-based, typically the biological mother or father. The SIG caregiving ecology systematically challenges both these assumptions while still maintaining robust developmental outcomes in two key ways.

First, in SIG contexts characterized by collectivism and interdependence, caregiving responsibilities are typically distributed across multiple family members rather than concentrated within a single dyad. Multi-generational households remain normative, with caregiving shared among parents, grandparents, and other extended kin. These arrangements reflect enduring cultural values – such as filial piety in East Asia (Zhou, Kan, & He, Reference Zhou, Kan and He2022), filial reciprocity in South Asia (Gupta & Sengupta, Reference Gupta and Sengupta2025), and familismo (family loyalty) in Latin America (Mutchler & Velasco Roldán, Reference Mutchler and Velasco Roldán2023) – and are amplified by economic pressures, such as dual-income demands and migration, enabling families to adapt while preserving their cultural continuity.

Empirical studies find that children in multi-generation households often form secure attachments not only to their parents but also to their grandparents (Blake et al., Reference Blake, Infurna, Castro, Webster, Dolbin-MacNab, Smith, Crowley and Musil2023; Xing et al., Reference Xing, Liang, Yue and Wang2016). This evidence directly challenges the necessity of a primary attachment figure. Instead, it supports a network model of attachment, in which multiple kin collaboratively co-construct a system of emotional security. The attachment system is not weakened by distribution but stabilized through cultural institutionalization; the security of the child depends on the reliability of the caregiving network, not the exclusivity of a dyadic bond.

Second, common caregiving practices in certain SIGs, such as Hong Kong (China) and Singapore, pose a particularly acute challenge to the kin-based assumption. These practices typically involve foreign domestic helpers (FDHs) – non-kin caregivers embedded within transnational labor systems. These FDHs live with the family in the household and provide the majority of physical and emotional childcare due to the long working hours of the parents (Ma, Chen, & Li, Reference Ma, Chen and Li2020; Sudo et al., Reference Sudo, Low, Kyeong, Meaney, Kee, Chen, Broekman, Nadarajan, Rifkin-Graboi, Tiemeier and Setoh2025). Empirical research shows that children frequently form secure attachments with their FDH caregivers (Kwok, Xie, & Kwan, Reference Kwok, Xie and Kwan2023), refuting the idea that attachment depends on biological relatedness. Instead, it affirms that the mechanism of attachment resides in the functional quality of caregiving, namely consistent, sensitive responsiveness (Ainsworth, Reference Ainsworth, Blehar, Waters and Wall1978). Notably, even though parents maintain their status as the “primary” caregiver (Ma et al., Reference Ma, Chen and Li2020), they often acknowledge and even value the emotional closeness between their children and the FDHs, reflecting the coexistence of enduring collectivist values (shared caregiving responsibility) and globalized individualist ideals (parental authorship of childcare).

The empirical reality of distributed care, involving extended kin and non-kin members, necessitates a shift from the dyadic focus of classic AT to a model that recognizes that security can be adaptively provided by a network. These complex caregiving ecologies may yield developmental outcomes that are more adaptive for an interconnected, globalized world. For instance, children who form intimate relationships with FDHs of different ethnicities exhibit lower intergroup biases toward other ethnic groups (Chen et al., Reference Chen, Corriveau, Lai, Poon and Gaither2018, Reference Chen, Ma, Groves and Gaither2025; Setoh et al., Reference Setoh, Sudo, Quinn and Lee2023). These findings suggest that the Internal Working Model (IWM) – the core representational mechanism in AT – is functionally plastic rather than fixed. Although the IWM universally organizes expectations about care and security, its content can be enriched through early experiences. When a primary attachment forms with a caregiver from a different cultural background, children internalize cross-group warmth and reliability, fostering more flexible and inclusive intergroup attitudes that, over time, reduce intergroup bias.

Together, the evidence reviewed provides a key missing link in the WILD agenda, demonstrating that developmental pathways are context-dependent and supporting a constructive evolutionary perspective. The SIG population thus concretizes Bard et al.’s call: by incorporating the developmental realities of the contemporary majority world, we can build a truly “worldwide” theory – one that grounds universal principles in demonstrated functional plasticity rather than presumed cultural necessity.