Boyer's computational model of ownership integrates a wide array of evidence and will generate fruitful discussions and research. However, clarification is needed to explain a key feature of human ownership: Respect for others’ property. In the minimalist model, B's respect for A's property is defined in terms of the cooperative system, and respect can vary based on the strength of A's affiliation with B's cooperative community. The set of representations defined in hypotheses 2–4 describe how the representation for B's respect for A's property can be extended to a third party C and to a default assumption of respect for the property of all within the cooperative sphere. While this describes a mature state of the psychology of ownership, consideration of how these representations develop can help to elucidate the model.

Children are not born respecting the property of others. In the first two years of life, toddlers frequently grab toys from peers leading to conflicts (Chen, Fein, Killen, & Tam, Reference Chen, Fein, Killen and Tam2001; Hay et al., Reference Hay, Paine, Perra, Cook, Hashmi, Robinson and Slade2021; Licht, Simoni, & Perrig-Chiello, Reference Licht, Simoni and Perrig-Chiello2008). By about 3 years of age, children will defend another person's property, suggesting a third-party representation of respect for others’ property (Rossano, Rakoczy, & Tomasello, Reference Rossano, Rakoczy and Tomasello2011). However, observational studies conducted in daycares, preschools, and elementary schools have found that conflicts over property continue into middle childhood (Bakeman & Brownlee, Reference Bakeman, Brownlee, Rubin and Ross1982; Putallaz & Sheppard, Reference Putallaz and Sheppard1990; Shantz, Reference Shantz1987). Given that children as young as 3 years of age will enforce respect of property for others, why do they, and older children, fail to respect property themselves?

This developmental pattern has implications for the relations between the representations in Boyer's model. According to the minimalist model, the dyadic representations of hypothesis 2 provide a foundation for the more complex third party (hypothesis 3) and default (hypothesis 4) representations. In other words, children should respect the property of A before they defend the property of A from third parties. However, given the evidence above, this order of development is actually reversed. This raises the question of where the third-party representation comes from and how the gap between what one should do and what one does closes with age. In this commentary, I will focus only on the second issue and consider three possible explanations.

First, it is possible that children are only dis-respecting the property of peers who are not in their cooperative network. In terms of the minimalist model, a certain agent A may have a lesser status in the cooperative network, relative to agent B, such that Min(A) < Min(B). The lower status of A would make them more susceptible to disrespect than B. While plausible, this seems unlikely given that, in the first 2 years, children both take from and give to the same peers when observed over time (Chen et al., Reference Chen, Fein, Killen and Tam2001; Hay et al., Reference Hay, Paine, Perra, Cook, Hashmi, Robinson and Slade2021). However, it is possible that as affiliative groups become more clearly defined with age, children begin to treat those on the fringes of the cooperative network differently.

An alternative explanation is that children may perceive other children's ownership claims as having less strength than their own claims. Evidence for this possibility comes from research in which children are given an option to take resources from others. For example, when 4–7-year-olds were told that they could take objects that had been made (stronger claim) or found (weaker claim) by another child, they took more of the found objects, seemingly respecting a stronger claim for the made objects (Davoodi, Nelson, & Blake, Reference Davoodi, Nelson and Blake2020). Other studies have found variation in respect based on strength of claim for younger children (Pesowski, Kanngiesser, & Friedman, Reference Pesowski, Kanngiesser and Friedman2019). Although there is limited evidence for this possibility thus far, it would fit with Boyer's model by varying the “s” term for self and other.

A third explanation for children's lack of respect for ownership implicates a more general pattern of development that applies across the domain of moral cognition. Put simply, children recognize moral transgressions among third-party actions before they follow those moral norms themselves. One well-replicated case concerns norms for the fair distribution of resources. When 3-year-olds are asked how many stickers they should share with a peer, they typically say half. However, when given a chance to share with a peer in the exact same situation, they keep more for themselves (Smith, Blake, & Harris, Reference Smith, Blake and Harris2013). The so-called knowledge behavior gap takes several years to close at which point children give what they know they should (Blake, McAuliffe, & Warneken, Reference Blake, McAuliffe and Warneken2014), but some studies suggest that the gap continues into adulthood (Keller, Gummerum, Canz, Gigerenzer, & Takezawa, Reference Keller, Gummerum, Canz, Gigerenzer and Takezawa2013). Multiple, general developmental processes may facilitate the alignment of behavior with normative beliefs, including, for example, behavioral control (Steinbeis & Over, Reference Steinbeis and Over2017). However, it is also possible that the underlying representations for first-person behavior and third-party norms remain distinct. If this is the case for ownership, then the minimalist model may need to be adapted to account for when and how first-person respect for others’ property connects with the representations for respect among third parties.

In summary, the development of children's respect for other's property offers a key case for understanding the relations among the components of the minimal model. I believe that this case presents an opportunity to test specific elements of this new theory and refine our understanding of how children attain the mature psychology of ownership.