Boyer suggests that two simple cognitive systems – acquisitiveness and cooperation – might be used in combination to explain humans’ rich and varied intuitions about ownership and property. The two main arguments in favor of the minimalist model articulated by Boyer are that the model is parsimonious and that these two systems can be used to explain human intuitions about ownership. At face value, the first argument is clearly supported. Boyer's model is far simpler and more specific than previous proposals, including the Naïve Theory of Ownership proposed by Nancekivell, Friedman, and Gelman (Reference Nancekivell, Friedman and Gelman2019). The characteristic of Boyer's model that allows it to be so lean and efficient is that it situates ownership judgments as a process of navigating relationships between agents, setting aside other considerations. The idea that concepts of ownership and property are really about the relationships between people is not new, but the minimalist model takes the idea to its logical extreme. This formulation respects the ubiquity, universality, and salience of ownership concepts while attempting to explain ownership psychology as simply as possible.

In contrast, it is unclear whether the second argument – that the minimalist model can explain ownership intuitions – is fully supported. In principle, the minimalist model can be effectively mapped onto the early emergence of ownership psychology, and it can explain ownership intuitions that are simple (e.g., identifying property and owners) and complex (e.g., intuitions about property creation, humor, and morality). However, two important findings that may be difficult for the minimalist model to explain are downplayed in the current proposal. The first is that mature intuitions about property exchanges develop over a relatively extended period of time, and the second is that concepts of ownership incorporate notions of object history. Each of these findings is addressed very briefly in the target article, but the scope and effectiveness of the proposed model are difficult to evaluate without more specific information about how the model addresses them.

Although much of the target article's focus is on the early emerging and ubiquitous nature of ownership psychology, Boyer briefly notes that adult-like intuitions about property exchanges take time to develop, suggesting that “children's apparent confusion simply means that they have not acquired a full data-base for the consequences of giving in different contexts” (target article, sect. 10.1.1). This conclusion is misaligned with findings in the literature. Friedman and Neary (Reference Friedman and Neary2008) found that children exhibited a “first possessor bias,” a tendency to conserve ownership with an initial owner, in every scenario except when objects were giftwrapped and described as “a present.” Noles and Keil (Reference Noles and Keil2019) found that this bias persisted until at least age 9, but at the same time, even children as young as 4 exhibit adult-like intuitions when making judgments about other interactions with property (e.g., see Nancekivell, Davidson, Noles, & Gelman, Reference Nancekivell, Davidson, Noles and Gelman2023). Similar findings have been reported with respect to children's intuitions about property rights (Kim & Kalish, Reference Kim and Kalish2009). It is unclear why some aspects of ownership psychology, specifically those most germane to acquisition, take so long to develop while other complex intuitions about ownership appear early in development and change very little. Simply suggesting that children need more time and experience fails to reconcile the minimalist model with the long and nuanced development of some, but not all, of children's intuitions about ownership.

The second finding that is not fully addressed in Boyer's proposal is the observation that concepts of ownership incorporate notions of object history that extend beyond the features, affordances, and value of objects. In the target article, section 7.4 addresses the idea that representations “inherit information” about interactions with people and property, but the brevity and vagueness of this premise fail to capture the centrality of object history to ownership psychology. The special attention that people pay to object history is apparent in diverse phenomena. Toddlers spontaneously connect owners to property and use spatiotemporal cues to monitor ownership when owned objects are identical (Gelman, Manczak, & Noles, Reference Gelman, Manczak and Noles2012; Hood & Bloom, Reference Hood and Bloom2008), and absent spatiotemporal cues, children and adults will search for traces of object history to guide their ownership judgments (Gelman, Manczak, Was, & Noles, Reference Gelman, Manczak, Was and Noles2016). Young children and adults treat property as nonfungible (McEwan, Pesowski, & Friedman, Reference McEwan, Pesowski and Friedman2016), and they go to great lengths to avoid violating others’ property rights.

Object history also powerfully influences value judgments. Children and adults exhibit an endowment effect, wherein owned objects are judged to be more valuable than other objects, even if they are identical (Hood, Weltzien, Marsh, & Kanngiesser, Reference Hood, Weltzien, Marsh and & Kanngiesser2016). Children prefer “their” object and its associated history to newer, nicer items, and special histories affect the value of objects. For example, possession by a famous figure enhances an object's value (Gelman, Frazier, Noles, Manczak, & Stilwell, Reference Gelman, Frazier, Noles, Manczak and Stilwell2015) and association with a despised celebrity diminishes an object's value (Newman, Diesendruck, & Bloom, Reference Newman, Diesendruck and Bloom2011). History also influences moral judgments: Young children judge that it is wrong for items to be switched between owners, even if the items are identical and the owners are unaware of the substitution (Nancekivell et al., Reference Nancekivell, Davidson, Noles and Gelman2023).

Although there are many studies of ownership psychology, there are relatively few detailed theories about what ownership actually is. The minimalist model proposed by Boyer is interesting and more parsimonious than the Naïve Theory of Ownership proposed by Nancekivell et al. (Reference Nancekivell, Friedman and Gelman2019), but does this simplicity come at the cost of explanatory power? It is unclear whether the two simple systems that make up this model are sufficient to both explain the nuanced development of ownership concepts and to account for the prominent influence that history has on ownership psychology.