The evolutionary social sciences have long been concerned with the search for human universals, and questions surrounding them. Which traits, including psychological and behavioral traits, are part of our species-typical “human nature”? Are there any traits that are universally present in early childhood across cultures? Are there any traits that, barring developmental disability, develop reliably in all adults? Which traits that might be universal or widespread now can be linked to histories of natural selection acting in the past?

In this paper, we present new data bearing on debates about a possible domain of human universality: ownership, and the psychological and cultural norms and rules underlying it (Nancekivell, Friedman, & Gelman, 2019). The idea that ownership of some kind is a human universal is quite plausible, akin to claims that language, morality, and cooperation are part of human nature. But here the comparison to domains like language and morality is apt. Claims that humans everywhere make moral judgments, communicate linguistically, and regard some things as owned are much more general than claims about specific universals within those domains, such as specific grammatical or moral rules, which have proven to be much harder to find (Christiansen & Chater, 2009; Stich, 2006).

Here we examine a category of norms or rules of ownership that have been proposed as possible human universals, which we call first mover norms. First mover norms hold that an individual who acts first or with the greatest initial effort towards an ownable entity becomes socially recognized as the rightful owner of that entity. Psychologists have proposed and studied a variety of first mover norms including norms of first possession, first pursuit, effort, and creation or authorship. These can apply to both tangible items, such as human-made artifacts, natural resources, and land, as well as intangible items such as ideas and other forms of intellectual property (Friedman, 2010; Friedman & Neary, 2008; Friedman, Neary, Defeyter, & Malcolm, 2011; Li, Shaw, & Olson, 2013; Nancekivell et al., 2019). Using experimental tasks, developmental psychologists have shown that first mover intuitions typically develop in early to middle childhood in children in Canada, the U.S., and Europe (Friedman, 2008; Shaw, Li, & Olson, 2012; Verkuyten, Sierksma, & Thijs, 2015). A small cross-cultural literature using similar experimental tasks has supported these findings, albeit with some variation in developmental trajectory, providing evidence for potential universality of first mover norms (Kanngiesser et al., 2015; Kanngiesser, Itakura, & Hood, 2014; Kanngiesser, Rossano, & Tomasello, 2015; Rochat et al., 2014).

The ethnographic literature, on the other hand, provides mixed evidence for the universality of first-mover norms. First possessor rules of property ownership are known to exist in non-European legal systems, including Islamic, African, and Native American legal and informal traditions (Barnard & Woodburn, 1988; Gluckman, 2017; Lentz, 2006; Lueck, 1995). At the same time, the literature on property rights across the world and throughout history documents a multitude of cases where ownership rights are communal, partial, or a matter of negotiation based on other rules or principles, including kinship, sharing, stewardship, use, and need (Akaateba, 2019; Brightman, 2010; Brightman, Fausto, & Grotti, V. (Eds.)., 2016; Carpenter, Katyal, & Riley, 2009; Dahl, 2000; Hann, 1998; Goody, 1962; Lowie, 1949; Mauss, 1925; Nagan, 2013; Nagan & Hammer, 2013; Santos-Granero, 2009; Tobin, 2014; Woodburn, 1998). Even in some cases where first mover norms might seem to apply, like “first comer” principles of land ownership in West Africa, those principles do not actually assign ownership to individuals, but rather to lineages within which other principles determine individual rights (Lentz, 2006). For land, a principle of stewardship by current users often takes precedence over any form of permanent, individual ownership, even if others used the land before (Brightman et al., 2016; Carpenter, Katyal, & Riley, 2008; Descola, 1982; Hann, 1998). Against this backdrop, the universality of first-mover norms is far from clear, especially if we mean rules determining who actually owns something, and whether and how those apply across contexts.

Here, we use an experimental method to examine intuitions about first mover norms among adults in an Achuar community in Ecuador, where cultural rules about ownership are likely to diverge significantly from those seen in the European diaspora. We compare these to a sample of American adults using the same materials and show that first mover intuitions, while robustly present in American adults, are not strongly endorsed by Achuar adults: they are weaker, and variable across domains.

It's likely that all humans have the capacity to own things, and to recognize ownership in others. However, the question of whether there is a specific, species-typical human psychology of ownership, and whether that psychology contains particular rules or principles, remains an open one. In principle, it is possible that ownership is a purely cultural phenomenon. But there may also be evolutionary roots to how we conceptualize ownership and the domains to which ownership is extended. How we would tease these apart remains very much an open question.

From an evolutionary perspective, the idea of ownership as an evolved trait gains plausibility because of the presence of ownership-like phenomena—specifically, physical possession and the ability to exclude others—in non-human animals (Brosnan, 2011).

However, there are many ways in which human phenomena of ownership differ from those seen in other animals. One is that while possession and control of resources by force or threat of force are widely seen in other animals, the phenomenon of deference to publicly recognized owners is less phylogenetically widespread in other species (Kanngiesser, Rossano, Frickel, Tomm, & Tomasello, 2020). Another is that human ownership is clearly heavily governed by cultural norms, rules, and worldviews, both implicit and explicit (Brightman et al., 2016; Hann, 1998; Stake, 2004). Clearly, not all norms of ownership are culturally or historically universal, raising the question of what, if any, rules or principles might be universal components of an evolved ownership psychology. Different literatures paint different pictures of what aspects of ownership might be universal or variable across cultures, people, and history.

Much of the psychology literature on ownership has looked for universals, including the emergence of ownership intuitions in childhood as possible evidence for universality. One influential approach to ownership in psychology is a “naïve theory” approach, similar to approaches to naïve or intuitive theories of mind and of physics (Carey & Spelke, 1994). According to this approach, the naïve theory of ownership is part of an evolved core domain of cognition that provides universal psychological building blocks that are in turn shaped by culture and personal experience (Nancekivell et al., 2019). On this view, the human naïve theory of ownership is characterized by a distinct ontology—a set of principles about what ownership is, what can be owned, who can own it, rights and obligations, etc—and principles of causal-explanatory reasoning that are used to predict, for example, how people will respond to claims of ownership, violations of core principles of ownership, and behavior with respect to owned items.

The naïve theory approach to ownership explicitly accepts that ownership norms are in part culturally shaped, but also suggests that there will be universal, or widely shared, intuitions and principles of ownership. These include heuristics for deciding who owns something, based on their prior history with that object or entity. Here we use the term first mover to describe a category of such rules or heuristics. These include principles of first possession and effort, as well as other possible principles such as first pursuit and creation (Friedman & Neary, 2008; Levene, Starmans, & Friedman, 2015; Rochat, 2011; Rochat et al., 2014). For land, such principles also include first comer or first arrival rules (Lentz, 2006; Verkuyten, Sierksma, & Martinovic, 2015; Verkuyten, Sierksma, & Thijs, 2015). Each of these principles is an intuitive rule that assigns ownership of an entity to an individual who did something first, longest, or most effortfully with respect to that entity. For example, the first possessor rule assigns ownership of an object to the first person who possessed it (Friedman & Neary, 2008; Lueck, 1995). Effort rules assign ownership to the person who provided the most labor to obtain, build, or create the item (Friedman, 2010). As studied in psychology, these rules have typically been proposed to apply to individuals, i.e., individual persons, rather than groups.

Table 1 provides a selective summary of prior studies investigating first possessor and effort rules.

Psychological research, especially developmental research on children's ownership intuitions, has provided evidence for each of these rules. In the absence of verbal information (e.g., information that states claims of ownership), children utilize cues such as prior possession, effort in procuring, modification of an object or resource, and the transference of an ownership claim to attribute ownership rights (Friedman et al., 2011). As shown in Table 1, many developmental studies have provided evidence for a first possession principle of ownership in children. Some of these studies show that first possession acts as a heuristic that can sometimes be modulated or overridden by other factors. For example, the assumption that possession implies ownership can be overridden when the means by which the item was gained are questioned (e.g., theft) (Friedman, 2010).

Effort is another factor that can play a role in ownership judgments. Early experimental work by Hook (1993) and Beggan and Brown (1994) found that prior use and investment of labor into an item established ownership rights over that item. Later work has shown that effort can interact with and even override first possession (Friedman, 2010; Verkuyten, Sierksma and Thijs, 2015). Additionally, ownership is ascribed at a higher rate to effort directed purposefully rather than by accident (Li et al., 2013; Palamar et al., 2012).

Relatively few developmental studies have investigated the first possessor rule related to land (see Table 1). Verkuyten, Sierksma, and Martinovic (2015) examined judgments of 9 to 12 year old Dutch children about individual ownership of land. The majority of children accorded ownership rights to the individual who first arrived on a piece of land. However, a follow-up found that first arrivers who work the land are judged to own the land more than those who do not. In a second study, Verkuyten, Sierksma, and Thijs (2015) examined Dutch 9 to 12 year olds' intuitions about group owbership of land, finding that children judged the group that was first to arrive on an island as the owners of the island, independent of how long they had been there. Another study that did not look at first possessor rules per se examined a sample of U.S. and Palestinian children's judgments about how factors such as wealth or poverty, and ingroup affiliation (to the child), should determine ownership of land (Zebian & Rochat, 2012). Children in both groups showed inequity aversion judgments, leaning in favor of a poor versus rich person's claims to a previously unowned piece of land, with weaker evidence for biases towards ingroup members as owners.

The research discussed in this section highlights a prominent gap in the psychological literature: cross-cultural experimental research in settings not situated in the global north is limited. While there is a small cross-cultural literature that examines intuitive ownership rules in non-Western contexts, the vast majority of psychological studies have used standard convenience samples (but see Kanngiesser et al., 2014; Rochat et al., 2014; Da Silva et al., 2014; Kanngiesser, Itakura, et al., 2015). Some work has found evidence for first possessor rules in children across cultures, but sometimes with different developmental trajectories (Kanngiesser et al., 2014; Kanngiesser, Rossano and Tomasello, 2015). Other cross-cultural studies have found some support for the universality of other principles, such as the ownership rights afforded to a creator of an object (Yang et al., 2014).

The picture from psychology, then, is largely one of universality, in which first mover intuitions develop reliably in childhood, with some variability in development. This stands in contrast to the ethnographic literature, which suggests considerable variability in the norms or rules that adults use to assign ownership across cultures, and throughout history.

Literatures in anthropology, history, and economics have documented how rules for ownership have varied across space and time, including rules for who can own things, what things can be owned, how ownership is determined, and the rights and obligations of owners. The ethnographic literature documents a range of ownership principles for different kinds of entities, from land, to food, to human-made artifacts and intangible property including songs, ecological knowledge, and other kinds of cultural property (Akaateba, 2019; Bremner & Lu, 2006; Brightman et al., 2016; Carpenter et al., 2009; Dahl, 2000; Descola, 1982; Earle, 1998; Gluckman, 1965; Graziadei & Smith, 2017; Greene & Drescher, 1994; Gurven, 2004; Hann, 1998; Lentz, 2006; Lueck, 1995; Man & Thambiah, 2020; Lowie, 1949; Mauss, 1925; Nagan, 2013; Nagan & Hammer, 2013; Petersen, 2003; Riley, 2000; Santos-Granero, 2009; Schlager & Ostrom, 1992; Wiessner, 1982; Woodburn, 1998). The ethnographic record reflects a necessity for nuance in the examination of ownership. Sometimes things can be individually owned, and sometimes not. Sometimes the first possessor has a right of ownership, and sometimes not. Importantly, while factors such as first possession, intent to possess, effort, improvement, etc., are often recognized by observers, how these determine who actually gets to own something (if at all), and what rights the person has regarding that thing, are highly variable. Moreover, many commentators have noted that the extreme emphasis on and protection of individual ownership in Western capitalist traditions is much less pronounced in other cultural traditions, suggesting that a rule like first possession might be less widely applicable elsewhere, and in more limited contexts (Buchanan, 1993; Hann, 1998; Hartley, 2019; Harvey, 2007; MacPherson, 1962; Nagan & Hammer, 2013; Riley, 2000; Tobin, 2014).

Because our study focuses on ownership in two domains—hunted foods and land—we note two general observations from the ethnographic literature. First, rules for ownership of food and land are variable across cultures. Second, principles for ownership of food are nearly always different in important ways from principles for ownership of land, even within cultures (including the U.S.). This is not to say that principles such as first possession can't matter in these domains, but rarely is it simply applicable in the way experimental psychology studies might imply. Often it is at best a tie breaker when other principles don't apply. For reasons of space we cannot conduct a full survey of the ethnographic literatures on food and land ownership here, but we offer some brief observations to support the idea that rules for ownership are variable within and between these domains across cultures, and that studies from Western contexts might not offer the best support for the universality of first mover norms.

Rules for ownership of food are likely to differ between industrialized societies where most food is purchased, agricultural and pastoralist societies where food is self-produced, and foraging societies where food is gathered and hunted. Rules for food distribution and ownership are among the most discussed in the classic anthropological literature. In particular, rules for sharing of hunted game in foraging societies have been heavily studied and discussed, forming the basis of many theories and debates about the nature of human sociality and cooperation (Gurven, 2004; Hames, 1990; Wiessner, 1982; Woodburn, 1998). Hunting societies are known for having elaborate rules for food sharing, and in some cases, rules explicitly designed to remove rights of distribution of prey from the person who captured it—a key element of “ownership” that seems not to apply to first possessors in these communities (Bird-David, 1990; Woodburn, 1998). That said, the ethnographic literature does document a “first pursuer” rule of ownership in some cases, which can even include the right to decide how game is distributed (Gluckman, 1965). First mover rules that have been reported in the case of hunting include first to see, first to inflict a wound, first to kill, and first weapon to strike, even if the owner of the weapon was not the first to strike. Again, however, attribution of a kill to an individual might be separable from “ownership” in some cases, especially where ownership implies right to distribute. For example, the distribution of hunted game meat among the Ache is often done by an older man in the hunting party (Gurven, Hill, & Jakugi, 2004). Among Aboriginal groups of the Western Desert of Australia, food is split by a set number of pieces among individuals, with the hunter responsible for the kill having no say (Gould, 2019). What these examples show is that even in cases such as killing a prey animal, where a concept like “first possession” makes sense, cultural rules do not always bestow rights of ownership, such as rights to distribute or even consume the animal, on the first possessor.

Principles of land ownership are notoriously far more complicated across cultures and throughout history. While some psychological studies have shown that children can exhibit a first possessor intuition for land ownership (Verkuyten, Sierksma, & Martinovic, 2015; Verkuyten, Sierksma, & Thijs, 2015), this does not necessarily reflect the realities of how land ownership is actually assigned in much or most of the world across history. While some historians and social theorists, such as Marx and Proudhon, have suggested that private ownership of land is a recent phenomenon, this depends to a degree on what is meant by ownership (and even, in some cases, individuals). What is extremely well-documented in the ethnographic and historical literatures is collective or group ownership of, or rights to use, land (as well as, e.g., hunting and fishing grounds) (Bremner & Lu, 2006; Dahl, 2000; Descola, 1982; Lentz, 2006; Man & Thambiah, 2020; Nagan & Hammer, 2013; Schlager & Ostrom, 1992). Importantly, in many Indigenous communities this can include places such as sacred sites or other areas of communal use, such as hunting grounds, that are not owned and could not, even conceptually, be owned by anyone. But neither does this make them fair game for taking, or “unowned.” They are neither considered wilderness, nor unused or abandoned. They “belong” to the community, and community members have various rights and duties with respect to them, but to think of them in terms of ownership (or lack thereof) makes little sense. Importantly, this can apply to other kinds of property as well, including intangible goods (“cultural property”) and other culturally significant items (Carpenter et al., 2009).

Within many Indigenous communities, then, it is common if not typical for there to be no principle of indefinite, individual ownership of land. Land could be regarded as “collectively” owned, but even then this is often not exactly the way communities traditionally think of land, and categories like individual versus collective ownership make little sense locally (Hammer, Jintiach, & Tsakimp, 2013; Leach, 2016; Nagan & Hammer, 2013). Sometimes, collective ownership is a legal category sought by Indigenous communities to prevent settler encroachment and land appropriation (Blackman, Corral, Lima, & Asner, 2017; Bremner & Lu, 2006; Buntaine, Hamilton, & Millones, 2015; Nagan, 2013; Nagan & Hammer, 2013; Rubenstein, 2002). Within many communities that have ownership or sovereignty over a territory, individual “rights” to land are often assigned or recognized within that territory, such as the right to build a house a clear land for a garden, or exclusive rights for an individual or a group to hunt in an area (Akaateba, 2019; Bremner & Lu, 2006; Descola, 1982). Often, in places such as Amazonia, such rights are temporary and must be constantly renewed through maintenance and use or lost, reverting to the community (Brightman, 2010; Carneiro da Cunha & Viveiros de Castro, 1985; Viegas, 2016). While “effort” is part of what is needed to retain these rights, it would perhaps be better to call the principle of temporary ownership in these cases a principle of stewardship, or productive use (Carpenter et al., 2009; Descola, 1982; Petersen, 2003). Hunting and fishing grounds can also be assigned and held based on similar factors (e.g., use and stewardship), though they are also in some communities considered to be hereditary by kindship, clan, or descent group.

Importantly, in all of these cases some forms of ownership exist. Notably, however, these rights are not always or even typically what would be called individual ownership rights under U.S. or European law, since individuals or families are merely stewards of property whose disposition is still within the control of the group. In such contexts, which arguably represent either the majority or at least a large portion of human land ownership systems throughout history, principles such as “first possession” can exist, though they are likely to have more circumscribed meanings than in, for example, the U.S. Homestead Act of 1862, in which first possessors literally come to own the land in perpetuity, provided they improve and maintain it (Lueck, 1995). In many other places, such individualistic and exclusionary rights would be considered both absurd and immoral, as exclusionary ownership disregards the potential needs of other members of the community. In some parts of West Africa, “first comer” principles assign communal land to lineages or communities that are regarded as having arrived their first—a kind of group first possessor rule that also applies in many Indigenous communities, including the Shuar and Achuar (Bremner & Lu, 2006; Descola, 1982; Lentz, 2006). In some such systems, first comers can stake claims to currently unused land, but often this is not a strong or even valid consideration for how land is allocated to individuals and families within a community, which can more often be based on need, availability, fairness, and other principles such as kinship.

While brief, this review of the ethnographic literature on ownership in the domains of food and land ownership highlights several points that motivate the present study. While psychological studies of ownership judgments have provided valuable evidence for first mover intuitions as a potential psychological principle for allocating ownership, these studies have focused largely on children's intuitions, and largely children from communities in the U.S. and Europe that are steeped in Western, capitalist traditions. Moreover, because children and adults in these communities have grown up in cultural and political systems that emphasize the importance of individual property ownership and the role of individual agency in obtaining it, they might be particularly prone to favor first mover rules for assigning ownership. Because the anthropological literature, and Indigenous communities themselves, emphasize the relative importance of other principles for assigning ownership in these communities, these might be particularly important places in which to investigate the hypothesis that first mover norms are intuitive universals (Carpenter et al., 2009). Indeed, Achuar and other Indigenous communities are especially relevant for studying putative universals that might instead represent cultural values spread via colonialism, because many of these communities actively resist and refuse values and customs imposed from the outside (Simpson, 2014).

For these reasons, we decided to examine ownership intuitions in an Indigenous Achuar community that has different ownership traditions than those of other, typically Western communities in which prior psychological studies have been conducted. We used the standard, vignette-based method used in experimental psychology studies to elicit ownership intuitions in adult members of an Achuar community in Ecuador, and to compare these with intuitions of an online sample of U.S. adults on the same materials.

Achuar communities provide an interesting and useful case study to test hypotheses about a universal ownership psychology due to their complex cultural history and shifting individual psychologies related to changing economic and political conditions within the Pastaza region of Ecuador. The Achuar are an Indigenous Amazonian society living in Southeastern Ecuador and are a part of the larger Aents Chicham cultural-linguistic group that includes the Shuar, Shiwiar, Awajún, and Wampís (Deshoullière & Utitiaj Paati, 2019). Here we describe shared social customs of Achuar and Shuar communities, as we have understood them, together.

For the study of ownership, Achuar communities are notable because of a mix of cultural norms that combine respect for the autonomy of individuals (particularly male heads of households) with a strong communal or collectivist ethos (Brown, 1985; Descola, 1982, Descola, 1986, Descola, 1996; Juank, 1994; Mader, 1999; Rubenstein, 2002). This makes Achuar communities difficult to situate in the classic collectivist/individualist continuum (Barrett, 2018). Political organization in the Achuar, and in Chicham-speaking communities more generally, is egalitarian in that it frowns upon strongly hierarchical power relations. Community affairs and decision-making are highly democratic, organized around communal consensus about the use of community resources and the resolution of disputes. Villages have elected presidents, but these are recently created political positions, and presidents do not generally hold special social power outside of their bureaucratic responsibilities.

In most Achuar communities, including the one studied here, there is no official (state-based) individual title to land. In this community, as for many Indigenous communities in Ecuador, the land is legally owned collectively, by an association of Achuar communities (Nagan & Hammer, 2013; Rubenstein, 2002). Individual ownership of land is maintained by community recognition, within a larger territory that is managed by the Achuar nation and organized around centros, or villages (Bremner & Lu, 2006; Descola, 1982; López, Beard, & Sierra, 2013; Rubenstein, 2002). Since the law does not grant individual rights to land nor determine boundaries between individual and communal land or even between entire villages, these are matters of collective social and political recognition that must constantly be maintained and sometimes renegotiated, consistent with norms of land stewardship across many Indigenous Amazonian communities (Brightman, 2010; Viegas, 2016).

While these features point towards an egalitarian, collectivist ethos, Achuar communities are also noted for their strong respect for individual rights and autonomy, especially regarding decision-making within households (Descola, 1996). Household decision-making is gendered and typically biased towards men, but women also exert substantial economic, political, and social power. Ownership of many things is recognized in Achuar communities, including individual goods, food, and pets.

For land, such as houses, gardens, and hunting territories, there is no traditional principle of permanent ownership akin to legal title. Instead, ownership is a form of stewardship during a period of active use. Individuals are granted land by community recognition, which they are then able to use so long as they curate and maintain it. Household plots are recognized as owned as long as the family lives there, and are traditionally seen as reverting to the community if the family moves, via migration or if the head of household dies (Descola, 1982). Families are recognized as having rights to land that they are using for farming and gardening, provided that they continue to invest in its maintenance and productivity. Hunting territories, too, are typically regarded as being the property of households or families, who have the right to exclude others, but this is also subject to a principle of use and maintenance, and no family is seen as having permanent claims to land outside the recognition of the local community (Descola, 1982, Descola, 1986). When land becomes abandoned or disused, rights to that land are generally regarded as reverting back to the community (Bremner & Lu, 2006). Again, this represents a principle of temporality of land stewardship that is seen in many Amazonian communities, associated with an idea of constant, eternal cycles: the abandonment, renewal, and “re-opening of new places,” as Viegas (2016), p. 241) describes for Tupinamba communities in Brazil (Brightman et al., 2016; Santos-Granero, 2009).

For food, there are strong sharing norms (Descola, 1986, Descola, 1996). The Achuar practice is a version of customary food sharing where meat from hunting is expected to be shared widely, often given spontaneously in the form of gifts or an invitation to a hosted party. Hospitality rules require families to welcome visitors and to share food and drink generously. Obligations to assist others, including kin, friends, and even strangers, can be very strong, making requests for assistance hard to deny. Thus, while ownership is strongly recognized and valorized, selfishness is not. Ownership bestows rights, but greedily holding onto resources when others are in need is heavily frowned upon. Finally, there is ownership of cultural knowledge such as songs, recipes, and techniques for making artifacts, such as pottery, baskets, weapons, furniture, and other personal items. Some knowledge can be seen as individually owned but is simultaneously recognized as traditional knowledge that is passed from individual to individual (i.e., among families), and thus should not be individually hoarded. At the same time, such knowledge is tacitly regarded as a form of group cultural property, not merely free for appropriation or use by anyone without relevant community standing (Carpenter et al., 2009; Nagan, Mordujovich, Otvos, & Taylor, 2010).

Together, this combination of cultural values and practices makes Achuar communities an interesting place to study ownership norms and to test hypotheses about universal principles of ownership such as first mover principles. On the one hand, respect for individual rights and the valuation of personal effort and industriousness are very strong. Since many if not most possessions, like homes, gardens, and money, are the products of individual labor, people are justly proud of what they own. At the same time, selfishness and greediness are among the most stigmatized traits in Achuar communities, suggesting that people should not hold on to their possessions too dearly. Resources are given away generously and spontaneously, often with no expectation of thanks or compensation of any kind.

What does this mean for ownership psychology in Achuar communities? Some features mentioned above, such as strong individualism and respect for personal labor and effort, might lead us to expect norms such as norms of first possession, pursuit, or effort in determining ownership. On the other hand, this is a society where resources, even hard-earned ones, trade hands routinely and with little fuss. What does this mean when two people have competing claims to the same object, as in the vignette-style scenarios that are typically used to test ownership rules in psychology? Perhaps it means that rules such as first possessor or first pursuit will not be seen as definitive tie-breakers or adjudicators of ownership, as they are seen in some other societies. Given that resources such as land and meat are thought of quite differently, perhaps different rules could apply to different domains of ownership. Because land is held communally, who finds a piece of land first might not be regarded as bestowing ownership. Instead, principles of stewardship based on current use or maintenance might override a first possessor rule. For hunted foods, while we expect recognition that a particular hunter was first to capture or possess the prey, it is not clear whether this will lead to judgments of ownership, or how competing principles of effort and first possession might trade off.

Here, we investigated these questions using experimental vignette methods like the ones used in many psychological studies of ownership, in which participants were presented with scenarios where two individuals had potential claims to ownership. We examined ownership intuitions in two distinct but culturally relevant domains: land, and hunting.

In our scenarios, there was always a first possessor. Thus, across all scenarios we were able to construct statistical models that estimated the probability of judging in favor of the first possessor. However, we also varied other factors that might weigh against first possessor judgments. We varied the amount of effort used by the second party to obtain the item. Crucially, in the hunting scenarios, the first possessor was always the one to exert less effort but ended up possessing the animal. In the land scenarios, the second party ended up building a house on the land, contrasting the use / stewardship principle with first possession. Additionally, we varied whether the land in question was considered communal land or not.

For comparability to prior studies in psychology reviewed above, we used an experimental vignette method, tailored so that the scenarios were culturally appropriate to the Achuar, but could also be understood by a sample of U.S. participants, who we recruited via the Amazon mTurk platform.