Individual property is a rarity in most species of nonhuman primates, most likely because their lifestyles are not conducive to the maintenance of property. Nonetheless, just because these species do not frequently maintain property does not mean that they lack the propensity to do so. Recent research from the CEBUS lab has shed light on primates' concepts of property. First, we find that chimpanzees and capuchins are quite good at barter between themselves and a human experimenter, and appropriately respond based on the value of the objects. Moreover, chimpanzees will barter with conspecifics, yet ceased doing so as soon as experimenter control was removed. Property concepts beyond possession may be challenging for chimpanzees due to the risks involved when social and institutional controls for maintaining property (e.g. gossip or legal mechanisms) are lacking.
Second, we have found evidence of an endowment effect in several apes, similar to that seen in humans. These individuals prefer to maintain property that they have in their possession over trading it for something that they prefer in a free-choice context, showing that they and we share biases in common with respect to property in common. Moreover, these apes can be used as a model system to study these property biases. For instance, new research in our lab shows that chimpanzees show the endowment effect for food objects, but not for toys, and for tools that can be used to get food, but only when that food is both visible and immediately accessible. Thus, for identical items, the endowment effect is only triggered when that item is immediately useful in an evolutionarily relevant context. I have recently received a grant with psychologist Rebecca Williamson to use the non-verbal methods we developed for primates to test young children. We will explore at what age they begin to show the effect, and how properties such as physical possession (vs. property without actual possession) and symbols of property influence the perception of children that something is “theirs.” By comparing these data, we gain perspective on how human property concepts have evolved.