The elusive perspective of a food thief Eurasian jays fail to take into account the point of view and desire of other jays when hiding food they can eat later

H ow often do you think about what somebody else might know and want? The process of attributing mental states to others is called ‘theory of mind’, and is crucial for humans to successfully navigate social interactions (FeldmanHall and Shenhav, 2019). This ability not only allows us to predict one specific mental state (such as hunger), but also to integrate several so we can form a more complete picture of a person’s perspectives, desires, and knowledge. For example, it allows us to anticipate which snack someone might choose based on their cravings and what foods they can see in front of them. For decades, researchers have been trying to find out whether non-human animals possess social cognitive skills resembling theory of mind (Premack and Woodruff, 1978; for a recent review: Krupenye and Call, 2019). While many studies have focused on whether animals attribute a specific mental state to members of the same species, very little is known about their ability to integrate multiple mental states. Now, in eLife, Nicola Clayton and colleagues from institutions in the United Kingdom, the United States, Croatia and Italy – with Piero Amodio as first author – report experiments investigating whether Eurasian jays are able to comprehend more than one mental state at a time (Amodio et al., 2021b). Eurasian jays belong to the corvid family, which also contains ravens, crows, and magpies. Corvids have relatively big brains and remarkable intelligence, which may have evolved independently despite matching the cognitive levels of primates (Osvath et al., 2014). Like many other corvids, Eurasian jays conceal and cover food items to retrieve them later. However, this caching behaviour is sometimes observed by other jays who might decide to swoop in and steal the hidden food. The resulting dynamics between caching and pilfering resemble an arms race that appears to require complex social skills. Indeed, previous research suggests that jays can interpret other jays’ visual perspectives and desires. For example, jays preferred to cache out of view when observed by another bird (visual perspective; Legg and Clayton, 2014), and males fed their mating partners mostly food types they had not eaten recently (desire; Ostojić et al., 2017). Amodio et al. designed two experiments to test whether a jay deciding what food to cache where can integrate the visual perspective and desire of an onlooking jay who might steal the food. In both experiments, a ‘cacher’ and an ‘observer’ were placed in adjacent aviaries. The observer was fed either macadamia nuts or peanuts in view of the cacher. This causes the observer to lose interest in the type of nut it has Copyright Zeiträg and Jacobs. This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited. Related research article Amodio P, Farrar BG, Krupenye C, Ostojić L, Clayton NS. 2021. Little evidence that Eurasian jays protect their caches by responding to cues about a conspecific’s desire and visual perspective. eLife 10:e69647. doi: 10.7554/ eLife.69647