All studies were based on novel anticipatory looking procedures. Participants viewed movie stories while their gaze was non-invasively tracked and mapped onto the videos. In the movie stories, an actor either demonstrated a preference for one of two objects (desire study) or the actor witnessed an object being hidden in one of two locations (and for one reason or another should come to have a belief about the object's location that differed from what the participant knew to be true; belief studies). In the various stories, the actor then approached the two objects or hiding places, and the researchers measured where participants looked during this approach -- which object or hiding place did participants think the actor was heading toward?
To prepare to address all three objectives, the researchers first performed a review of all research on animal theory of mind, which was published in 2019 in WIREs Cognitive Science.
To address the first objective, investigating children's and apes' understanding of others' desires, the researchers developed a novel desire-understanding eye-tracking task of this sort and tested a sample of children (aged 1.5 to 3 years) and chimpanzees. Consistent with a recently published study, we did not find evidence that children of this age anticipate an actor's search by inferring that the actor has a desire that differs from the child's own. The first chimpanzee participants unfortunately have not shown reliable attention to these videos.
To address the second objective, exploring children's and apes' understanding of others' ignorance, the researchers are drafting a theoretical paper that leverages existing data to argue for an understanding of ignorance in these populations.
To address the third objective, exploring children's and ape's understanding of others' beliefs, the researchers have completed three studies with great apes (one already published in 2019 in PNAS), one study in children (aged 1.5 to 3 years), and are currently collecting complementary samples with human adults. These studies reinforce the view that human adults and great apes share mechanisms for attributing false beliefs to others. Results from children on this task (which was more challenging in some ways that previous tasks) are less clear.
Most likely, when fully published, this body of work will constitute 4 empirical articles and 2 review/theoretical papers. The work has been disseminated over the last two years through three conferences, more than a dozen invited talks at university departments in Europe and North America, several outreach events, and through repeated engagement with the media.
