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Origins of theory of mind: action prediction by great apes and human infants

Periodic Reporting for period 1 - MENTALIZINGORIGINS (Origins of theory of mind: action prediction by great apes and human infants)

Reporting period: 2018-01-01 to 2019-12-31

Theory of mind (ToM) is the ability to take others' perspectives, to think attempt to infer others' goals and beliefs. Our inferences about what others are thinking allow us to deceive and to empathize, to cooperate and to teach. For four decades, researchers have been attempting to elucidate the evolutionary and ontogenetic origins of this critical cognitive ability. In conflict with a long-held consensus, some have begun to argue that human infants (and to some extent great apes) share with human adults even the most cognitively sophisticated representational ToM abilities. To help resolve the intense resulting debate, this project set out to complete a series of targeted experiments to test for several understudied but key ToM skills in great apes and human infants. The skills in question—attribution of (a) desires, (b) ignorance, and (c) false beliefs—form the basis of an animal’s ability to distinguish others’ minds from its own and build sequentially in terms of the apparent complexity of the underlying cognitive mechanisms. Leveraging innovative new anticipatory looking eye-tracking methods and a variety of novel study designs, the researchers performed a series of noninvasive experiments with zoo-housed great apes (chimpanzees, bonobos, orangutans), human adults and children (ages 1-3.5 years). These studies provide evidence that great apes, human adults, and to some extent human children share relatively rich mechanisms for taking others' perspectives. These studies help clarify the developmental and evolutionary origins of the defining features of the human social mind. They also provide tools for measuring social cognition nonverbally that could prove useful for early detection of conditions that are characterized by deficits in social cognition.
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.
The project has furthered our collective understanding of the social cognitive abilities of nonhuman great apes and young human children, the evolutionary and developmental origins of these capacities, and the mechanisms that underlie them in each population as well as in human adults. All species of great apes are endangered in the wild. By illuminating their human-like cognitive skills, and widely disseminating that information alongside information about their conservation plight, the work serves to elevate concern for, and investment in, the conservation of these remarkable creatures. This work also contributes to captive animal welfare through cognitive enrichment and through better understanding of each species' psychology and behavior.

The novel methods developed for the project provide new tools not only for further basic scientific inquiry but potentially also for early detection of social cognitive deficits in young children (e.g. with autism spectrum conditions) or with nonverbal or minimally verbal populations.
Human infant participating in an eye-tracking experiment