Why do we use tools? Investigating the drivers of tool use in non-humans and humans

Pr. Thibaud Gruber - FNS Eccellenza

Humans stand out among all other animals, even among their own family, primates. Our uniqueness has been attributed to several factors, most often to our amazing faculties as social learners and teachers, some of the building blocks of our cultures. The first described human cultures are made of tools, and tools also constitute the bulk of most animal material cultures described so far. Yet, it is still unknown what proximate factors make a species use tools. On the one hand, over the last two decades, several ecological hypotheses have been proposed to explain the occurrence of tool use in various animal species, particularly great apes and tool-using birds. For example, the necessity hypothesis states that animals will only use tools when their favorite food is low in the environment. To the contrary, the opportunity hypothesis states that animals’ propensity to use tools is correlated to the probability of encountering possible tools and substrates in the environment. However, the methodology to assess necessity and opportunity may have to be rethought: a starving animal encountering an ecological opportunity for tool use is different from a satiated one and it is yet unclear how much this impacts its behavior. On the other hand, the environment faced by an individual is not limited to ecological factors. Most cultural animals, particularly humans, live in a complex social world where one’s own experience is mediated by others’ experience. Getting information from them is crucial to decide the next move. While much work has been devoted to the social learning of tool use in various species, there is yet a lack of research on the emotional aspects of social transmission, both in humans and other animal species.

This project will study both the social and ecological aspects of tool use in an attempt to characterize the drivers of tool use in two species that have a large material culture: humans (Homo sapiens) and chimpanzees (Pan troglodytes). In particular, it will focus on two drivers that have been overlooked so far: the emotional characteristic inherent to social transmission (external driver), and the energetic aspects that mediate an individual’s motivation to engage with a given environmental opportunity (internal driver). With respect to emotions, we will run experiments with children whom we will expose to a particular emotional environment prior to engaging in tool use tasks. For example, a group of children will first engage in memory or manipulation tasks with a friendly experimenter at various intervals within two weeks before engaging with tool use learning and innovation tasks. In contrast, other children will not be exposed to any experience with the experimenter before engaging with the tool use tasks. We will run these experiments in several cultural groups and in different schooling systems, including Western formal or Montessori schools, and Ugandan rural areas. We will also conduct a similar ontogenetic study in chimpanzees. This first research objective will thus particularly focus on how establishing an emotional bond with a potential model, or simply a caretaker, can foster innovation, imitation or overimitation (the imitation of meaningless actions) in a youngster. The second research objective will use field and campus experiments to investigate how energetic variations influence the use of tools and problem-solving abilities. This project will rely on field experiments in chimpanzees, using the well-tested honey-trap experiment in a newly habituated community of wild chimpanzees. The honey-trap experiment consists in trying to access honey in a hole dug in a log through the use of tools. Chimpanzees’ energy balance will be assessed through Urinary C-peptide (UCP) testing. We will also run similar experiments and collect physiological data with human adults on campus to assess the same parameters on comparable problems. This work will be conducted in the wild for chimpanzees and in the laboratory for humans to cover the most ecologically valid settings. In addition, when possible, tasks will be designed to be transferable to non-primates for short-term complementary studies with comparative purpose.

This project at the Faculty of Psychology and Education Sciences at the University of Geneva therefore aims to integrate in a general model of tool use two drivers that are critical in explaining our motivation to use tools. That humans surpass other species is not informative if we do not understand how processes inherited from our primate lineage evolved. Integrating developmental, comparative, and ecological approaches will be crucial to determine how ecological and social factors interacted to lead to tool use. Finally, the results of this research will be of interest beyond academia by studying the impact of emotion and energetics on learning in two populations in the process of building knowledge: children and students.

Team