CEU Researchers Investigate Human-Like Communication by Great Apes

Not only humans but also other primate species use their fingers to point in order to communicate. That’s the result of a new study by a team of researchers from CEU and the Max Plank Institute. The team was examining whether great apes use human-like gestures to communicate. As a result of the close cooperation between the researchers, their findings were published by Nature Scientific Reports. 

The great apes were tested in the Zoo of Lepizig between January-April 2017 by Tibor Tauzin of CEU’s Department of Cognitive Science and Josep Call. The co-author of the article, Manuel Bohn (Leipzig University), was supported by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant.

Humans’ unique ability to use language clearly distinguishes us from any other species. It is less obvious, however, that the versatile ability to invent, produce and interpret non-linguistic gestures is also human-specific. More and more evidence support theories that human communication originates in non-linguistic gesture and that we share this with other species of primates.  

A team of scientists at Central European University and Max Planck Institute investigated this question, aiming to understand whether non-human primate species can point at objects in order to receive them – similar to how human infants and toddlers do this. 

Previous studies have shown that chimpanzees, gorillas and orangutans (among other species) evidence a pointing-like behavior when a desired piece of food is not immediately accessible - because it is behind a mesh, for example. Nevertheless, it was an open question whether this behavior is indeed a communicative pointing or a reaching action prevented by the mesh panel. 

“Although such gestures are only produced when a human is around, which is against the ‘failed reaching’ interpretation, the pointing behavior of non-human primates seemed less flexible than what infants are capable of, based on these original studies” said Tibor Tauzin, a researcher at CEU.

According to Tauzin, “even young human infants consider the perspective of the communicative partner and the arrangement of the potentially relevant objects in order to produce clear pointing at the desired object. Therefore, to claim that non-human primates can use pointing just like us, it was inevitable to test the ability of apes to modify and adjust their pointing to the context.”

To test the hypothesis, the researchers placed two pieces of food in a way that one was behind the other. While one of the food items was a favorite of apes (a grape) the other was less desirable (a slice of carrot). In the experiment, the grape was positioned behind the carrot with the ape closest to the carrot while its human communicative partner was closest to the grape. If the ape wanted to request aid from the human, the latter’s perspective of him needed to be taken into account. Consequently, apes had to point in such a way as for the meaning to be unambiguous – for example, by indicating the grape from the sides or from above. 

While the task was new for the subjects, they were all able to modify their pointing when the grape was further away from them, indicating it from the sides. However, they almost never did so when the grape was directly in front them.

This suggests that non-human great apes are capable of produce human-like pointing actions, which supports the hypothesis that our common ancestors might have had the same ability, facilitating the evolution of far more complex and versatile communicative systems – including human language itself.

The study was supported by a European Research Council's (ERC) SOMICS Synergy Grant awarded to Josep Call (University of St. Andrews, School of Psychology and Neuroscience), György Gergely (Central European University, Department of Cognitive Science), Günther Knoblich (Central European University, Department of Cognitive Science) and Dan Sperber (Central European University, Department of Cognitive Science). The principal investigators of the study were Josep Call and György Gergely.

Cover photo by Tibor Tauzin