A study conducted in the African forests has shown that the Bonobo, primates of our “cousins”, have the ability to combine their calls in a similar way to what happens in human language.
The Bonobo, who with chimpanzees are our closest living relatives, have a lot in common with us. Now one more thing has been discovered: they know how to create complex combinations of calls, in a similar way to how we humans combine words. This is what emerged in a study led by Mélissa Berthet of the University of Zurich (Switzerland), to whom we dedicate a study on Evidence Network on newsstands. This ability is called compositionality: the ability to combine elements in sentences whose meaning derives from that of the individual parts. Mélissa Berthet recorded the Bonobo calls, which you can listen to above, and analyzed them. In this interview, he tells us how she and colleagues conducted the study and what the results were.
By recording the Bonobo calls, he created a true “dictionary” vocalizations. As ha determined the possibilthe meanings?
To investigate the meaning of the Bonobo calls, I conducted a large research in the Bonobo Reserve Kokolopori, in the Democratic Republic of the Congo, for 8 months. I followed the Bonobo of three communities, accustomed to the human presence, for 8-12 hours a day, recording their vocalizations and systematically noting the context in which each call was produced.
For each vocalization, I monitored over 300 contextual parameters, such as the presence of food, if the individual was feeding, cleaning, resting, if he was approached by others, if new individuals were joining the group, if the group had started to move and so on. Correcting these contexts with specific vocalizations, I have been able to deduce the probable meaning of the calls. Over time, this has allowed us to create a sort of “dictionary” of the vocalizations of the Bonobo, a complete mapping of the references and the meanings and associated contexts.
Cor I mention some examples of the meaning of the vocalizations used by the Bonobo?
Yes, there is one that I really like. The Bonobo have the “Yelp” and “Piep” calls, which have a similar meaning: they seem to be used to ask others to do something. However, they are different as Yelp is more an imperative, “Let’s do it!”, While the piece seems more subdued, more similar to a “if you want, we could do …”.
What communicate the calls?
What emerges from our discoveries is that most of the Bonobo calls are used to coordinate the group’s behavior.
Their meaning is often linked to the maintenance of the group unit of the group or to insure that individuals are engaged in the same activity at the same time. This is logical because the Bonobo live in what we call a fiscal-fusion company, in which the members of the group divide into smaller subgroups in the morning and gather later, just like humans who separate for work and gather in the evening. In such a dynamic social system, the calls help individuals remain synchronized and maintain social cohesion. For example, some calls can be associated at the beginning of a trip or the request to join distant groups.
Your research aimed to investigate the ability of the Bonobo to “combine” references, compositionality. THEn which species is this ability present?
Compositionality – the ability to combine significant elements in wider structures, whose overall meaning derives from the meaning of the individual parts – is a fundamental characteristic of human language. Until recently, it was thought to be largely exclusive to human beings. However, now we know that Japanese cincialegrege and another bird such as the southern Juventus Garrulo, as well as records such as chimpanzees can produce at least one combination of calls. The fact that the chimpanzees had this ability suggested that even our last common ancestor with chimpanzees and Bonobo owned it. To verify this hypothesis and make sure that it had not evolved independently of the two lineages, we had to make sure that compositionality was also present in the Bonobo.
And what do you have discovery?
In the Bonobo, we discovered not one, but four combinations. To determine it, we first estimated the meaning of the individual calls and then the combinations, determining the context in which they are issued. In order for a combination to be considered compositional, it had to satisfy three criteria: each element had to have its own distinct meaning; The combination had to have a different meaning from that of each individual part; The meaning of the combination was to be obtained in its parts.
We also examined the type of compositionality. Which can simply add two meanings (as in the expression “blonde dancer”, which indicates a blonde person who is also a dancer) or be more complex, with one element that changes the other (as “bad dancer”, which does not indicate a bad person who is also a dancer, but a dancer that dance badly: bad dancer modification).
We examined if the meaning of the combination was different from the simple addition of the meaning of its parts: three of the four combinations belonged to this more complex type of compositionality, which was thought to be exclusive of human beings.
Cò do Examples of this type of combinations?
For example, a bonobo emits a light “peep”, which means “I would like”, before a whistle, which means “let’s stay together”. This combination is used in situations of social conflict. It seems to mean something like “relax”, perhaps a way to say “I would like us to remain together”. There is another case: a call that means “pay me attention” and one who reports excitement are used together when a Bonobo is attacked and asks for help from others. Maybe it means something like “looking at me because I’m in danger”.
