Monkeys evolve a new way to communicate with humans

Leslee Lazar

Monkey making an intentional call
Monkey making an intentional call   (Photo: Leslee Lazar)

If you have ever lived in a place with monkey menace, you would know that monkeys are highly intelligent and have impressive ability to use tools. They can open latches, screw cap bottles and door handles and are very efficient in getting food even in urban settings. Monkeys can also communicate with other monkeys using gestures and vocal calls, for example they have separate calls for when they are in danger and for food availability. However, could their communication be considered as a language system or is it just reflexive gesturing or calls?

One of the main features of language is intentionality, which means that the animal can understand the mental state of the animal it is communicating to. This intentionality can manifest in different ways. Two communicating humans can understand each other’s intentions, mental states and goals and intentions. This ability is called ‘theory of mind’. David Premack in his classic 1978 paper- “Does the chimpanzee have a theory of mind?”- showed that chimpanzees can also understand the intention of a human actor. However, intentionality can also occur without theory of mind, like in captive monkeys, where studies have shown intentional communication between monkeys and human caregivers.

When it comes to wild monkeys, the issue is contentious. Anindya Sinha and his group from National Institute of Advanced Studies, Bangalore, who study communication behaviour of troupes of wild bonnet macaques (Macaca radiata) in the Bandipur area in Karnataka, have shown that wild bonnet macaques show intentionality while signalling among conspecific members within a troupe. In a new study published in Scientific Reports they have showed that wild macaque monkeys make intentional novel communication with humans using vocal calls and gestures to ask for food. When the human had food, the monkeys made a hand extension gesture with an open palm towards the human. This is new behaviour, which is different from other food reaching or handling behaviour seen in the wild. These monkeys also orient their head towards the human, monitoring their reaction and adjusting their posture to get the attention of the human. The monkeys persist until the food reward is obtained and made a specific coo-call during this interaction.

The authors say that this is the first documented evidence of such behaviour in monkeys in the wild. To prove intentionality of this gesture, the authors say that it passes the criteria for intentionality established by previous research in other monkey species. Adwait Deshpande who is the first author in the paper says “We showed that monkeys use hand extension gesture depending on the attentional state of human receiver. They perform this gesture only when humans are directly looking at them. This is an evidence for underlying intentionality.”

This shows that the monkeys have the mental capability to communicate flexibly with humans. They were able to figure out if the human is paying attention. If the human is not paying attention, they change their posture to make their presence felt. Finally, they persist in the communicative gesture until food is delivered. They gestured only when they encountered a human with food and stopped when they got the food.

This study shows for the first time, wild untrained monkeys communicating intentionally with unfamiliar humans using a novel communicative gesture. Intentionality is an important concept in understanding consciousness. Daniel Dennett, the philosopher coined the phrase ‘intentional stance’ to indicate the highest level of analysis by an organism, which is to understand other’s mental state and predict their behaviour. Intentionality is also the cornerstone of evolution of language in humans. This study shows that the building blocks needed for the evolution of language is present in the monkeys.

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