When considering language abilities in non-human animals, it pays to keep in mind that spoken words are not the only path to sophisticated communication. For example, while great apes like chimpanzees and orangutans may be limited in their ability to adapt their vocalizations to human speech, they are able to control their hand movements very well, and can engage in extremely expressive and effective gesturing behavior.

In a thought-provoking study first published online last year and now appearing in the August 23, 2011 issue of Biology Letters¹, two Canadian researchers, Anne Russon of Glendon College and Kristin Andrews of York University, reported on their extensive review of data regarding instances in which orangutans in Borneo have used “pantomime” to communicate with their target audiences.

What part of "give me more food" don't you understand? (photo credit: Tom Low)

Russon and Andrews mined 20 years’ data that had been collected during systematic observational studies on the behavior of ex-captive orangutans as they underwent rehabilitation and were living free or semi-free lives in the forest. After reviewing original field notes and videos covering over 7,000 hours of observation, they identified 18 salient pantomime cases (14 addressed to humans and four to other orangutans) in which orangutans physically acted out messages in order to communicate specific goals.

In most of the cases, the orangutans used pantomime to provide additional or better information after an initial attempt at communication had failed – for example, by being more specific about an action, item or tool requested; by offering better tools for a requested task after a previous tool had been ignored; by pretending to be unable to perform a task after a request for help had been ignored; or by clarifying friendly intent after non-aggressive approaches had been refused.

A few specific examples will help to illustrate how the orangutans used pantomime to achieve specific communication goals:

• An adolescent female named Siti, who had partially opened and eaten a coconut, handed it to a technician who in turn handed it back to her, gesturing to her that she should finish the job. She proceeded to briefly, weakly and ineffectively poke at the coconut (very much in contrast to her prior behavior), before handing it back to the technician. When he again refused to help her, she used a palm petiole (stalk) to chop at the coconut repeatedly, as one would with a machete. Russon and Andrews described their interpretation of the incident in the data supplement to their paper:

After [the technician’s] first refusal she faked inability to do the job herself; after the second refusal she elaborated her request by acting out what she wanted done, specifying what tool and target to use and how to use the tool.  She acted out the actions she wanted of her partner, which included a skill that was not in her own repertoire (machete use).  Given the complex conjunction of conditions and the specificity of her request, Siti’s pantomime must have been invented on the spot even if she was familiar with all constituent elements.

Fortunately, you can see this incident for yourself, as there’s a video of Siti and the coconut – enjoy!

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• After a three year old female named Kikan had hurt her foot on a sharp stone, a research assistant removed the stone and dripped latex from the stem of a fig leaf on the wound to help make it heal faster. After that, Kikan (who had previously not been particularly friendly with the assistant, hitting or trying to bite her when she passed by) approached the assistant in a friendly manner on a number of occasions, holding up her wounded foot for the assistant to see. On one specific occasion, Kikan picked up a leaf, pulled the assistant’s hand until she paid attention, and then acted out the leaf treatment the assistant had given to the foot. (This is not only interesting for its communication content, but it could be an indication of episodic-like memory (mental time travel), a topic that Felicity Muth recently discussed in some detail in two Scientific American blog posts, here and here).

• An adult female named Unyuk played with forest assistant who pretended to give her a haircut with a Swiss Army Knife. While they played she noticed a backpack, an item regularly stolen by orangutans in hopes of finding food. Unyuk made no immediate move for the pack – instead she continued to act out her role in the haircutting game, grabbing the hair on top of her head and inviting the assistant to continue playing as she gradually moved sidewise and closer to the pack. Once she had a free path, she lunged and made a grab for the unattended pack. (This was one of seven pantomimes that the researchers labeled as deceptive, where the actor feigned an inability, an interest or an intent in order to obtain help, distract, or express friendly intent and facilitate reconciliation.)

Russon and Andrews believe that some of the pantomime cases contain attributes of natural language:

including compositionality (large meaningful units are composed of smaller meaningful units…), systematicity (the actions and entities pantomimed are meaningfully rearranged following predictable patterns…) and productivity (…unique creations of the moment). Thus, orangutans can communicate content with propositional structure and have the kind of cognitive capacities with constituent structure typically associated with linguistic capacities.

Although spontaneous pantomiming appears to be fairly rare among orangutans (again, a total of 18 examples were unearthed from 20 years’ of data), the underlying data came from studies that were not focused on communication, and the researchers believe that other studies may have missed similar pantomiming to the extent that they focused on the functional aspects of gestures rather than the significance of pantomime as a medium for communication.

In any event, the study offers an eye-opening lesson in how sophisticated – to the point of being linguistic – non-verbal communication can be. If nothing else, we should not be too overconfident if we ever have a chance to play charades against a team of orangutans.

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¹Russon, A., & Andrews, K. (2010). Orangutan pantomime: elaborating the message Biology Letters, 7 (4), 627-630 DOI: 10.1098/rsbl.2010.0564.