Barbara J. King

Friday Animal Blog

How We Study Monkey and Ape Communication

March 11, 2011

This week is spring break for me. Before it began, I harbored hopes of novel-reading, co-basking in the sunroom with cats, going to movies with the family, in and amongst the midterm-grading and article-writing all of us do during “holiday weeks.” Thanks to an email I sent in late 2010, this heartwarming scenario has not come to pass.

Back then, I sent a yes, I’ll do it email that has come back to haunt me. Michael Ruse asked me to write a 5000-word entry on “language since Darwin” for the Cambridge University Press encyclopedia on Darwin that he’s editing. Another person had written an entry on Darwin’s own views on language, and my tasks would be to consider the last 50 years or so of language theorizing in a Darwinian light. At the time, it seemed like a fun challenge.

Well, I had it half right (the challenge part). I’m enjoying it well enough in a weird way, but it’s not precisely fun. I’m sifting through masses of articles on primate communication and the origins of language, trying to accept that compressing a topic of this magnitude into so few words will produce at best Swiss cheese- an entry with holes enough to annoy my colleagues whose work can’t be included.

I played around online this week and discovered a neonatal (days old!) entry in the relevant literature, an article at Animal Behaviour. Written by Katie Slocombe, Bridget Waller and Katja Liebal, it’s titled The language void: the need for multimodality in primate communication research. These three researchers take a hard look at primate studies published in the areas of vocalizations, gestures, and facial expressions, from 1960 to 2008 (overlapping considerably with exactly the time period I’m charged with analyzing).

Among their findings:

*Of 553 studies, the overwhelming majority (95%) focus on only a single communicative modality. The vocal mode was primary (64% of the studies), followed by facial expressions (22%) and gesture (9%).

*Research done in one modality tends to differ so much from that done in the others as to confound reliable comparison. Data on gestures tend to come from captive apes with a focus on behavior of the producer, for instance, whereas data on vocal calls tends to come from both wild and captive monkeys, with a dual focus on the producer and the receiver. (I prefer less linear terms in communication research than producer and receiver, but that’s a story for another day).

*The implications of the point just made are profound. In the literature, statements abound to the effect that gestural signals are deployed with intention and greater flexibility compared to vocal calls. However, most vocal studies concentrate on alarm calls whereas most gesture studies focus on relaxed behaviors like play. Evolutionary theory predicts that natural selection should tend to produce unambiguous signals in urgent contexts like predator defense, compared to non-urgent contexts—meaning that the stated comparison may be an artifact of the study framework.

*“It is not possible,” Slocombe et al. conclude, “to state unequivocally that gestures are more or less intentional than vocalizations, or that facial expressions are more or less emotional than gestures, and so on.” In the future, primatologists might work to close the gap in two ways: by seeking to carry out work in the comparatively neglected arenas of “vocal research in apes; gestural work in the wild; experimental facial work; and research on the receiver.” Further, multi-modality itself might become a central focus: “Abandoning the traditional distinctions between gesture, facial expression and vocalization could therefore have a large and positive impact on the study of language evolution.”

What a provocative boundary-smashing suggestion! It may prove profoundly difficult for the human brain to move beyond categories in this way. Still, the linguist Sherman Wilcox and his co-authors have long argued, speech is gesture (via movement within the vocal tract), and similar logic could be applied to facial expressions. With sophisticated techniques of audio and video analysis available to primate researchers nowadays, multimodality may increasingly become a topic of choice.

Equally provocatively, Slocombe et al. claim that we can’t explicitly identify components of language in other species, because language evolved uniquely in humans. Is this so, though? It’s not that I want to assert language exists in monkeys or apes, but rather that we do have evidence for things like referentiality, and meaning-making via recombining of signal units in syntactic ways, and dynamic negotiation of meaning. None of these alone amounts to language, but could any be considered a component of language? This question, I believe, should not be closed but rather, wide open.

As I’ve noted in other blog entries, there’s nothing like the rush of finding a terrific journal article to make one’s week—even spring break week!


  1. March 11, 2011 11:00 AM EST
    Great post! I really appreciate the concise overview of the data that exists on this topic and I will definitely read the Slocombe et al paper. Thanks for bringing it to my attention. It seems clear that human language, even, does not solely depend on vocalizations, so it is definitely important to investigate these other modalities in non-human primates. I'm thinking of ways to study gestures in the wild....
    - Laurie (@DrYapyapi)
  2. March 11, 2011 1:38 PM EST
    Thanks for this article!
    - altheakale
  3. March 11, 2011 2:58 PM EST
    Laurie, I'd love to hear what you come up with vis-a-vis planning studies on gesture in the wild. Since my 2004 book on the topic I've kept a hand in gesture research, but in captivity. My co-authors Marcus Perlman and Joanne Tanner and I have a book chapter coming out in a volume that looks to be wonderful, edited by Simone Pika and colleagues (probably 2012). Meanwhile, do you know Joanne Tanner's website? It's easily findable by googling; she has wonderful videos and links to her articles on gorilla gesture in captivity that I find very stimulating. And altheakale, thanks for the comment!
    - Barbara J. King
  4. March 12, 2011 9:58 AM EST
    It's a common expression that "so-and-so couldn't talk, if you tied her hands behind her back," and everybody knows from emails that tone and facial expression mean at least as much as the words, yet we don't apply that to other animals?
    - Marian Allen
  5. March 12, 2011 10:40 AM EST
    Hi Marian, great to hear from you! You ask a good question. Yes, those of us who study animals do take into account gesture and facial expressions, most definitely- there's a rich literature on this. Personally, I have tons & tons of videotapes strewn around my house and office, because I observed gesture behaviors in apes... But the strange thing is, that mostly, those of us who study gesture don't focus as much on vocalizations or on facial expressions, and those of us who study vocalizations don't... well, you get the picture. It's a kind of artificially divided plan of study, according to the authors of this new article. We hope to move collectively towards a more holistic approach!
    - Barbara J. King
  6. March 14, 2011 6:57 AM EDT
    I'm writing an essay on just this topic at the moment, but my heavily-arts-based Universtiy doesn't subscribe to Animal Behaviour... any chance you could send me a pdf? =)
    - Sarah
  7. March 14, 2011 11:59 AM EDT
    Hi Sarah - what university are you at (pure curiosity)? In fact a number of people have asked for a PDF. Normally I can do this, but for some reason the online system at my College isn't letting me download a PDF in this case. Perhaps because it is only available online and not yet in print? I am not sure. You could ask the lead author for a copy; Dr. Slocombe's email address is [Meanwhile I do hope your university library has a copy of my The Dynamic Dance!!]

    - Barbara J. King

Selected Works

Why are animals so irresistible to us? Why do we live with and care so deeply about them? From the famous "art caves" of ice-age Europe, to the ancient villages where animals were first domesticated, to stories of apes, whales, dogs, and cats doing fascinating things today, King weaves together a scenario about the animal-human bond that encompasses our past, present and future.
Can scientists discover a prehistory of religion just as they have traced the evolution of technology, language, and art? What does compassion in chimpanzees, or burial patterns in our human ancestors and Neanderthals, tell us about the origins of religion? In Evolving God, named a Top Ten Religion Book for 2007 by the American Library Association, Barbara King explores these questions.
How do chimpanzees, bonobos, and gorillas-- the African apes -- communicate using body postures and gestures? Using her many years of experience studying these apes, Barbara King answers this question in a book that offers a new perspective on the evolution of language.