What Distinguishes Humans from Chimps? Vocal Learning and Ritual.

What Distinguishes Humans from Chimps? Vocal Learning and Ritual. November 9, 2019

No ritual for chimpsAlthough my online persona is a blogger who writes about religion, science, and culture, I’m also a researcher. (Read: I sit in an office tapping away on revisions hoping to please Reviewer 2.) My current research project is aimed at surveying and synthesizing the growing literature on cognitive, bio-cultural, and evolutionary approaches to religion. While this project mostly has me buried up to my nose in recent articles and books – published, say, within the last eight years – sometimes it’s useful to look backward and place more recent work in context. A short, fascinating paper from 2006 on the origins of music and ritual is a great example. In it, Swedish neuroscientist Björn Merker argues that vocal learning and an urge to conform are the keys to understanding how human and ape culture differ from each other – and that birds, of all animals, help pinpoint where this difference arises.

Both humans and other great apes – chimpanzees and bonobos, gorillas, and orangutans – have culture, defined as learned behavior that varies from group to group. Culture in nonhuman great apes is mostly limited to things like tool use; one band of chimps might have a technique for scooping up a snack of termites that differs from other bands’ techniques, for example. This is still culture, even if it doesn’t include museums, operas, or incessant internet bickering.

Marker draws a fascinating distinction, though, between apes’ instrumental cultures and the “ritual culture” of humans. By ritual culture, Merker means a socially learned system of behaviors whose form has no objective, instrumental connection to any practical outcomes. For example, if you insert a stick into a termite mound and withdraw it covered with delicious writhing termites, the goal (securing a meal) directly results from the actual physical properties of the stick and the sand. 

By contrast, if you kneel before the Queen to receive a knighthood, the sword she taps on your shoulder has absolutely no physical effect on you. Here, the sword isn’t a straightforward tool, like a hammer or a bucket. It’s part of a ritual, which only “works” when people do it properly. In practice, this usually means doing it the way others have done it before, step by step, according to protocol.

High-Fidelity Copycatting

Here’s the key distinction: for instrumental culture, innovation and improvisation are perfectly acceptable, even desirable, whereas for ritual culture they usually aren’t. According to Merker, 

Context-attuned performance flexibility is the hallmark of instrumental behavior…Literal duplication, however, lies at the heart of ritual behavior.

In other words, instrumental culture aims at practical goals, and whatever behaviors work will probably stick around and spread. Efficiency is absolutely paramount. On the other hand, ritual culture requires performing every little step, completing every motion, correctly, regardless of efficiency. Ritual isn’t concerned with physical causes and effects. You can’t rationally streamline the process of conferring a knighthood the way a factory manager streamlines an assembly process, because the entire ritual just is the way someone becomes a knight. Fastidiously copying others’ actions, recreating learned sequences of motions with absolute fidelity – these things define ritual culture.

And they’re precisely what other great apes don’t do. Developmental psychologists and evolutionary anthropologists have repeatedly shown that, while human children fastidiously copy every gesture and motion that an adult model performs, chimpanzees only copy the practical steps. They care about efficiency, but they lack the peculiarly human capacity for “over-imitation:” mimicking others with high precision, even seemingly irrelevant actions. As writers such as Joe Henrich have argued, this single variation in copying ability helps explain a whole lot of the wider-scale differences between our species, from humans’ far greater range of habitat to chimpanzees’ lack of recognizable music and dance.

A Notable Lack of Ape Guitarists

How do music and dance play into this?

Well, for all their humanlike qualities, chimps and other great apes lack music. They can transmit instrumental knowledge about tools, but they don’t make patterned, organized sound for recreational purposes, and they pretty much completely lack the ability to keep together in time, as in clapping or dancing. In fact, no other species seems to do these things together. You’ll never see chimps, gibbons, or monkeys – much less giraffes or beavers – dancing together to regular beats in groups, as humans do everywhere. 

Merker’s argument is that these unique human traits – the propensity for communal music and our proneness to ritual and over-imitation – are deeply entwined. Music, in his definition, is a kind of ritual, because it (a) has to be learned, mostly by imitation, and (b) serves no immediate practical function. Thus, only species that are primed to over-imitate – that is, to inhabit a ritual culture – could be expected to have music. 

Many other species have vocalizations, such as duck quacks or cats’ meows. But these are genetically inbuilt – they don’t have to be learned. By contrast, humans have to learn the languages they speak, as well as the musical tropes and techniques of their unique cultures. This makes us utterly unique among primates.

But we have some unexpected company elsewhere. Pinnipeds – seals, sea lions, and walruses – are vocal learners whose vocalization abilities remain plastic into adulthood. Many learn their calls during adolescence from nearby adults, with the result that calls differ between different groups of the same species, like dialects. Humpback whales, too, possess vocal learning, with different pods or geographically far-flung groups singing very different songs. 

Vocal Learning and Self-Conscious Chicks

But the most widespread vocal learning is in songbirds, a vast suborder that includes species as diverse as wrens, robins, and even crows.* These quick-witted avians are known for their vocal flexibility and creativity. Despite singing songs that are often unique to – and diagnostic of – their species, these birds don’t simply hatch from the egg with all the knowledge they need to sing those songs. Just like humans, seals, and whales, they have to pay close attention to the vocalizations of older individuals. Only slowly, with laborious practice, do they learn the skills and patterns that make it possible for them to replicate the standard song for their area. 

(Fun fact: songbirds spend large parts of their chickhood quietly babbling to themselves, effortfully learning to reproduce all the different tones and melodies that will eventually become their adult repertoire. They often go to some lengths to make sure they’re alone when singing these pre-adult “subsongs,” almost as if they’re self-conscious. Isn’t that cute?)

Now, for humans and other tool-using animals (such as chimpanzees and some songbirds) the motive to learn to use practical instruments is to accomplish practical ends. So individual animals take pains to copy others’ tool-use techniques only to the extent that it leads to successful practical outcomes. They don’t have to replicate every single aspect of an older animal’s stick grip. Instrumental culture, in other words, doesn’t require absolutely perfect imitation. It just calls for imitation that’s good enough.

But ritual culture calls for the extra mile. Learning a song takes a young songbird essentially its entire adolescence, because it’s trying very hard to get it exactly right – to memorize and replicate long, complicated phrases in just the right order. Similarly, learning language, music, or rituals takes humans more than just a casual amount of imitation. To learn language or music, we have to be able to copy each other very, very precisely.

Merker therefore takes vocal learning to be the common root of advanced copying abilities across species: animals that have vocal learning are excellent imitators, and those that don’t, aren’t. 

The Conformal Motive

One final piece of Merker’s puzzle is what he calls the conformal motive: an inbuilt drive to copy others and conform. We all know that humans have a conformist bias, but Merker highlights that such a bias is probably biologically necessary for vocal learning as well as for ritual and ritual culture, since there’s rarely an immediate practical reward for learning to copy ritualized actions or songs. 

Tool-using animals are motivated to learn tool use because they’re hungry and they want to get more termites. The reward is practical and nearby. But the reward for learning a song or a ritual sequence is usually less transparent, and often distant in time. It’ll be months and months before a baby robin can use its song to defend a territory or attract a mate. Similarly, if a human child faithfully learns to make the sign of the cross or kneel and stand for Muslim prayer, it’s not immediately clear what tangible advantage this sequence of actions offers her right then and there. Making the sign of the cross doesn’t fill your stick with termites, so to speak.

Of course, cognitive and evolutionary theories of religion suggest that there are practical rewards for partaking in ritual culture, from community support to heightened self-regulation. In fact, high-fidelity imitation and ritual may be what make us uniquely human, since they enable symbol-rich culture, division of labor, and abstract identities (such as “Egyptian” or “Catholic”). But because such benefits are usually far removed from any particular ritual action, evolution needed to come up with an internal reason to carefully observe and imitated others. This is what Merker calls the “conformal motive.” It’s a mechanism to keep us interested in duplicating others’ actions, even when the social rewards for doing so are many months, or years, in the future.

The Ritual Stance

Merker locates the distinction between ritual and instrumental behaviors at the cultural level. But more recently, scientists have described the cognitive dimensions of the same dichotomy using terms such as “ritual stance” and “instrumental stance.” In the instrumental stance, our minds interpret others’ behavior as practical attempts to change things in the physical world. When we take the ritual stance, though, we assume that there’s a normative or quasi-moral reason behind someone’s actions. We imitate rituals because we feel that we ought to.

So while Merker thinks that high-fidelity imitation, as in vocal or ritual learning, emerges from an intrinsic conformist motivation, more recent studies suggest that it’s specifically the desire to obey social norms – to be a good person – that drives humans to copy others so carefully. For example, developmental psychologists have found that children think over-imitation is the “right” thing to do. If this is true, though, does it mean that birds, whales, and seals also feel a normative pressure to copy the songs they hear? This seems unlikely, so it might be that Merker’s “conformal motive” simply takes a normative or moral tone in human beings. 

To wrap up, what’s useful about Merker’s paper is the way it brings a behavioral biology perspective to a topic – ritual and over-imitation – that’s more recently been dominated by cognitive-science approaches. This helps us to appreciate how deeply human cognition and social behavior are informed by evolutionary history, something we can’t truly understand without paying attention to behavior. It also sheds light on just why music is so unique and unusual in the animal world, and why we often lump it in the same category as ritual: music and ritual both require a very rare combination of high-fidelity imitation skills, vocal learning, and conformist or normative biases. Human ritual also usually deploys combinatorial, symbolic language, which only humans possess, as far as we know. Music, in turn, additionally requires specialized cognitive adaptations for timekeeping and rhythm – which I didn’t discuss here, but which seem most highly developed in species with vocal learning, including birds. Paradoxically, we share these core “human” abilities more in common with robins, crows, and cockatoos than with our very closest relatives. 

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* Yes, despite their distinctly unmusical, guttural howl, crows are technically “songbirds.” This is similar in principle to the way that Matchbox Twenty technically makes “music,” but only technically. 

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Photo credit: dsg-photo.com. Creative Commons license.

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