How are humans able to act cooperatively and why don’t we see such behaviour in other primates? Jonathan Birch looks at the concept of “joint know-how”.

Humans vs. chimps

Think of a simple act of cooperation: two people pick up a sofa together, carry it into a room, and put it down on the floor. Simple though it is, this is an amazing thing: it’s something that sets us apart from all other primates.

As the primatologist Michael Tomasello once remarked, no pair of chimpanzees would ever do it. Not because they don’t have furniture, but because they don’t have the right kind of minds: they just don’t ever seem to act together in anything like the way we do. There’s debate as to whether sometimes, in some special circumstances, they do act in pairs or teams – but even if they do, it isn’t an ordinary, everyday, ubiquitous feature of their lives, like it is for us.

So what makes us different? How do our minds differ from theirs – in what ways are human minds wired for cooperation? This is, of course, a big question – one that spans cognitive science, primatology, philosophy, anthropology, linguistics and more. One smallish but important part of that question concerns what I call “joint know-how”.

When two people carry a sofa together, they show they know how to carry a sofa together. When two people dance together, without stepping on each other’s toes or appearing badly coordinated, they show they know how to dance together. When two people row a boat together, moving smoothly through the water without veering from side to side, they show they know how to row together. We can say all these pairs of people have a piece of “joint know-how”. There is something they know how to do together. They have the special type of knowledge that makes cooperation possible.

But what is joint know-how? I think philosophers should pay more attention to this question than they have done up to now. It matters if we want to understand how human cooperation works – and how it differs from the kinds of cooperation we find in the rest of the natural world.

Philosophers have, admittedly, been interested for a long time in “joint intentions”, like our intention to row together or dance together. But joint intentions are transient things, here one minute, gone the next, as soon as the activity is finished or abandoned. Joint know-how is the stable, persisting basis for joint intentions. It’s only because we already know how to dance together that we can, when the mood takes us, intentionally do it.

To get to grips with joint know-how, we need to think about the difference between two people who know how to do something together and two similar people who, for all their individual skill, just don’t. For example: what’s the difference between two singers who know how to sing a duet together and two singers whose individual singing is just as good, but who don’t know how to sing with each other? What’s the difference between two rowers who know how to row together, and two who are just as skilled as individuals but can’t row together in the same boat?

An intuitive starting point is that people with joint know-how don’t just know how to do their individual parts, but also know how to coordinate with each other as they do them. That’s true as far as it goes, but here we get to the heart of the puzzle: knowing how to coordinate is itself just another piece of joint know-how. We haven’t really explained what joint know-how consists in until we’ve explained that. So what’s the difference between two people who know how to coordinate and two people who don’t?

Active mutual enablement

In recent work, I’ve developed an answer to this question. My account of joint know-how – the “Active Mutual Enablement” or “AME” account – hypothesizes that knowing how to coordinate consists in each person having four different pieces of individual know-how at the same time:

First, each person knows how to monitor the behaviour of the other person, looking for signals and cues: signs that things are going well or starting to go wrong. Second, each person knows how to predict the behaviour of the other person from the signals and cues they observe. Third, each person knows how to adjust their own behaviour in light of what they’ve predicted, in such a way as to mitigate the risk of failure of the shared enterprise. Fourth – and most subtly – each person knows how to do their own individual part in a way that actively enables the other person to do the above three things. In other words, each person knows how to help the other person predict the emerging problems and risks that might call for adjustment.

The importance of all of these ingredients is easiest to see in an example. Imagine two skilled pianists playing a duet. A study by Goebl & Palmer in 2009 showed that, when forced to play in a noisy environment – so noisy they can’t hear the piano very well – skilled pianists will deliberately make big, exaggerated, up-and-down finger movements on the keys, so the other player can see where they are up to in the piece.

There is clearly monitoring, prediction and adjustment going on here, but there’s also active enablement: each player knows what it is the other needs to know, and knows they’ll be relying on sight in a noisy environment, so they naturally, almost “instinctively”, make their finger movements salient to each other (I say “instinctively” but, of course, it’s a learned skill, not strictly an instinct). The cognitive scientist Cordula Vesper calls this type of behaviour “coordination smoothing”.

It’s so easy to miss – but when you look for it, you realise this is a routine feature of acting together. Here’s another example. A rowing boat with two seats and one oar per person is called a “pair” (as depicted above in Thomas Eakins’ painting “The Biglin Brothers Racing”). Notoriously, it’s one of the hardest boats to row. Because the rowers only have one oar each, they need to stay perfectly in sync, or they will end up in the water. A study by Feigean and colleagues in 2017 showed that, when individually skilled rowers learn to row in a pair for the first time, the one setting the pace (in the stern seat) learns to become less variable, producing slower, larger-amplitude sweeps of the oar at a more regular rate than they did before.

This is all about actively enabling the other rower to monitor, predict and adjust to what they are doing. Of course, the other rower (in the bow seat) has to know how to be actively enabling too: they have to know how to signal any emerging problems to the person in front of them, telling them if they’re rowing too fast or too irregularly.

One important feature of any kind of know-how – joint or individual – is that you don’t have to use all of it all the time, in every single performance. Sometimes know-how can be latent: unused because everything is going so smoothly that no adjustment is actually needed. So, two people don’t have to be monitoring each other all the time to possess joint know-how. But they do have to know how to monitor, predict and adjust to each other when it matters – otherwise they’ll have no way of managing emerging risks and problems.

Humans vs. chimps revisited

Let’s return now to the big question: what makes humans different? Can chimpanzees have joint know-how too? No doubt, they can possess some of the important ingredients of joint know-how. They know how to adjust to the behaviour of others in activities such as hunting. However, I suspect something crucial is missing. I doubt they know how to actively enable each other to predict, monitor and adjust to their behaviour, like the pianists and the rowers in the above examples.

Why? Because this requires a capacity to understand how others are likely to respond to one’s own performance – what others will see, what they are able to predict, the inferences they are likely to make, and the ways they’re likely to adjust their behaviour in response. In other words, it requires a sophisticated capacity for “mind reading” or “theory of mind”, and I doubt chimpanzees have that.

I don’t think language is strictly needed, even though it’s one of the main ways in which humans actively enable each other’s cooperation. I can imagine joint know-how without any language. But what I can’t imagine is joint know-how without any understanding of each other’s thoughts. While it seems likely that chimpanzees have some basic capacity for theory of mind, even this remains a source of some controversy, and I don’t think it can be sophisticated enough to support active enablement of the type we see in pianists, rowers or even two people carrying a sofa, signalling to each other when a change of height or direction might be needed.

If this is right, then the evolution of joint know-how is part of the story of human evolution, and it post-dates our evolutionary divergence from the other great apes. It is entangled, in no-doubt complicated ways we’ve barely begun to explore, with the origins of human cooperation, language and theory of mind.

By Jonathan Birch

Jonathan Birch is an Associate Professor in the Department of Philosophy, Logic and Scientific Method, specializing in the philosophy of the biological sciences. Most of his work concerns the evolution of social behaviour. He is also interested in the evolution of morality, animal sentience, and the relation between sentience and welfare.