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\title {Origins of Mind: Lecture Notes \\ Acting Together }

\maketitle

# & Acting as One

\def \ititle {Origins of Mind}
\def \isubtitle {Acting Together }

\

\begin{center}
{\Large
\textbf{\ititle}: \isubtitle
}

\iemail %
\end{center}
Humans often act together, and less often they act as one.
My broad aim is to understand what might be involved in our acting as one, and what the consequences of our ability to act as one might be.
Let me start by clarifying the contrast between acting together and acting as one.

\section{Joint Action vs Parallel but Merely Individual Action}

\section{Joint Action vs Parallel but Merely Individual Action}

The tiny leaves blocked the drain.

Imagine some tiny leaves fall into your drain, blocking it. The tiny leaves block the drain together. This is not a matter of any one tiny leaf blocking your drain; rather, it is a matter of blocking being a common effect of the leaves’ behaviour.
Compare a case involving action.

1. The parents blocked the street.

+common effect

Two parents dropping off their kids at school by car may block a street by virtue of each independently attempting to execute a complementary turn.
They are acting together in the same sense that the tiny leaves are blocking your drain: their actions have a common effect.
Clearly this is not a case of acting as one. But what is missing? One missing feature is coordination, so let’s add this in.

2. The parents ensured no shots were fired (Mexican standoff).

One upshot of the Mexican standoff is that no shots are fired. Preventing a shot from being fired is somthing that the parents do together.

+common effect +coordination

And it is not only a common effect of their actions: it also depends on their being tightly coordinated. (If one looses concentration for even a moment, she will die.)
Now we have coordination as well as a common effect. But still this is clearly not a case of acting as one. What is missing? Could it be intention?
*example: Ayesha and Beatrice must each intend that they ...
\textbf{Simple Account}

Two or more agents act as one when there is an act-type, φ, such that each of several agents intends that they, these agents, φ together and their intentions are appropriately related to their actions.

3. The parents intended that they, the parents, walk together.

+common effect +coordination +intention

Counterexample to the Simple Account.
Contrast two friends walking together in the ordinary way, which is a paradigm case of collective agency, with a situation where two gangsters walk together but each is forcing the other. It works like this: Gangster 1 pulls a gun on Gangster 2 and says: “let’s walk” But Gangster 2 does the same thing to Gangster 1 simultaneously. This is walking together in the Tarrantino sense, and clearly not a case of joint action. At least it’s not joint action unless the central event of of Reservoir Dogs is also a case of joint action.
Since in this case there is something which all the agents involved intend, it seems that our acting as one can't be a matter only of there being something such that we each intend that we do it together.
What more is involved in acting as one? Bratman offers sufficient conditions for us to exercise shared agency in terms of our having a shared intention. His idea is, in essence, that we can get from merely intentionally acting together to exercising shared agency just by adding intentions and knowledge ...

\section{Bratman on Shared Intention}

\section{Bratman on Shared Intention}
Bratman’s brilliant idea for avoiding this sort of problem is to suggest that we don’t just each intend the action but rather we each intend to act by way of the other's intentions.
We can put this by saying that our intentions must interlock: mine specify yours and yours mind.
Now this appeal to interlocking intentions enables Bratman to avoid counterexamples like the Tarantino walkers; if I intend that we walk by way of your intention that we walk, I suppose can't rationally also point a gun at you and coerce you to walk.

‘each agent does not just intend that the group perform the […] joint action.

‘Rather, each agent intends as well that the group perform this joint action in accordance with subplans (of the intentions in favor of the joint action) that mesh’

(Bratman 1992: 332)

each agent does not just intend that the group perform the […] joint action. Rather, each agent intends as well that the group perform this joint action in accordance with subplans (of the intentions in favor of the joint action) that mesh' \citep[p.\ 332]{Bratman:1992mi}.
Our plans are \emph{interconnected} just if facts about your plans feature in mine and conversely.
‘shared intentional [i.e.\ collective] agency consists, at bottom, in interconnected planning agency of the participants’ \citep{Bratman:2011fk}.
In making this idea more precise, Bratman proposes sufficient conditions for us to have a shared intention that we J ... ... the idea is then that an intentional joint action is an action that is appropriately related to a shared intention.

We have a shared intention that we J if

‘1. (a) I intend that we J and (b) you intend that we J

‘2. I intend that we J in accordance with and because of la, lb, and meshing subplans of la and lb; you intend [likewise] …

‘3. 1 and 2 are common knowledge between us’

(Bratman 1993: View 4)

\begin{minipage}{\columnwidth}
\emph{Bratman’s claim}. For you and I to have a collective/shared intention that we J it is sufficient that:
\begin{enumerate}[label=({\arabic*}),itemsep=0pt,topsep=0pt]
\item (a) I intend that we J and (b) you intend that we J;
\item I intend that we J in accordance with and because of la, lb, and meshing subplans of la and lb; you intend that we J in accordance with and because of la, lb, and meshing subplans of la and lb;
\item 1 and 2 are common knowledge between us' \citep[View 4]{Bratman:1993je}
\end{enumerate}
\end{minipage}
Note that these conditions are sufficient but not plausibly necessary. If sharing a smile is a joint action, and if human infants in their first year of life are incapable of knowing things about other's knowledge of their intentions about the other's intentions, then to suppose that these conditions were necessary would be to imply that you can't share a smile with an infant. For this sort of reason, some have suggested that Bratman is right about one form of shared agency, but that there are other, less demanding forms of shared agency (Tollefsen, Pacherie). I think Bratman himself is coming around to the view that this might be right. I used to think this too, but recently I’ve come to the view that Bratman is more fundamentally wrong about shared intention.
In this talk I'll give a counterexample to Bratman's claim that these conditions, (1)--(3), are collectively sufficient for shared intention. My aim in doing this is to highlight an ingredient missing from Bratman’s and others’ accounts of shared intention. To anticipate what I'll explain later, Bratman focuses on interlocking intentions and interconnected planning. But in some or all cases it is not sufficient that our intentions interlock: in some cases, intentional joint action requires that we each make a single plan for our own and each other’s actions. This means taking a perspective that allows us to see our actions, yours and mine, as having a kind of practical unity. Or so I aim to show.
But first the counterexample.
In constructing the counterexample I shall exploit a feature of Bratman's account.
Needed to avoid circularity ... so this has to be neutral wrt shared intentionality.
It's also important, for Bratman's account and for my purposes, that I can intend *unilaterally* that we J. That is, I can intend that we J without depending on your also intending that we J.
Use ‘blocking the aisle’ as an example an action that can, but needn’t be, an exercise of shared agency. There are two people ahead of us on the train. They are blocking the aisle. We don’t know whether they are doing this intentionally or accidentally, nor whether their doing this is an exercise of shared agency or not. But still we can decide, in a sufficiently perverse mood, we shall do what they are doing. We can decide this without knowing whether what they are doing is an exercise of shared agency or not. The thing we are deciding to perform is an act-type that is neutral with respect to shared intentionality. Now this has a consequence that will be important for me. It means that one of us can intend that we J unilaterally, that is, irrespective of what the other intends. Suppose I know that you are going to stand where you are standing whatever I or anyone else does. You are rooted to the spot. Then I can decided that we will block the aisle, and I can decide this unilaterally because I know that you will do your part despite having no such intention.
This is the key to the possibility of UNSHARED INTENTION ...

\section{Counterexample to Bratman}

\section{Counterexample to Bratman}
The conditions for unshared intention are just like those for shared intention except that they concern two distinct activities, J1 and J2.
So for you and I to have an unshared intention that we , ...
If it is possible for Bratman's sufficient conditions for shared intention to be met without relevant irrationality or ignorance, then it is likewise possible for these conditions on unshared intention to be met.
\begin{minipage}{\columnwidth}
We have an \emph{unshared intention} that we <J$_1$, J$_2$> where J$_1$$\neq$J$_2$ just if:
\begin{enumerate}[label=({\arabic*$^\prime$}),itemsep=0pt,topsep=0pt]
\item (a) I intend that we J$_1$ and (b) you intend that we J$_2$
\item I intend that we J$_1$ in accordance with and because of la, lb, and meshing subplans of la and lb; you intend that we J$_2$ ...
\item 1 and 2 are common knowledge between us.
\end{enumerate}
\end{minipage}
Our individual subplans concerning our <J$_1$, J$_2$>-ing \emph{mesh} just in case there is some way I could J$_1$ and you could J$_2$ that would not violate either of our subplans but would, rather, involve the successful execution of those subplans.

We have an unshared intention that we <J1, J2> iff

‘1. (a) I intend that we J1 and (b) you intend that we J2

‘2. I intend that we J1in accordance with and because of la, lb, and meshing subplans of la and lb; you intend [likewise] …

‘3. 1 and 2 are common knowledge between us’

We have a shared intention that we J if

‘1. (a) I intend that we J and (b) you intend that we J

‘2. I intend that we J in accordance with and because of la, lb, and meshing subplans of la and lb; you intend [likewise] …

‘3. 1 and 2 are common knowledge between us’

(Bratman 1993: View 4)

Here is an example of two people who have an unshared intention.
Ayesha and Ahmed. They can each tilt the table, but only along one axis.
(Note that Ayesha can unilaterally intend that they, Ayesha and Ahmed, make the ball hit the red square.)

If you think Ayesha and Ahmed are having a bad hair day, you should see Beatrice and Baldric ...
Now explain that Ayesha and Ahmed have an unshared intention, but Beatrice and Baldric have a shared intention.
I claim that Beatrice and Baldric have a shared intention that they J$_1$ only if Ayesha and Ahmed have a shared intention. This claim follows from the similarities of the two cases. The only difference is that Beatrice and Baldric happen to have same task, whereas Ayesha and Ahmed have different tasks. But neither Beatrice nor Baldric makes use of the fact that they have the same task. So if we consider how Beatrice and Baldric's case differs from Ayesha and Ahmed’s, we can see that these differences do not plausibly amount to a difference with respect to shared agency. Shared intention cannot feature in one case but not the other.
This is a bit delicate. I am supposing that Beatrice and Baldric are each making use of the fact that Beatrice intends J1 and of the fact that Baldric intends that J2, but that they are neglecting to make any use of the fact that J1=J2.
So the only difference is that Beatrice and Baldric happen to have same task, whereas Ayesha and Ahmed have different tasks. But neither Beatrice nor Baldric makes use of the fact that they have the same task.
Beatrice does rely on the fact Baldric intends that they J1, of course; but she does not rely on the fact that what Baldric intends is what she intends.

 true? A&A make use of? Ayesha intends J1 ✓ ✓ Ahmed intends J2 ✓ ✓ J1=J2 ✗ ✗

 true? B&B make use of? Beatrice intends J1 ✓ ✓ Baldric intends J2 ✓ ✓ J1=J2 ✓ ✗

So I take this case to be an objection to the idea that we can explain acting as one by appeal to shared intention if we also accept Bratman's claims about what is sufficient for shared intention.

Simple Account

Two or more agents act as one when there is an act-type, φ, such that each of several agents intends that they, these agents, φ together and their intentions are appropriately related to their actions.

We have a shared intention that we J if

‘1. (a) I intend that we J and (b) you intend that we J

‘2. I intend that we J in accordance with and because of la, lb, and meshing subplans of la and lb; you intend [likewise] …

‘3. 1 and 2 are common knowledge between us’

(Bratman 1993: View 4)

So I reject two attempts to say what is involved in acting as one. The Simple Account fails because it is possible to meet this condition while walking in the Tarantino sense, and the Bratman-esque Shared Intention Account fails because it’s possible to meet these conditions in a situation where you are merely treating others’ intentions as opportunities to exploit and constraints to work around.
Acting as one requires more than this (and perhaps less than this too). But what is missing?
The problem I think is that we are failing to capture the agents’ perspective. Acting as one is in part a matter of how things seem to the agent. It is also, I think, partly a matter of the agents exploiting the fact that they each intend the same thing, or that their actions have a collective goal. But how can we get from such an intuition to a theoretical account of acting as one?

\section{Parallel Planning}

\section{Parallel Planning}

Parallel Planning

What’s wrong with B&B is that they don’t conceive of their actions as an exercise of shared agency.
What we want is some way to capture the sense that agents engaged in shared agency conceive of their actions as exercises of shared agency, without of course going in a circle by appealing directly to shared agency here.
At this point it’s tempting to appeal to romantic notions of sharing, or to introduce distinctive ingredients like special modes of thought, special ontological constructs or special kinds of reasoning. I want to suggest a way of capturing the agents’ perspective without any such distinctive ingredients. This is where parallel planning comes in. Let me explain ...

See also Raul Hakli & Pekka Mäkelä, ‘Planning in the We-­mode’ (in preparation)

A representation or plan is \emph{agent-neutral} if its content does not specify any particular agent or agents; a planning process is agent-neutral if it involves only agent-neutral representations.
Practical vs theoretical reasoning: ‘The mark of practical reasoning is that the thing wanted is \emph{at a distance} from the immediate action, and the immediate action is calculated as a way of getting or doing or securing the thing wanted’ \citep[p.\ 79]{Anscombe:1957ln}. See also \citet[p.\ 1]{millgram:2001_practical}: ‘Practical reasoning is reasoning directed towards action: figuring out what to do, as contrasted with figuring out how the facts stand.’
Some agents each \emph{individually make a plan for all the agents' actions} just if: there is an outcome; each agent individually, without discussion, communication or prior arrangement, plans for that outcome; and each agent’s plan specifies roles for herself and all the other agents.
Our planning is \emph{parallel} just if you and I are each planning actions that I will eventually perform and actions that you will eventually perform, where the resulting plans non-accidentally match.
Two or more plans \emph{match} just if they are the same, or similar enough that the differences don't matter in the following sense. First, for a particular agent's plan, let the \emph{self part} be those steps concerning what will be the agent's own actions and let the \emph{other part} be the other steps. Now consider what would happen if, for a particular agent, the other part of her plan were as nearly identical to the self part (or parts) of the other's plan (or others' plans) as psychologically possible. If the agent's self part would not be significantly different, let us say that any differences between her plan the other's (or others') are not relevant for her. Finally, if for some plans the differences are not relevant for any of the agents, then let us say that the differences don't matter.
The guiding idea behind Bratman's conditions for shared intention is this:
shared agency consists, at bottom, ...

shared intentional agency consists, at bottom, in interconnected planning agency of the participants.’

(Bratman 2011, p. 11)

We have a shared intention that we J if

‘1. (a) I intend that we J and (b) you intend that we J

‘2. I intend that we J in accordance with and because of la, lb, and meshing subplans of la and lb; you intend [likewise] …

‘3. 1 and 2 are common knowledge between us’

(Bratman 1993: View 4)

parallel planning

You plan our actions, yours and mine, and I plan our actions too

Here, interconnected planning is planning where facts about your plans feature in my plans & conversely. What I've just tried to show is that interconnected planning is not sufficient for joint action. Ayesha's and Ahmed's plans are interconnected and so are Beatrice's and Baldric's, but still each sees the other's actions only as opportunities to exploit and constraints to work around. Now my question is what would be sufficient for joint action ...
Suppose you and I are tasked with moving this table through that door.
In doing this, must my plan take into account facts about your intentions as well as about the weight of the table, width of the door &c?
This case has some special features: (i) there is a single most salient route for the table given our objective; (ii) there is a single most salient way of dividing up the roles between us.
I suggest that, in this situation, neither of us needs to form a plan involving the others' intentions.
The situation makes this redundant.
All we have to plan is how two people in our situations should move the table through the door.
To a first approximation, then, what the situation seems to call for is not that our plans are interconnected but rather that we each make a plan for the table-moving action as a whole. This is inspiration for the view that we might arrive at sufficient conditions by reflecting on parallel rather than interconnected planning ...

shared intentional agency consists, at bottom, in interconnected planning agency of the participants.’

(Bratman 2011, p. 11)

parallel planning

You plan my actions as well as yours, and I do likewise.

In parallel planning, I plan all of our actions and you do the same.
I want to suggest that shared agency sometimes requires only parallel, and not interconnected planning.
Some of you are probably already thinking that the very idea of parallel planning is incoherent, and I will face up to this objection.
But first I want you to suspend disbelief and consider how parallel planning could enable us to coordinate our actions and our plans ...
Suppose you and I are parents about to change our baby's nappy.
This involves preparing the baby and preparing the nappy.
You're holding the baby and I'm nearest the pile of clean nappies, so there's a single most salient way of dividing the task between us.
Preparing the baby is, of course, a complex action ...
Now there are relational constraints on how the baby and nappy should be prepared; how you clean constrains and is constrained by how I prepare the clean nappy (because we don't want to get pooh on it).
\textbf{How do we meet these relational constraints?} The fact that I have a plan for the whole thing and so do you, and the fact that these plans are identical or similar enough that the differences don't matter means that your plan for your actions is constrained by your plan for my actions, which is my plan for my actions. So thanks to our parallel planning---to the fact that we each plan the whole action---your plan for your actions is indirectly constrained by my plan for my actions; and conversely. So: in parallel planning, we meet these relational constraints not by thinking about each other's intentions but by planning each other's actions.
There's just one tiny problem. In supposing that we both make a plan for the whole action, I'm implying, of course, that we each make plans for actions that are not our own. And this seems incoherent, unless perhaps we (the agents performing the action) are irrational or ignorant. It seems incoherent because the elements of plans we make are intentions; so, apparently, in making a plan for your action I would end up intending your actions. But I can't intend your actions, I suppose. What can we do?

agent-neutral practical deliberation

But what attitude results from practical deliberation?

open-ended intentionsTo solve this dilemma we need to appeal to some ways in which intentions can be open-ended.: whatIt's a familiar idea that intentions can be open-ended with respect to what is intended.For instance, you can intend to visit the Weinachtsmarkt without intending to do so on any particular day., and whoIt's also true that intentions can be open-ended with respect to who will act on them.Consider a couple planning some tasks at the start of the weekend: they need to buy bread, to clean the bath, ... At this point, their intention is that one or both of them will do each of these things, but there is no further specification concerning who will act. Now you might say that you can't intend something without settling who will act. But this seems wrong given that (i) the couple's attitudes are practical, and (ii) generate requirements concerning agglommeration. (Even before it's determined who will do what, I know that I'm not going to be able to spend the afternoon in the pub.)[*skip] You might also say that open-ended intentions generate pressure to filling in details. This is true, but the details are not always filled by further intentions. At some point intentions give out and we just act. The point of appealing to the table-moving example was that here there is no need for the intention to specify the agents.I want to suggest that appeal to the open-endedness of intentions will help with the dilemma I had.The problem was, what attitude could I have to another's actions?

The attitude I can have is this: with respect to the whole plan, I intend that we implement it.
And with respect to its components, I intend that you or I or we do it.
So my intentions don't specify who will do what.
But they don't need to, because this is already adqeuately specified by the fact that you're holding the baby and I'm nearest the clean nappies.
So in this case what determines who does what are the constraints, not the intentions.

shared intentional agency consists, at bottom, in interconnected planning agency of the participants.’

(Bratman 2011, p. 11)

parallel planning

You plan my actions as well as yours, and I do likewise.

This is why, despite appearances, I think the notion of parallel planning is coherent. Without irrationality or ignorance, it is possible for us each to plan all of our actions, yours and mine, and to act on these plans. In doing so we achieve coordination and manifest collective intentionality not by thinking about each other's plans but, more directly, by planning each other's actions.
Let me return for a moment to the Tarantino walkers and what I was calling the Simple Account of shared intention. According to the Simple Account, we have a shared intention that we walk just if we each intend that we, you and I, walk. Now, as you may recall, earlier I noted that this seemed not sufficient because we might have and act on such intentions while forcing each other to walk at gunpoint. It is this problem that Bratman uses to invoke interconnected planning. But actually we can see that the problem can also be overcome by invoking parallel planning.
Consider the view that for us to exercise shared agency in walking together it is sufficient that: \begin{enumerate} \item we each intend that we, you and I walk; \item we pursue these intentions by means of parallel planning (that is, we each plan all our actions and our plans match); and \item we each end up with open-ended intentions concerning the components of our plans. \end{enumerate}
This view rules out the Tarantino walkers (who each point a gun at the other) because pursuing an intention by means parallel planning means taking a practical attitude towards each other's actions. So, if my conditions are met, your pointing a gun at me would be almost like your pointing a gun at yourself in order to force yourself to do something you intend.
[*skip] One more thing about interconnected and parallel planning. Earlier I noted that interconnected planning is demanding in two respects: it's demanding with respect to which mechanisms can underpin shared agency, and with respect to which agents can exercise shared agency. By contrast, parallel planning is not demanding in these respects. In parallel planning, I don't make plans about your plans, I simply plan your actions. So it does not demand mechanisms which are capable of meta-planning, nor agents capable of understanding and thinking about others' plans. Recognising a role for parallel planning in shared agency may thus allow us to understand exercising shared agency might not presuppose deep insights into the nature of minds, and so tempt us to consider the conjecture that it is through acting together that we first come to understand other minds. But that is another talk ...
Now so far I've been arguing only that (i) the notion of parallel planning is coherent, (ii) that parallel planning enables us to coordinate our actions, and (iii) that appeal to parallel planning might be useful for explaining shared agency because it gives us a way of ruling out some counterexamples. But that doesn't, by itself, amount to showing that the notion of parallel planning can is any more useful than that of interconnected planning. For all I've said so far, it might be that both parallel and interconnected planning play a role in corrdinating actions, but neither can be used to give sufficient conditions for intentional joint action. Can I do better?

parallel planning yields practical unity

Earlier I suggested that interconnected planning can't be what shared agency at bottom consists in because agents can have interconnected plans while thinking of each other's actions only as opportunities to exploit and constraints to work around, and so without conceiving of themselves as exercising shared agency.
Now I want to suggest that in parallel planning, we take a perspective that allows us to see our actions, yours and mine, as having a certain kind of practical unity.
To illustrate, first consider the case of a single individual.
Imagine someone committed to keeping two or more areas of her life apart, so that she tries to plan separately for each area of her life. When concerned with planning in one area, she treats ongoing and planned actions from other areas of her life almost as if they were the actions and intentions of another agent who is temporarily acting with her body. Actions from other areas of her life feature in her current planning only as constraints to work around or opportunities to exploit. Of course, many of her predictions about her own actions are based on plans she has made when thinking about other areas of her life. But she systematically avoids conceiving engaging in planning for actions that involve different areas of her life; she does not treat her actions as even potentially parts of a single, larger plan. So there is a kind of practical unity that she fails to conceive of the actions which make up her life as having. She never takes perspective one has on actions when engaged in planning for them with respect to all her actions. Instead, at each time she plans for just one area of her life and takes the perspective of an outsider on the other areas of her life.
As this illustrates, the ability to conceive of any our actions as potentially featuring in a single planning process matters partly because it allows us to see them as having a kind of practical unity.
This applies to how you conceive of others' actions, not just your own. Earlier, I argued that you can sometimes engage in practical reasoning for not only actions you yourself will eventually perform but also for actions that others will eventually perform. This shows that it is sometimes possible to take the sort of perspective on others’ actions that you would paradigmatically take on your own actions. %***thanks to Peter Fossey here: I am not suggesting, of course, that you thereby conceive of others’ actions exactly as if they were your own. But nor do you conceive of the others’ actions in quite the way you would conceive of the actions of just any other agent who happened to be passing by. Rather, you conceive of these actions as on a par with your own actions insofar as they all feature in a single planning process.
This is why it's plausible that we can give sufficient conditions for acting as one by invoking parallel planning

Simple Account

Two or more agents act as one when there is an act-type, φ, such that each of several agents intends that they, these agents, φ together and their intentions are appropriately related to their actions.

We have a shared intention that we J if

‘1. (a) I intend that we J and (b) you intend that we J

‘2. I intend that we J in accordance with and because of la, lb, and meshing subplans of la and lb; you intend [likewise] …

‘3. 1 and 2 are common knowledge between us’

(Bratman 1993: View 4)

We can save the Simple Account. The mistake was to think that we should add more intentions on top.
Instead I think the key is understanding how intentions lead to action.
Parallel planning gives us an account of how the intentions have to be related to the actions.
Is this all? No way! I don't think we have begun to understand the experience involved in acting as one. One way to bring this out is to think about very small-scale cases of acting as one. ...
In a 2011 paper, Olle Blomberg suggested that we can understand something as one by understanding how agents represent their bodies.
I think we can extend and generalise this idea by turning from intention to the motor representations that underpin acting as one. But this is another story. For now what I hope to have shown is that we can't capture acting as one by appeal to the kinds of structure that Bratman discusses, and that parallel planning is probably a necessary ingredient in understanding what it is to act as one.
Sometimes interlocking intentions and knowledge states are not enough. Sometimes no amount of forming intentions about others’ intentions and acquiring knowledge of such intentions is sufficient, all by itself, for shared intention. In some or all cases, joint action requires changing perspective to conceive of your own and others’ actions as the upshot of a single planning process.
This matters for understanding why many of us see joint action as important in our lives \citep[compare][p.\ 327]{Bratman:1992mi}. In exercising ordinary, individual agency, we sometimes take a perspective that allows us to see our own temporally scattered actions as having a kind of practical unity. Relatedly, exercising shared agency sometimes involves taking a perspective that allows us to see our actions, yours and mine, as having a somewhat similar unity. It is not just that our individual plans mesh. It is that we plan almost as if you and I were one. In exercising shared agency we two are practically one.

acting as one

I think the phrase ‘acting as one’ could be misleading. What is as one?
From the point of view of the agents, it is not a matter of there being one agent or many agents. My suggesting is that practical deliberation and intention are, in the most basic cases, indifferent as between one and two agents acting. The question of who is acting can be left open at the start and is eventually settled by the world rather than by a decision on our part. There is nothing you need to add to intention to get shared intention.
So ‘as one’ does not refer to our being one. We aren't one and we aren't many because we aren't yet in the picture at all. Rather the suggestion is that acting as one is a matter of us conceiving of our actings as having a certain kind of unity.

Any evidence for parallel planning-like motor processes?

1. Each represents a single outcome motorically, and
2. in each agent this representation triggers planning-like processes
3. concerning all the agents' actions, with the result that
4. coordination of their actions is facilitated.
What do we need? (i) Evidence that a single outcome to which all the actions are directed is represented motorically. (ii) Evidence that this triggers planning-like processes, (iii) where these concerning all the agents' actions, and (iv) the existence of such representations facilitates coordination of the agents' actions.

Kourtis et al (2014, figure 1c)

I think we're a long way from having a large body of converging evidence, but there is some that points in this direction. One of the most relevant experiments is this one by \citet{kourtis:2014_attention}.
They contrasted a simple joint action involving two agents clinking glasses.

Kourtis et al (2014, figure 1c)

Kourtis et al (2014, figure 1c)

joint

individual-bimanual

individual-unimanual

## Sharing a Smile

\section{Sharing a Smile}

\section{Sharing a Smile}
[THIRD POINT: smiling is a goal-directed action, the goal of which is to smile that smile]
My topic is sharing a smile. But first think about ordinary, individual actions like genuine smiles.
What distinguishes a genuine smile from a muscle spasm or the exhalation of wind?
I want to suggest that it's this: the smile is a goal-directed action where the goal is to simile that smile.
But why think of the smile as goal-directed? Because smiling the smile requires considerable motor coordination: it’s not a matter of simple muscle contractions but more like the production of a phonetic gesture where context affects what is needed to realise the smile.
Further, like grasping an object or articulating a particular phoneme, it is an action that can be realised by different bodily movements in different contexts.
This is why I put slides of two quite different but both genuine smiles.
[Objection:]
Now you might say that the smile can't be goal-directed because is isn't explicable by appeal to belief, desire and intention
This is because the genuine smile is spontaneous and not something that can be produced at will (although it could probably be inhibited, at least to some extent); after all, this is what distinguishes the genuine from the polite smile.
\footnote{
From web source: The Duchenne smile involves both voluntary and involuntary contraction from two muscles: the zygomatic major (raising the corners of the mouth) and the orbicularis oculi (raising the cheeks and producing crow's feet around the eyes). The zygomatic major can be voluntarily contracted but many people can't voluntarily contract the orbicularis oculi muscle.
}
So now we might be tempted by the view that a smile is merely caused by an emotion in the way that gasses can cause you to burp.
Maybe there are smiles like this, but some genuine smiles are sustained.
And what sustains them is a process of controll
How could this be if such smiles are not consequences of beliefs, desires and intentions?
I think a reasonably natural view here is to think that part of what makes an event a smile, a goal-directed action and not just a muscle spasm caused by excess wind, is the way that motor control is involved. Specifically, the genuine smile will involve a motor representation of the outcome, the smile, and this motor representation will lead to movements by way of planning-like motor processes.
But you don't have to buy this to agree with me.
All you have to accept is that actions like some smilings can be goal-directed and controlled even in the absence of relevant beliefs, desires and intentions.
I think smiles fall into the category of actions like graspings, reachings and gesturings which are goal-directed but do not necessarily involve intention.

So far, then, I've suggested that smiling is a goal-directed action, the goal of which is to smile that smile.
Now imagine a situation where a single individual encounters and event (a clown’s falling) which causes amusement which causes her to smile
Note that the smile also modulates the emotion; if, for example, she supressed the smile, the quality of her amusement would change.
How could we gain insight into the fine-grained dynamics of others’ emotions?
How could we ever appreciate the unfolding of another’s grief, or the way their engagement leads to an explosion of ecstasy at the climax of a concert?
Part of the answer is obvious: by being there, with them.
[Not that this is the only possibility --- in some cases we might be told.]
But how exactly does being there, in the same situation help?
Merely being in the same situation is surely not enough.
It’s not enough that we each experience amusement, grief or ecstasy.
After all, individuals are different. Different individuals’ feelings don’t unfold in the same way just because they are in the same situation.
It’s just here that collective intentionality is relevant.
\textbf{What is involved in sharing a smile?}
Minimally, I think there have to be two kinds of connection between us for us to share a smile.
First, the way your smile unfolds is shaped by how mine unfolds and conversely.
I also suppose that our smiles can be minutely coordinated with each other.
But it’s not just that our smiles are interdependent in this way ...
It’s also that each of our smiles is shaping the way our amusement unfolds.
So the way your amusement unfolds is being controlled by, and controlling, the way mine unfolds.
In sharing a smile, we are emotionally locked together.
[*todo: remove motor stuff for this talk! Also: don't lose sight of idea that control is a way of knowing.]
[*todo: need slide with control arrows highlighted (my emotion controls yours).]
[*Structure: (i) I know because my emotion controls yours; (ii) But if my emotion controls yours, how can yours be amusement at the clown's falling? because control is partial, and reciprocal; (iii) But the mere fact of control isn't enough for knowledge; rather, control must show up in experience somehow. After all, for all I have said so far, we might, in sharing a smile, be unaware that our emotions are locked together. (iv) There must be an experience that is distinctive of sharing a smile. (iv) Note that I don’t want to say that someone who is sharing a smile needs to understand the situation in the way I’m describing it. All I'm claiming is that the fact of reciprocal control somehow affects our awareness. (v) It may affect in our awareness insofar as we are sensitive to contingencies between our own actions' and others' actions, and between our actions and the causes of them. (vi) So my position is this: the reciprocal control justifies each agent in making judgements about how the others' amusement is unfolding, and this justification is at least indirectly available to the agents by virtue of their having experiences characteristic of sharing a smile. ]
Our being emotionally locked together means that to a significant extent I am feeling what you are feeling, that the way my amusement is unfolding matches they way your amusement is unfolding. So if you know how your own amusement is unfolding and you know that we are emotionally locked together, you can know much about how my amusement is unfolding. So joint expressions of emotion like sharing a smile have the potential to enable us to know not just that others are amused but how their amusement is unfolding.
But the fact of reciprocal control (which means our emotions are locked together) together doesn’t all by itself mean that we can know how each other’s emotions are unfolding. After all, for all I have said so far, we might, in sharing a smile, be unaware that our emotions are locked together. Now you might think this sounds implausible because its hard to imagine sharing a smile without an experience that is distinctive of sharing a smile. And it might be natural to describe this experience as an experience of sharing. But even if that is correct, it’s necessary to say exactly why someone who is sharing a smile is in a position to know things about how the other’s emotion is unfolding.
I don’t want to say that interaction only helps if you know that your emotions are locked together. That is, I don’t want to say that someone who is sharing a smile needs to understand the situation in the way I’m describing it. But minimally the fact of reciprocal control must somehow feature in our awareness.
[*The idea in outline: \begin{enumerate} \item the ways our amusements unfold is locked together \item this is in part because a single motor plan has two functions, production of your smile and prediction of my smile \item the single motor process means that we might experience being locked together in some way (not that our emotions are locked together but that our actions are, in something like (but not exactly) we experience actions when seeing ourselves in a mirror or on CCTV (check Johannes’ discussion of this)). \end{enumerate} ]
Here I want to offer a wild conjecture. In joint expressions of emotion there is a single motor plan with two functions, production and prediction. The motor plan both produces your own smile and enables you to predict the way the other’s smile will unfold. [*missing step about monitoring and experience. (The Haggard idea: motor planning can give rise to experiences concerning one's own actions \citep{Haggard:2005sc}.)] Because your plan has this dual function, your experience of the other’s (my?) smile is special. From your point of view, it is almost as if the other is smiling your smile.% \footnote{ Joel caricatured this idea seeing me eating fruit: ‘it’s almost as if I’m eating that fruit.’ } This means that sharing a smile has characteristic phenomenology.
This odd phenomenological effect means that in sharing a smile we can each think of the situation almost as if there were a single smile. And almost as if there were a single state of amusement. (In thinking of the situation like this it is important that we have a subject-neutral conception of the amusement and an agent-neutral conception of the smile.% \footnote{ Tom Smith asked about this. I clarified that I wasn’t suggesting there was a state of amusement which is ours, nor that the subjects are thinking of the situation in this way. That’s the point of the appeal to subject-neutral amusement. It’s a partial model of the situation. } [*Here I think I’m shifting back from the perspective of the participants in sharing a smile to the perspective of the theorist. Probably what I should say is, first, that a theorist can think of the situation in this way and use this to argue, second, that there is a simple, partial conception of the situation that doesn’t require understanding reciprocal control and interlocking emotions but is sufficient for each smiler to have knowledge of the way the other’s emotion unfolds.] So my suggestion is that in sharing a smile you experience my smile almost as if it were yours (or: you experience me almost as if I were smiling your smile), and so you might also experience our situation almost as if it involved a single state of amusement.
It's more like we each plan a single smile.
But---to reply to the objection---these plans have a dual function. Your plan both produces your own smile and enables you to simulate---to experience---my smile. And likewise for my plan. The interdependence of our smilings means that we could each think of the situation as if it were one in which a single state of amusement were responsible for our actions.

conclusion