# Keyboard Shortcuts?

×
• Next step
• Previous step
• Skip this slide
• Previous slide
• mShow slide thumbnails
• nShow notes
• hShow handout latex source
• NShow talk notes latex source

Click here and press the right key for the next slide (or swipe left)

also ...

Press the left key to go backwards (or swipe right)

Press n to toggle whether notes are shown (or add '?notes' to the url before the #)

Press m or double tap to slide thumbnails (menu)

Press ? at any time to show the keyboard shortcuts

\title {Acting Together: Motor Representation and Cooperation \\ Acting Together}

\maketitle

# Motor Representation & Cooperation

\def \ititle {Acting Together}
\def \isubtitle {Motor Representation & Cooperation}
\begin{center}
{\Large
\textbf{\ititle}: \isubtitle
}

\iemail %
\end{center}
In this talk, I will outline a minimal framework for theorising about joint action. I will also argue that attention to the role of motor representation in coordinating joint action proves unexpectedly helpful in enabling us to understand the sophisticated sort of cooperative interactions that are often the focus of philosophical discussions of joint action.

\section{What is Joint Action: The Method of Contrast Cases}

\section{What is Joint Action: The Method of Contrast Cases}
Joint action is a familiar feature of everyday life.
Two sisters cycling to school together are engaged in a joint action,
whereas two strangers who happened to be cycling the same route side-by-side would not be (compare \citealp{gilbert_walking_1990}).
Similarly, when members of a flash mob in the Central Cafe respond to a pre-arranged cue by noisily opening their newspapers, they perform a joint action.
But when someone not part of the mob just happens to noisily open her newspaper in response to the same cue, her action is not part of any joint action.%
\footnote{
See \citet{Searle:1990em}; in his example park visitors simultaneously run to a shelter, in once case as part of dancing together and in another case because of a storm.
Compare \citet{Pears:1971fk} who uses contrast cases to argue that whether something is an ordinary, individual action depends on its antecedents.
}
These and other contrast cases invite the question,
\textbf{What distinguishes joint actions from parallel but individual action?}

This is a valuable question to pursue because joint action raises \textbf{a tangle of scientific and philosophical questions}. % \begin{enumerate} \item Psychologically we want to know which mechanisms make it possible \citep{Sebanz:2006yq,vesper_minimal_2010}. \item Developmentally we want to know when joint action emerges, what it presupposes and whether it might somehow facilitate socio-cognitive, pragmatic or symbolic development \citep{Moll:2007gu,Hughes:2004zj,Brownell:2006gu}. \item Phenomenologically we want to characterise what (if anything) is special about experiences of action and agency when collective agency is involved \citep{Pacherie:2010fk}. \item Metaphysically we want to know what kinds of entities and structures are implied by the existence of joint action \citep{Gilbert:1992rs,Searle:1994lb}. \item And normatively we want to know what kinds of commitments (if any) are entailed by joint action and how these commitments arise \citep{Roth:2004ki}. %, plus a formal account of how practical reasoning for joint action differs (if at all) from individual practical reasoning \citep{Sugden:2000mw,Gold:2007zd} \end{enumerate} % In investigating these questions it is useful to have a conceptual framework which enables us to distinguish systematically between joint and individual action.
This is why we should ask, What distinguishes joint action from parallel but merely individual action?
The first contrast case shows that the difference can’t be just a matter of coordination because people who merely happen to be cycling side-by-side also need to coordinate their actions in order to avoid colliding.
Note also that in both cases each individual's cycling is intentional, so our intentionally cycling together cannot be only a matter of our each intentionally cycling.
The second contrast case shows that the difference can’t just be that the resulting actions have a common effect because merely parallel actions can have common effects too.
At this point it is natural to appeal to intention. If we are performing actions of some type phi, then perhaps for our doing this to be a joint action is just for us to be doing this because we each intend that we, you and I, phi together.
So in the case of the cycling sisters, each would intend that they, the two sisters cycle to school together. I'm going to come back to this idea so it's helpful to give it a label. Let's call it the Simple View.

each sister intends that
they, the sisters, cycle to school together?

Does the appeal to togetherness make this circular? Not as long as we understand 'together' only in the sense in which the three legs of a tripod support the flask \emph{together}.
So we have to understand the intention as concerning an event type that could be a joint action but might also involve merely parallel actions.
\subsection{Simple View}:

Two or more agents perform an intentional joint action exactly 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.

The Simple View intially seems promising because it distinguishes the cases on your left from those on your right ...
So, for instance, the strangers do not intend that they, the two strangers, cycle anywhere, whereas the sisters do plausibly have such an intention.
But we can see that the Simple View is too simple as it stands by adapting an example from Gilbert and Bratman ...
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 being involved in a joint action can't be a matter only of there being something such that we each intend that we do it together.

diagnosis: cooperation

The counterexample shows that you can meet the conditions of the Simple Account without cooperating or being disposed to cooperate. But, arguably, shared agency involves cooperation in some way.

‘The notion of a [shared intention] ... implies the notion of cooperation’

\citep[p.~95]{Searle:1990em}

Searle (1990, p. 95)

If Searle is right, the Simple View must be rejected because you can meet this condition without cooperating or being disposed to cooperate.
Actually a related objection applies to Michael Bratman’s view (or so I argue in \citealp{butterfill:2015_planning}), and it’s possible that the same diagnosis applies: cooperation is missing. Although Bratman isn’t 100% clear about this, his sufficient conditions for shared intention require no more in the way of cooperation than the Simple View does.% \footnote{ Bratman initially \citet[pp.~336--7{Bratman:1992mi} argued that actions can involve shared agency without any of the agents being disposed or committed to support the others; and he takes this to imply that shared agency does not necessarily involve cooperation (see footnote 18, ibid). However, in a more recent discussion Bratman claims (incorrectly, in my view) that, on his view of shared intention, agents’ having a shared intention puts them ‘under rational pres­sure to be willing to some extent to help [each other] if need be’ (\citealp[p.~56]{bratman:2014_book}; see also footnote 38). }
It's just here that we seem to need shared intention ... ... as many philosophers and some scientists have suggested. For example, \citet[p.\ 5]{Gilbert:2006wr}: I take a collective [joint] action to involve a collective [joint] intention.' (There are more examples on your handout.)
\subsection{Shared Intention}
What distinguishes joint actions from parallel but individual actions?
‘the key property of joint action lies in [...] the participants’ having a [...] “shared” intention.’ \citep{alonso_shared_2009} %[pp.\ 444-5]
I take a collective action to involve a collective intention.' \citep[p.\ 5]{Gilbert:2006wr}
The sine qua non of collaborative action is a joint goal [shared intention] and a joint commitment’
\citep[p.\ 181]{tomasello:2008origins}
Shared intentionality is the foundation upon which joint action is built.' \citep[p.\ 381]{Carpenter:2009wq}
it is precisely the meshing and sharing of psychological states \ldots \ that holds the key to understanding how humans have achieved their sophisticated and numerous forms of joint activity'
\citep%[p.\ 369]{Call:2009fk}

?

But what is shared intention? First, it's a technical term: on many accounts, neither shared intentions are shared not intentions. Second, I think everyone will agree that shared intention features alongside ordinary, individual intention in practical reasoning; so that the two are inferrentially integrated. Third, I take it that shared intention is suppose to stand to joint action roughly as ordinary, individual intention stands to ordinary, individual action ...
Beyond this these is much disagreement. Some hold that understanding it requires postulating novel kinds of attitude (\citealp{Searle:1990em}), or novel kinds of subject, namely group \citep{helm_plural_2008} or plural subjects \citep{schmid:2009_plural_bk}, or novel kinds of reasoning \citep{Gold:2007zd}, or novel kinds of commitment (\citealp{Gilbert:1992rs}), or yet further kinds of novelty \citep[e.g.][]{Roth:2004ki,gallotti:2013_social}. The existence of so many fundamentally conflicting approaches underlines the difficulty of understanding shared intention.
I want to suggest that this difficulty motivates re-considering the Simple View. Of course the Simple View is wrong as it stands. But maybe the way to fix it is not to add extra layers of intention or mess with the ontology; maybe reflection on more basic representations and processes involved in acting together will provide a way to understand joint action, one that requires no more intending than is involved in the Simple View.
That, anyway, is what I aim to argue in this talk.
In what follows I will pursue an alternative, minimal strategy for understanding joint action. The key ingredients, in order of appearance, are: multi-agent events, collective goals, and an interagential structure of motor representation.

Three ingredients:

-- multi-agent events

-- collective goals

-- an interagential structure of motor representation

What follows is based on collaborative work with, among others, Cordula Vesper, Natalie Sebanz, Guenther Knoblich and Corrado Sinigaglia. But each of them may disagree with the details of the view I’m presenting here.

## Multi-Agent Events

\section{Multi-Agent Events}

\section{Multi-Agent Events}
I want to start with a claim from Kirk Ludwig's semantic analysis.
A \emph{joint action} is an event with two or more agents, as contrasted with an \emph{individual action} which is an event with a single agent \citep[p.\ 366]{ludwig_collective_2007}.
[Grounding]
Events $D_1$, ...\ $D_n$ \emph{ground} $E$, if: $D_1$, ...\ $D_n$ and $E$ occur;
$D_1$, ...\ $D_n$ are each (perhaps improper) parts of $E$; and
every event that is a proper part of $E$ but does not overlap $D_1$, ...\ $D_n$ is caused by some or all of $D_1$, ...\ $D_n$.
For an individual to be \emph{among the agents of an event} is for there to be actions $a_1$, ...\ $a_n$ which ground this event where the individual is an agent of some (one or more) of these actions.
A joint action is an event with two or more agents.\citep{ludwig_collective_2007}
To see why, consider an example.
Nora and Olive killed Fred. Each fired a shot. Neither shot was individually fatal but together they were deadly. An ambulance arrived on the scene almost at once but Fred didn't make it to the hospital. On the revised simple definition, this event is a joint action just because Nora and Olive are both agents of it. Now suppose that Nora and Olive have no knowledge of each other, nor of each other's actions, and that their efforts are entirely uncoordinated. We might even suppose that Nora and Olive are so antagonistic to each other that they would, if either knew the other's location, turn their guns on each other. The event of their killing Fred is nevertheless a joint action on the revised simple definition.
Why is this a problem?
Because it shows that our present characterisation of joint action as an event with two or more agents doesn't match intutions about contrasts between joint and parallel but merely individual action. So we need to improve on this.

What are we missing?

What is missing from this first attempt at characterising joint action? I think one missing feature is the notion of a collective goal. Here I need to go slowly ...

## Collective Goals

\section{Collective Goals}

\section{Collective Goals}
Ayesha takes a glass and holds it up while Beatrice pours prosecco; unfortunately the prosecco misses the glass and soak Zachs’s trousers.
Here are two sentences, both true:

The tiny drops fell from the bottle.

- distributive

The tiny drops soaked Zach’s trousers.

- collective

The first sentence is naturally read *distributively*; that is, as specifying something that each drop did individually. Perhaps first drop one fell, then another fell.
But the second sentence is naturally read *collectively*. No one drop soaked Zach’s trousers; rather the soaking was something that the drops accomplised together.
If the sentence is true on this reading, the tiny drops' soaking Zach’s trousers is not a matter of each drop soaking Zach’s trousers.
Now consider an example involving actions and their outcomes:

Their thoughtless actions soaked Zach’s trousers. [causal]

- ambiguous

This sentence can be read in two ways, distributively or collectively. We can imagine that we are talking about a sequence of actions done over a period of time, each of which soaked Zach’s trousers. In this case the outcome, soaking Zach’s trousers, is an outcome of each action.
Alternatively we can imagine several actions which have this outcome collectively---as in our illustration where Ayesha holds a glass while Beatrice pours. In this case the outcome, soaking Zach’s trousers, is not necessarily an outcome of any of the individual actions but it is an outcome of all of them taken together. That is, it is a collective outcome.
(Here I'm ignoring complications associated with the possibility that some of the actions collectively soaked Zach’s trousers while others did so distributively.)
Note that there is a genuine ambiguity here. To see this, ask yourself how many times Zach’s trousers were soaked. On the distributive reading they were soaked at least as many times as there are actions. On the collective reading they were not necessarily soaked more than once. (On the distributive reading there are several outcomes of the same type and each action has a different token outcome of this type; on the collective reading there is a single token outcome which is the outcome of two or more actions.)
Conclusion so far: two or more actions involving multiple agents can have outcomes distributively or collectively. This is not just a matter of words; there is a difference in the relation between the actions and the outcome.
Now consider one last sentence:

The goal of their actions was to fill Zach’s glass. [teleological]

Whereas the previous sentence was causal, and so concened an actual outcome of some actions, this sentence is teleological, and so concerns an outcome to which actions are directed.

- also ambiguous

Like the previous sentence, this sentence has both distributive and collective readings. On the distributive reading, each of their actions was directed to an outcome, namely soaking Zach’s trousers. So there were as many attempts on his trousers as there are actions. On the collective reading, by contrast, it is not necessary that any of the actions considered individually was directed to this outcome; rather the actions were collectively directed to this outcome.
Conclusion so far: two or more actions involving multiple agents can be collectively directed to an outcome.
Where two or more actions are collectively directed to an outcome, we will say that this outcome is a *collective goal* of the actions. Note two things. First, this definition involves no assumptions about the intentions or other mental states of the agents. Relatedly, it is the actions rather than the agents which have a collective goal. Second, a collective goal is just an actual or possible outcome of an action.
An outcome is a \emph{collective goal} of two or more actions involving multiple agents if it is an outcome to which those actions are collectively directed.
We can extend our defintion of joint to include the notion of a collective goal ...

Joint action:

An event with two or more agents.

An event with two or more agents where the actions have a collective goal.

Is this good enough? I think it isn’t ...
For example, when two agents between them lift a heavy block by means of each agent pulling on either end of a rope connected to the block via a system of pulleys, their pullings count as coordinated just because the rope relates the force each exerts on the block to the force exerted by the other.
In this case, the agents' activities are coordinated by a mechanism in their environment, the rope, and not necessarily by any psychological mechanism.
To make a conjecture based on work with bees and ants, in some cases ...
the coordination needed for a collective goal may even be supplied by behavioural patterns \citep{seeley2010honeybee} and pheromonal signals \citep[pp.\ 178-83, 206-21]{hoelldobler2009superorganism}.
So the definition seems inadequate. Either it includes things that are not joint actions at all, or else it captures a notion of joint action that is broader than the core cases of shared agency that have been of primary interest to philosophers.
This is not to say that collective goals never involve psychological states.
In fact, one way for several actions to have a collective goal is for their agents to be acting on a shared intention;
a shared intention supplies the required coordination.
We’ve been considering the idea that we can extend our defintion of joint to include the notion of a collective goal ... On our current working definition, a joint action is an event with two or more agents where the actions have a collective goal.

The defintion is still too broad. To make progress we need to think not just about collective goals but about the different kinds of thing in virtue of which some actions can have a collective goal ...

## Collective Goals and Motor Representations

\section{Collective Goals and Motor Representations}

\section{Collective Goals and Motor Representations}

In virtue of what do actions involving multiple agents ever have collective goals?

Recall how Ayesha takes a glass and holds it up while Beatrice pours prosecco; and unfortunately the prosecco misses the glass, soaking Zachs’s trousers. Ayesha might say, truthfully, ‘The collective goal of our actions was not to soak Zach's trousers in sparkling wine but only to fill this glass.’ What could make Ayesha’s statement true?
As this illustrates, some actions involving multiple agents are purposive in the sense that
among all their actual and possible consequences,
there are outcomes to which they are directed
and the actions are collectively directed to this outcome
so it is not just a matter of each individual action being directed to this outcome.
In such cases we can say that the actions have a collective goal.
As what Ayesha and Beatrice are doing---filling a glass together---is a paradigm case of joint action, it might seem natural to answer the question by invoking a notion of shared (or collective') intention. Suppose Ayesha and Beatrice have a shared intention that they fill the glass. Then, on many accounts of shared intention,
the shared intention involves each of them intending that they, Ayesha and Beatrice, fill the glass; or each of them being in some other state which picks out this outcome.
The shared intention also provides for the coordination of their actions (so that, for example, Beatrice doesn't start pouring until Ayesha is holding the glass under the bottle). And coordination of this type would normally facilitate occurrences of the type of outcome intended. In this way, invoking a notion of shared intention provides one answer to our question about what it is for some actions to be collectively directed to an outcome.
Are there also ways of answering the question which involve psychological structures other than shared intention? In this paper we shall draw on recent discoveries about how multiple agents coordinate their actions to argue that the collective directedness of some actions to an outcome can be explained in terms of a particular interagential structure of motor representations. Our actions having collective goals is not always only a matter of what we intend: sometimes it constitutively involves motor representation.

one agent

Let me start by stepping back and consider an individual action. Consider what Ayesha and Beatrice do---their attempt to fill Zach's glass by one pouring prosecco while the other holds a glass---but now imagine that one person does both parts of the action.
In virtue of what do actions involving just one agent ever have goals?
A standard answer involves appeal to intention. For an intention identifies an outcome, coordinates some of the agent’s actions around that outcome, and coordinates them in such a way that, normally, the coordination would facilitate the occurrence of the outcome. Thus someone's intention to wash the dishes might, for example, constrain the order of her actions so that that the prosecco glasses are done before greasy pans. In this way, appealing to an intention concerning an outcome and its role in coordinating actions can sometimes allow us to explain in virtue of what several actions are collectively directed to that outcome. Are there other facts in virtue of which multiple actions involving just one agent can be collectively directed to an outcome?
But some philosophers have argued that some actions have goals in virtue of motor representation rather than intention. It will be helpful to outline these arguments since my aim today is an attempt to generalise such arguments from one agent to multiple agents.

motor representations

can

represent outcomes

Let us start by reviewing some almost uncontroversial facts about the coordinating role of motor representations for two or more actions involving just one agent. Some motor representations represent outcomes to which actions could be directed, outcomes such as the grasping of a glass or the pressing of a switch rather than mere bodily configurations and joint displacements \citep{hamilton:2008_action, cattaneo:2009_representation}.

and

trigger planning-like processes

Relatedly, motor representations can trigger processes which are like planning in some respects. These processes are planning-like in that they involve starting with representations of relatively distal outcomes and gradually filling in details, resulting in motor representations that can be hierarchically arranged by the means-end relation \citep{bekkering:2000_imitation,grafton:2007_evidence}. Some processes triggered by motor representations are also planning-like in that they involve meeting constraints on the selection of means by which to bring about one outcome that arise from the need to select means by which, later, to bring about another outcome \citep{jeannerod_motor_2006, zhang:2007_planning, rosenbaum:2012_cognition}.
Consider this case. An agent fills a glass by holding it in one hand, holding the bottle in the other, bringing the two together and pouring from the bottle into the glass.
[*demonstrate].
It’s a familiar idea that motor representations of outcomes resemble intentions in that they can trigger processes which are like planning in some respects. These processes are like planning in that they involve starting with representations of relatively distal outcomes and gradually filling in details, resulting in a structure of motor representations that can be hierarchically arranged by the means-end relation \citep{bekkering:2000_imitation, grafton:2007_evidence}. Processes triggered by motor representations of outcomes are also planning-like in that they involve selecting means for actions to be performed now in ways that anticipate future actions \citep{jeannerod_motor_2006,zhang:2007_planning,rosenbaum:2012_cognition}.
Now in this action of moving a mug, there is a need, even for the single agent, to coordinate the exchange between her two hands. (If her action is fluid, she may proactively adjust her left hand in advance of the mug’s being lifted by her right hand \citep[compare][]{diedrichsen:2003_anticipatory,hugon:1982_anticipatory, lum:1992_feedforward}.) How could such tight coordination be achieved? Part of the answer involves the fact that motor representations and processes concerning the actions involving each hand are not entirely independent of each other. Rather there is a plan-like structure of motor representation for the whole action and motor representations concerning actions involving each hand are components of this larger plan-like structure. It is in part because they are components of a larger plan-like structure that the movements of one hand constrain and are constrained by the movements of the other hand.
But how is any of this relevant to our question about in virtue of what an individuals’ actions can have a goal?
The idea is that motor representations can ground the directedness of actions to goals, much as intentions can. For, like intentions, motor representations represent outcomes, trigger planning-like processes which compute means-ends relations, and thereby provide for the coordination of actions.

Conjecture

Sometimes, when two or more actions involving multiple agents are, or need to be, coordinated:

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.
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 concern 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 for this conjecture, 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)

Kourtis et al (2014, figure 1b)

Here's the procedure.

joint

individual-bimanual

individual-unimanual

This is fine but what are we going to measure?

Kourtis et al (2014, figure 1c)

CNV

This is a signal of motor preparation for action which is time-locked to action onset. In previous research, Kourtis et al show (i) that the CNV occurs when joint action partners act, suggesting that when acting together we represent others' actions motorically as well as our own \cite{kourtis:2012_predictive}; and (ii) (roughly) a stronger CNV occurs in relation to actions of others one is engaged in joint action than in relation to actions of others one is merely observing \cite{kourtis:2010_favoritism}.
Kourtis et al hypothesised that in actions like clinking glasses, A single outcome represented is motorically, which triggers planning-like processes concerning all the agents' actions. This leads to the prediction that the CNV in joint action will resemble that occurring in bimanual action more than that occuring in unimanual action.

Kourtis et al (2014, figure 4a)

... and this is exactly what they found.

Conjecture

Sometimes when two or more actions involving multiple agents are, or need to be, coordinated:

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.
There is more evidence for this conjecture than I have given here, but there is not a lot more converging evidence. This is a conjecture that we hope will be tested further rather than something we take to be established already.

prediction

Need to emphasise that this conjecture is a source of predictions. Here's one.

Conjecture

Sometimes when two or more actions involving multiple agents are, or need to be, coordinated:

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 about coordination? There is a little bit of direct evidence for this that I won't mention. But I do want to take you through why the interagential structure of motor representation might in theory result in the agents actions being coordinated.
Earlier we considered what is involved in performing an ordinary, individual action, where an agent fills a glass from a bottle, taking one in each hand and moving them in a carefully coordinated way. Compare this individual action with the same action performed by two agents as a joint action. One agent takes the glass while the other takes the bottle. The joint action is like the individual action in several respects.
First, the goal to which the joint action is directed is the same, namely to move the mug from here to there.
Second, there is a similar coordination problem---the agents’ two hands have to meet.
And, third, the evidence we have mentioned suggests that in joint action, motor representations and processes occur in each agent much like those that would occur if this agent were performing the whole action alone.

Suppose the agents' planning-like motor processes are similar enough that, in this context, they will reliably produce approximately the same plan-like structures of motor representations.
Then having a single planning-like motor process for the whole joint action in each agent means that
\begin{enumerate}
\item in each agent there is a plan-like structure of motor representations concerning each of the others’ actions,
\item each agent's plan-like structure concerning another's actions is approximately the same as any other agent's plan-like structure concerning those actions,
\item each agent's plan-like structure concerning her own actions is constrained by her plan-like structures concerning the other’s actions.
\end{enumerate}
So each agent’s plan-like structure of motor representations concerning her own actions is indirectly constrained by the other agents' plan-like structures concerning their own actions
by virtue of being directly constrained by her plan-like structures concerning their actions.
In this way it is possible to use ordinary planning-like motor processes to achieve coordination in joint action.
What enables the two or more agents' plan-like structures of motor representations to mesh is not that they represent each other's plans but that they processes motorically each other's actions and their own as parts of a single action.

So how does the joint action differ from the corresponding individual action?
There are at least two differences.
First, we now have two plan-like structures of motor representations because in each agent there is a planning-like motor process concerning the whole action.
These two structures of motor representations have to be identical or similar enough that the differences don’t matter for the coordination of the agents’ actions---let us abbreviate this by saying that they have to \emph{match}.
The need for matching planning-like structures is not specific to joint action;
it is also required where one agent observing another is able to predict her actions thanks to planning-like motor processes concerning the other’s actions (we mentioned evidence that this occurs above).
A second difference between the joint action and the individual action is this.
In joint action there are planning-like motor processes in each agent concerning some actions which she will not eventually perform.
There must therefore be something that prevents part but not all of the planning-like motor process leading all the way to action.
Exactly how this selective prevention works is an open question.
We expect bodily and environmental constraints are often relevant.
There may also be differences in how others’ actions are processed motorically \citep[compare][]{novembre:2012_distinguishing}.
\footnote{\citep[p.\ 2901]{novembre:2012_distinguishing}: 'in the context of a joint action—the motor control system is particularly sensitive to the identity of the agent (self or other) of a represented action and that (social) contextual information is one means for achieving this distinction'}
And inhibition could be involved too \citep[compare][]{sebanz:2006_twin_peaks}.
My proposal, then, is this. In both practical reasoning and motorically, sometimes agents are able to achieve coordination for joint action not by representing each others’ plans but by treating each other's actions and their own as if they were parts of a single action.
So perhaps joint action is not always only a matter of intention, knowledge or commitment: perhaps sometimes joint action constitutively involves motor representation.

collective goals

So far this has all been about coordination. But our question was about collective goals.
Suppose Ayesha and Beatrice have a shared intention that they fill the glass. Then, on many accounts of shared intention,
the shared intention involves each of them intending that they, Ayesha and Beatrice, fill the glass; or each of them being in some other state which picks out this outcome.
The shared intention also provides for the coordination of their actions (so that, for example, Beatrice doesn't start pouring until Ayesha is holding the glass under the bottle). And coordination of this type would normally facilitate occurrences of the type of outcome intended. In this way, invoking a notion of shared intention provides one answer to our question about what it is for some actions to be collectively directed to an outcome.
What we've just seen is that a parallel answer can be given by appeal to i.a.s.m.r. ...

Joint action:

An event with two or more agents.

We’ve been considering the idea that we can extend our defintion of joint to include the notion of a collective goal ...

An event with two or more agents where the actions have a collective goal.

An event with two or more agents where the actions have a collective goal in virtue of an interagential structure of motor representations.

## Motor Representation Underpins Cooperation

\section{Motor Representation Underpins Cooperation}

\section{Motor Representation Underpins Cooperation}
Recall our issue earlier with the Simple View

diagnosis: cooperation

The counterexample shows that you can meet the conditions of the Simple Account without cooperating or being disposed to cooperate. But, arguably, shared agency involves cooperation in some way.

‘The notion of a [shared intention] ... implies the notion of cooperation’

\citep[p.~95]{Searle:1990em}

Searle (1990, p. 95)

Where our actions have a collective goal in virtue of an interagential structure of motor representations, we are not merely acting together: we are acting as one.

Why is this true? Because in the sort of parallel-planning triggered by the motor representations in an interagential structure of motor representations, there is no distinction between actions I will perform and actions you will perform.
I am, in effect, just trying to work out the best way to achieve the outcome irrespective of who does what; and so are you; and this is the hallmark of effective cooperation.

the Simple View revised

Let's go back to the Simple View ...

Two or more agents perform an intentional joint action exactly 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 to be careful in specifying under what description they intend that they phi. To avoid circularity can't always be the case that phi is an intentional joint action. Bratman says it is cooperatively neutral. This is weak. Maybe we can say:

φ comprises two or more actions involving multiple agents where the actions have a collective goal in virtue of an interagential structure of motor representation.

I think this gets around the Tarrantino walkers counterexample. (Because if you have the iasmr you don't need a gun!)
But it leaves us with another problem ...
People can't intend phi under this description unless they can identify the interagential structure of motor representation we have been characterising.
So we have to give up on this idea as it stands. But maybe we can modify it.

interagential structure of motor representation grounds collective goal

> experience of act type

> concept of act type

φ is an act-type we know through experiences arising from interagential structure of motor representations grounding collective goals.

Compare individual action. We know what it is to grasp by virtue of experiences created by motor representations. ...

conclusion

In conclusion, my question was about in virtue of what ... collective goals. Many researchers have answered this question by appeal to one or another kind of shared intention. What we have shown is that in some cases the right answer to the question involves motor representation rather than intention. And, more tenatively, this suggests that there may be a role for motor representation in characterising joint action. Perhaps understanding joint action and shared intention requires appeal not just to intention, commitment and the rest, but also to motor representation.