\title {Acting Together: Motor Representation and Cooperation \\ Acting Together}
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\def \ititle {Acting Together}
\def \isubtitle {Motor Representation & Cooperation}
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\textbf{\ititle}: \isubtitle
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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?}
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.
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 to their actions.
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.
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
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}
This definition is too broad.
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.
Collective Goals
\section{Collective Goals}
\section{Collective Goals}
Let me first explain something about this notion of a collective goal ...
Ayesha takes a glass and holds it up while Beatrice pours prosecco;
unfortunately the prosecco misses the glass and soak Zachs’s trousers.
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 ...
Collective Goals and Motor Representations
\section{Collective Goals and Motor Representations}
\section{Collective Goals and Motor Representations}
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?
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.
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)
Kourtis et al (2014, figure 4a)
... and this is exactly what they found.
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.
Why would this be helpful?
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}.
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. ...
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)
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 to their actions.