--------
The challenge is to explain the emergence, in evolution or development, of sophisticated
forms of human activity including, referential communication and mindreading.
A number of researchers have suggested that meeting this challenge requires us to invoke
some kind of social interaction ...
--------
According to what Moll and Tomasello call the Vygotskian Intelligence Hypothesis,
‘participation in cooperative ... interactions … leads children to construct uniquely powerful forms of cognitive representation.’
\citep{Moll:2007gu}
--------
‘perception, action, and cognition are grounded in social interaction’
\citep[p.\ 103]{Knoblich:2006bn}
--------
‘human cognitive abilities … [are] built upon social interaction’
\citep{sinigaglia:2008_roots}
I'm going to assume that they are right.
--------
If we take these ideas seriously, the first question we need to ask is, What kinds of social interaction matters for the emergence of sophisticated human activities?
--------
There seems to be some consensus on the idea that joint action is particularly important.
--------
So the challenge was to explain the emergence of sophisticated human activities including referential communication and mindreading.
--------
The conjecture I want to consider, borrowed from a variety of researchers, is that
joint action plays a role in explaining how sophisticated human activities emerge.
There is a compelling objection to this conjecture.
It will take me a while to explain what the objection is.
The objection arises when we ask ask what joint action is.
--------
--------
Minimally, an account of joint action should explain
what distingiushes joint action from parallel but merely individual action.
--------
A paradigm case of joint action would be two sisters cycling to school together.
--------
By contrast, two strangers cycling side-by-side are performing parallel but merely individual actions.
--------
Or, to take another paradigm case,
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.
}
--------
Lots of philosophers and some psychologists think that all joint actions involve
shared intention, and even that characterising joint action is fundamentally a matter
of characterising shared intention.
‘I take a collective action to involve a collective [shared] 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}
--------
‘the key property of joint action lies in its internal component [...] in the participants’ having
a “collective” or “shared” intention.’
\citep[pp.~444--5]{alonso_shared_2009}
--------
‘Shared intentionality is the foundation upon which joint action is built.’
\citep[p.~381]{carpenter:2009_howjoint}
--------
It is helpful to draw a parallel with individual action ...
Consider Davidson’s question is, Which events are actions?
Suppose we ask, Which events are actions?
(This is Davidson’s question.)
Here the contrast is with things that merely happen to an agent.
To illustrate, we might be struck by the contrast between your arm being caused to go
up by forces beyond your control, and the action you perform when you raise your arm.
Or we might be struck by the contrast between mere reflexes, such as the eyeblink reflex,
and the action of blinking your eyes (perhaps to greet someone).
--------
One quite natural and certainly influential way to answer this question is by
appeal to intention. The idea is that events are actions in virtue of being
appropriately related to an intention of yours.
Note that I’m not confidently endorsing this answer; in fact I’m not even
confident that the question is ultimately the right question to ask.
I’m just suggesting this is a reasonably straightforward starting point for us.
--------
This question about ordinary, individual action is parallel to our current working
question about joint action, which we might phrase as ‘Which events are *joint* actions’ ...
--------
Now we can see one attraction of appealing to shared intention.
It allows us to give a parallel answer to the question about joint action:
a joint action is an event which is appropriately related to a shared intention.
So to the extent that we are persuaded by the standard account of which events are actions,
it is natural to aim for a structurally parallel account of which events are joint actions.
To do this we merely have to characterise shared intentions.
As we shall see, there are long running, deep conflicts over the nature of shared
intention. The range of different approaches can be quite daunting.
This parallel between intention and shared intention is important because it is
a rare point on wihch almost everyone will agree.
\textbf{Despite the disagreement on details, I think one thing almost everyone agrees about
is this: shared intention is to joint action at least approximately what
ordinary individual intention is to ordinary, individual action.}
--------
It’s important to acknowledge that we haven’t yet said anything very informative
about what shared intention is.
The question was, Which events are joint actions?
The answer was, those which stand in an appropriate relation to a shared intention.
Then we ask what a shared intention is.
And the answer is, it’s something in virtue of which events are joint actions.
I don’t think the circle makes this completely useless;
but I’m mentioning the circularity to stress that we don’t yet have an account
of what shared intention is.
An account of shared intention should to provide deep insight
into the nature of shared agency.
--------
‘I will … adopt Bratman’s … influential formulation of joint action …
each partner needs to
intend to perform the joint action together ‘‘in accordance with and because of
meshing subplans’’ (p. 338) and this needs to be common knowledge between the participants.’
\citep[][p.\ 281]{carpenter:2009_howjoint}
--------
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.
--------
--------
Note that the conditions require not just that we intend the joint action, but that we
intend it because of each other's intentions, where this is common knowledge.
--------
So we need not just intentions about intentions ...
--------
... also you need to know things about my knowledge of your intentions concerning my intentions.
--------
This indicates that, in general, having shared intentions requires mindreading at close to (or perhaps just beyond) the limits of most adult humans' abilities.
Bratman's account of shared intention is an example where
reciprocity is modeled as higher-order escalation.
Objection: Meeting the sufficient conditions for joint action given by
Bratman’s account could not significantly \textit{explain} the development
of an understanding of minds because it already \textit{presupposes} too
much sophistication in the use of psychological concepts.
And this is a problem for us ...
--------
This is a problem because our conjecture was that joint action plays a role in explaining how sophisticated human activities emerge.
--------
But if joint action presupposes mindreading at close to the limits of human abilities,
and if mindreading abilities are a paradigm case of humans' cognitive sophistication,
then we must reject the conjecture.
For in appealing to joint action we would be presupposing what was supposed to be explained.
In what follows I want to defend the conjecture by identifying a way around the objection.
But before I do this, I want to mention a problem with the objection ...
--------
Note that these conditions are offered as sufficient but not necessary.
(Bratman originally claimed that they were necessary and sufficient, but
nothing in the construction rules out alternative realisations of the functional
characterisation of shared intention.)
As it stands, then, this objection does not establish much. It concerns conditions
imposed by the substantial account of shared intention which are sufficient but not
necessary conditions.
The substantial account is supposed to characterise one—perhaps one among many—ways
in which the functional role of shared intentions can be realised. So the objection
serves only to raise a question.
\textbf{Are there in fact alternative sufficient conditions
for shared intention, conditions that can be met without already having abilities to use
psychological concepts whose development was supposed to be explained by joint action?}
--------
The answer to this question is not entirely straightforward. We must begin with the
functional roles of shared intention, for these provide necessary conditions. One of
the roles of shared intentions is to coordinate planning. What does coordinating planning
involve? Intuitively the idea is that just as individual intentions serve to coordinate an
individual’s planning over time, so shared intentions coordinate planning between agents.
(I use the terms ‘individual intention’ and ‘individual goal’ to refer to intentions and
goals explanatory of individual actions; an ‘individual action’ is an action performed by
just one agent such as that described by the sentence ‘Ayesha repaired the puncture all
by herself’.) A second role for shared intentions is to structure bargaining concerning
plans. To understand these roles it is essential to understand what ‘planning’ means in
this context. The term ‘planning’ is sometimes used quite broadly to encompass processes
involved in low-level control over the execution of sequences of movements, as is often
required for manipulating objects manually \citep[e.g.][]{en_1535}, as well as processes
controlling the movements of a limb on a single trajectory \citep[e.g.][]{en_1681}. In Bratman’s account and this paper, the term ‘planning’ is used in a narrower sense. Planning in this narrow sense exists to coordinate an agent’s various activities over relatively long intervals of time; it involves practical reasoning and forming intentions which may themselves require further planning, generating a hierachy of plans and subplans. Paradigm cases include planning a birthday party or planning to move house.
Given the functional roles of shared intention, when (if ever) must the states which realise shared intentions include intentions about others’ intentions? Coordinating plans with others does not seem always or in principle to require specific intentions about others’ intentions. It is plausible that in everyday life some of our plans are coordinated largely thanks to a background of shared preferences, habits and conventions. Consider, for example, people who often meet in a set place at a fixed time of day to discuss research over lunch. These people can coordinate their lunch plans merely by setting a date and following established routine; providing nothing unexpected happens, they seem not to need intentions about each other’s intentions. Within limits, then, coordinating plans may not always require intentions about intentions. The same may hold for structuring bargaining. But when the background of shared preferences, habits and conventions is not sufficient to ensure that our plans will be coordinated, it is necessary to monitor or manipulate others’ plans. And since intentions are the basic elements of plans (in the special sense of ‘plan’ in terms of which Bratman defined shared intention), this means monitoring or manipulating others’ intentions. The background which makes for effortlessly coordinated planning is absent when our aims are sufficiently novel, when the circumstances sufficiently unusual (as in many emergencies), and when our co-actors are sufficiently unfamiliar. In all of these cases, coordinating plans and structuring bargaining will involve monitoring or manipulating others’ intentions. Now this does not necessarily involve forming intentions about their intentions because, in principle, monitoring and manipulating others’ intentions could (within limits) be achieved by representing states which serve as proxies for intentions rather than by representing intentions as such, much as one can (within limits) monitor and manipulate others’ visual perceptions by representing their lines of sight. But possession of general abilities to monitor and manipulate others’ intentions does require being able to form intentions about others’ intentions.
The question was whether there are sufficient conditions for shared intention which do not presuppose abilities to use psychological concepts whose development is supposed to be explained by joint action. As promised, the answer is not straightforward. In a limited range of cases, coordinating plans and perhaps structuring bargaining does not appear to require insights into other minds. But in other cases, particularly cases involving novel aims or agents unfamiliar with each other, intentions about others’ intentions are generally required.
The main question for this section was whether Bratman’s account captures a notion of joint action suitable for explaining the early development of children’s abilities to think about minds. Some of the joint actions which young children engage in involve novel aims, and some involve unfamiliar partners. So if these joint actions did involve coordinating planning and structuring bargaining, they could not rest on a shared background but would require abilities to form intentions about others’ intentions. It follows that joint action would presuppose much of the sophistication in the use of psychological concepts whose development it was supposed to explain. So given the premise that joint action plays a role in explaining early developments in understanding minds, it cannot be the case that the joint actions children engage in as soon as they engage in any joint actions involve shared intentions as characterised by Bratman.
--------
How to get around the objection?
--------
The objection arises because not all of the following claims are true:
%
\begin{quote}
(1) joint action fosters an understanding of minds;
(2) all joint action involves shared intention; and
(3) a function of shared intention is to coordinate two or more agents’ plans.
\end{quote}
%
These claims are inconsistent because if the second and third were both true, abilities to engage in joint action would presuppose, and so could not significantly foster, an understanding of minds.
What are our options?
--------
This is a bad option; it either involves rejecting claims about intention that
amount to saying there is no such thing as intention, or else it involves breaking the
parallel between intention and shared intention.
But that parallel is pretty much all we have to anchor or understanding of shared intention.
--------
This is the claim I will eventually reject. But first let us examine children’s capacities.
--------
--------
Objection: ‘Despite the common impression that joint action needs to be dumbed down
for infants due to their ‘‘lack of a robust theory of mind’’
... all the important social-cognitive building
blocks for joint action appear to be in place:
1-year-old infants
understand quite a bit about others’ goals and intentions and what
knowledge they share with others’
\citep[p.~383]{carpenter:2009_howjoint}.
Carpenter conflates goals and intentions, so ignores the key difference
between actions and plans.
--------
‘I ... adopt Bratman’s (1992) influential formulation of joint
action or shared cooperative activity.
Bratman argued that in order for
an activity to be considered shared or joint each partner needs to intend
to perform the joint action together ‘‘in accordance with and because of
meshing subplans’’ (p. 338) and this needs to be common knowledge between
the participants’
\citep[p.~381]{carpenter:2009_howjoint}.
So: the objection I just offered to taking Bratman’s account of shared intention
and joint action to characterise the notion of joint action of interest in explaining
development was narrowly theoretical.
The objection was that you can’t explain the developmental emergence of mindreading by invoking joint action
if your account of joint action implies that abilities to perform joint actions
presuppose sophisticated mindreading.
Accepting this theoretical objection would be consistent with accepting
Carpenter’s claim. The only consequence is that we would have to reject the
conjecture that you can explain the developmental emergence of mindreading
by invoking joint action.
--------
So I think Carpenter is saying: the objection is correct, and we should reject
the conjecture.
--------
Task: give the tool to another person, who needs to put the spherical end
into the box. (Tip: you need to grasp it by the spherical end and pass it
so that the other takes the cube-end; they can then insert it optimally.)
--------
‘3- and 5-year-old children do not consider another person’s actions in
their own action planning (while showing action planning when acting
alone on the apparatus).
--------
Seven-year-old children and adults
however, demonstrated evidence for joint action planning. ... While adult participants
demonstrated the presence of joint action planning from the very
first trials onward, this was not the case for the 7-year-old
children who improved their performance across trials.’
\citep[p.~1059]{paulus:2016_development}
--------
‘One child had to insert the turn-tool on the right of the apparatus and
then turn so that the metal rod stretching across moved the panel out of
the way of the ball. The other person could then insert the push tool on
the left, pushing the silver ball into the hole similar to a billiard cue.’
\citep{warneken:2014_young}
--------
Unidirectional : child A has to select the tool that B doesn’t have.
Bidirectional : child A can select either tool.
‘(a) Unidirectional: The left box will be opened first. Only the left
child has a choice. For success, this child has to choose the push tool
(lower left: thick handle, long thin top). The partner child has to
retrieve the only available turn tool (upper right: thick handle, short
thin top).’
\citep{warneken:2014_young}
--------
BU - first bidirectional then unidirectional.
The three year olds are hopeless in all conditions except the bidirectional
condition when they have first had the unimanual condition.
So there is no forward planning, but there is some evidence that three-year-olds
can take into account what another has done.
‘by age 3 children are able to learn, under certain circumstances, to take
account of what a partner is doing in a collaborative problem-solving
context. By age 5 they are already quite skillful at attending to and even
anticipating a partner’s actions’ \citep[p.~57]{warneken:2014_young}.
--------
Note that the conditions require not just that we intend the joint action, but that we
intend it because of each other's intentions, where this is common knowledge.
--------
All the evidence has suggests that there is a mismatch between
Bratman’s account of joint action
and
1- to 3-year-olds’ joint action abilities.
Let’s consider two more studies on this ...
--------
I started with Carpenter’s objection ...
Objection: ‘Despite the common impression that joint action needs to be dumbed down
for infants due to their ‘‘lack of a robust theory of mind’’
... all the important social-cognitive building
blocks for joint action appear to be in place:
1-year-old infants
understand quite a bit about others’ goals and intentions and what
knowledge they share with others’
Carpenter conflates goals and intentions, so ignores the key difference
between actions and plans.
‘I ... adopt Bratman’s (1992) influential formulation of joint
action or shared cooperative activity.
Bratman argued that in order for
an activity to be considered shared or joint each partner needs to intend
to perform the joint action together ‘‘in accordance with and because of
meshing subplans’’ (p. 338) and this needs to be common knowledge between
the participants’
It turns out, I think, that Carpenter is wrong to this extent.
Whatever exactly one-year-olds mindreading abilities, they do not seem
to be making much use of information about others’ intentions in performing
joint actions. And so it is wrong to think of their abilities in terms of
Bratman’s account of joint actions.
--------
So with respect to our overall line of enquiry,
it may still be possible to hold on to the conjecture if we can
overcome the objection.
--------
--------
Methods: still face; replay (infants detect whether caregiver reacts, so are
less satisifed with a replay).
\citet[p.~196]{brownell:2011_early} comment: ‘infants become progressively
tuned to the timing and structure of dyadic exchange’
--------
\citet[p.~197]{brownell:2011_early} comment:
‘adult-infant dyadic interactions expand to include objects, events, and
individuals outside of the dyad (Moore and Dunham 1995)’
--------
\citet[p.~197]{brownell:2011_early} comment:
‘Eventually, infants begin themselves to initiate joint action with
adults and to respond in unique ways when adults violate their
expectations for participation in the joint activity. For example, if a
parent becomes distracted during peek-a-boo and fails to take her turn,
12-month olds may try to re-start the game by vocalizing to the adult or
by re- enacting a well-rehearsed part of the game such as placing the
cloth over their own face and waiting. One-year olds also begin to point
to interesting sights and events to share their interest and affect and
they expect adults to respond appropriately by looking (Liszkowski, et al
2006).’
‘infants learn about cooperation by participating in joint action
structured by skilled and knowledgeable interactive partners before they
can represent, understand, or generate it themselves. Cooperative joint
action develops in the context of dyadic interaction with adults in which
the adult initially takes responsibility for and actively structures the
joint activity and the infant progressively comes to master the
structure, timing, and communications involved in the joint action with
the support and guidance of the adult. ... Eager participants from the
beginning, it takes approximately 2 years for infants to become
autonomous contributors to sustained, goal-directed joint activity as
active, collaborative partners’
\citep[p.~200]{brownell:2011_early}.
‘Without the structure and scaffolding provided by the expert adult
partner, 1-year-old children are unable to generate and sustain joint
action with each other in the service of an external goal. By age two,
however, they can do so readily, even with unfamiliar agemates and on
novel, unfamiliar tasks’
\citep[p.~204]{brownell:2011_early}.
--------
Ages: 14, 18 and 24 months.
Elevator task: free an object from a cylinder.
Two roles. Role A: position yourself in the right
location to retrieve the target object. Role B: push up the cylinder
and hold it in place while another retrieves it.
--------
‘The 14-month-olds of this study displayed coordinated behaviors in the
elevator task Role A of positioning themselves in the right location and
retrieving the target object from the cylinder when the partner pushed it
up, but they had major problems performing Role B, pushing the cylinder up
and holding it in place until the partner could fetch the object. If they
pushed up the cylinder at all, they would repeatedly drop it when the other
person was just about to take the object out’ \citep{warneken:2007_helping}.
\citet[p.~200]{brownell:2011_early} comment:
‘Across these non-routine tasks, 18-month olds’ behavior with the adult
partner was rated as predominantly “uncoordinated” (vs. “coordinated” or
“very coordinated”) and the children exhibited “low” cooperative engagement
(vs. “medium” or “high”). On those tasks requiring children to anticipate
the partner’s actions and to adjust their behavior accordingly, 18-month
olds’ performance did not differ from chance. By age two, children operated
at “medium” levels of cooperative engagement and were above chance in
anticipating and coordinating their behavior with the adult.’
‘social coordinations show a marked improvement between children at 14 and
18 months of age’ \citep{warneken:2007_helping}.
--------
--------
How to get around the objection?
Maybe we have to construct an alternative notion of joint action?
--------
‘all sorts of joint activity is possible without conscious goal
representations, complex reasoning, and advanced self-other understanding ...
both in other species and in our own
joint behavior as adults, some of which occurs outside of reflective
awareness ...
In studying
its development in children the problem is how to characterize and
differentiate primitive, lower levels of joint action operationally from more
complex and cognitively sophisticated forms’
\citep[p.~195]{brownell:2011_early}.
--------
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.
--------
Here are two sentences, both true:
The tiny drops fell from the bottle.
The tiny drops soaked Zach’s trousers.
--------
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]
--------
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.
--------
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.
--------
We provide a defintion of joint to include the notion
of a collective goal ...
Joint action:
An event involving two or more agents where the agents’ actions have a collective goal.
Is this good enough? I’m not sure it is.
But note that it is agnostic about mechanisms ...
Our acting on a shared intention is one way of for our actions to have a collective goal;
but maybe there are others ...
--------
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.
--------
For us to have a \emph{shared goal} $G$ is for $G$ to be a collective goal
of our present or future actions in virtue of the facts that:
\begin{enumerate}
\item We each expect the other(s) to perform an action directed to G.
\item We each expect that if G occurs, it will occur as a common effect of all of our actions.
\end{enumerate}
(Compare \citealp{Butterfill:2011fk,vesper_minimal_2010}.)
--------
The objection will seem unanswerable if we assume that all joint actions
involve shared intention and that Bratman’s account of shared intention
is correct.
--------
But I’ve argued that the evidence suggests that children in the second and
third years of life are not in the business of coordinating plans, so Bratman’s
account of shared intention does not characterise the way they understand the joint
activities that they participate in.
For this reason we should not accept that all joint actions
involve shared intention and that Bratman’s account of shared intention
is correct.
Instead, I think we can allow that there are joint actions which do not involve shared
intentions but instead involve shared goals.
It is these joint actions that we will need to appeal to in explaining the emergence
of mindreading and referential communication.
--------
Our next (and last) question ...
‘the basic skills and motivations for shared intentionality typically emerge
at around the first birthday from the interaction of two developmental
trajectories, each representing an evolutionary adaptation from some
different point in time.
The first trajectory is a general primate (or
perhaps great ape) line of development for understanding intentional action
and perception, which evolved in the context of primates’ crucially important
competitive interactions with one another over food, mates, and other
resources (Machiavellian intelligence; Byrne \& Whiten, 1988).
The second
trajectory is a uniquely human line of development for sharing psychological
states with others, which seems to be present in nascent form from very early
in human ontogeny as infants share emotional states with others in
turn-taking sequences (Trevarthen, 1979). The interaction of these two lines
of development creates, at around 1 year of age, skills and motivations for
sharing psychological states with others in fairly local social interactions,
and then later skills and motivations for reacting to and even internalizing
various kinds of social norms, collective beliefs, and cultural institutions’
\citep[p~124]{Tomasello:2007gl}.