II
minimal models for acting together?
These and other contrasts invite the question, What distinguishes joint actions
from things that we do in parallel but merely individually?
shared intention
What is shared intention?
‘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.’
(Carpenter, 2009, p. 281)
What is shared intention?
Paulus et al, 2016 figure 1
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.)
Paulus et al, 2016 figure 2B
goal != intention
A goal is an outcome to which an action is directed:
the grasping of a mug or the writing of a paper, for example.
Importantly, a goal is not an intention.
An intention is a mental state whereas a goal is an outcome, so a state of affairs.
And not usually a mental one.
[It’s easy to miss the distinction between goals and intentions,
perhaps because in talking about goals you may reveal much about what you intend.]
Garbarini et al, 2014 figure 3 (part)
To test this conjecture, Corrado Sinigaglia and I teamed up with
Francesco della Gatta, Francesca Garbarini and Marco Rabuffetti.
We adapted a bimanual paradigm, the circle-line drawing paradigm, which has been
extensively employed for investigating bimanual interference (Franz et al, 1991).
When people have to simultaneously perform noncongruent movements,
such as drawing lines with one hand while drawing circles with the
other hand, each movement interferes with the other and line trajectories
tend to become ovalized. This “ovalization” has been described as a \textbf{bimanual coupling effect},
suggesting that motor representations for drawing circles can affect motor representations
for drawing lines (Garbarini et al. 2012; 2013a; 2015a; 2015b; Garbarini and Pia 2013;
Piedimonte et al. 2014).
[repetitive] Suppose a straight line and a circle are being drawn at the same time.
The straight line will exhibit ovalization.
This ovalization is not just a consequence of pysiology, for you find much the
same ovalization when someone is merely imagining drawing the circle, and in patients
with anosognosia for hemiplegia.
Instead, the ovalization is a sign that the goal of drawing the two lines, one straight
and the other circular, is being represented motorically.
della Gatta et al, ‘Drawn Together’ Cognition 2017
What happens if you distribute the actions across two people, so that a confederate
draws the circles while the participant draws a line?
We contrasted a Parallel Action task with a Joint Action task.
These tasks differed only in the instructions given.
ALL CL CONDITIONS
Draw lines.
While doing this, look at the screen in front of you.
And that was actually what we found.
Our hypothesis is that interpersonal motor coupling may occur when an individual is acting
unimanually, providing she is acting jointly with another and not merely acting in
parallel. This is because in joint action, but not in parallel action, an individual could
represent motorically the collective goal of drawing both a circle and a line even if she
is actually only drawing a line. Somewhat as in the case of individual bimanual action, so
also in joint action: the motor representations of one hand’s drawing can influence the
motor representations of the other hand’s drawing. One difference in joint action, of
course, is that the hands belong to different individuals.
della Gatta et al, ‘Drawn Together’ Cognition 2017