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The Interface Problem: Motor Representation vs Intention
anarchic hand syndrom from dr strangelove (Della Sala, Marchetti, & Spinnler, 1991)
anarchic hand syndrom
‘The right hand frequently carried out complex activities that
were not willed by G.C.
These activities were clearly goal-directed and were well executed, but undesired by the patient, who used her left hand to try to stop them.
For
example, when the patient had a steaming cup of tea in front of
her, the right hand proceeded to pick it up and bring it to her
mouth, even though the patient knew that it was too hot and had
just said she would wait a few moments until it had cooled.
Nevertheless it needed the intervention of her left hand to
replace the cup on the table.’
(Della Sala et al., 1991, p. 1114)
Believe it or not, this rare syndrom tells us something important about why
all humans act. Or so I will attempt to show you (much) later in the course.
Challenges unity and therefore the idea that there is a single coherent body
of reasons that are known.
Go really slowly here. Drive it home by saying it again.
(Do not comment, just repeat)
More background on AHS:
(Mylopoulos & Pacherie, 2016, p. 7): ‘Typically the result of lesion
to SMA or anterior corpus callosum, AHS is a condition in which patients
perform complex, goal-oriented movements with their cross-lesional limb
that they feel unable to directly inhibit or control. The limb is often
disproportionately reactive to environmental stimuli, carrying out
habitual behaviors that are inappropriate to the context, e.g., grabbing
food from a dinner companion’s plate (Della Sala 2005, 606). It is clear
from many of the behaviors observed in these cases that the anarchic limb
fails to hook up with the agent’s intentions.’
Everyday counterpart is action slips.
action slips
ex Norman’s croutons
Norman (1981); Mylopoulos (2022)
Having an intention is neither necessary nor sufficient.
‘both mundane cases of action slips and pathological conditions, such as apraxia or anarchic hand syndrome (AHS), illustrate the existence of an interface problem.’
Mylopoulos and Pacherie (2016, p. 7)
Jeannerod 2006, p. 12:
‘the term apraxia was coined by Liepmann to account for higher order motor
disorders observed in patients who, in spite of having no problem in executing
simple actions (e.g. grasping an object), fail in actions involving more
complex, and perhaps more conceptual, representations.’
Can people with ideomotor apraxia form intentions?
So time to say what it is ...
The interface problem: explain how intentions and motor representations, with their distinct
representational formats, are related in such a way that, in at least some cases, the outcomes they
specify non-accidentally match.
‘both mundane cases of action slips and pathological conditions, such as apraxia or anarchic hand
syndrome (AHS), illustrate the existence of an interface problem’
(Mylopoulos & Pacherie, 2016, p. 7).
Two collections of outcomes, A and B, \emph{match} in a particular context just if, in that context,
either the occurrence of the A-outcomes would normally constitute or cause, at least partially, the
occurrence of the B-outcomes or vice versa. To illustrate, one way of matching is for the B-outcomes
to be the A-outcomes. Another way of matching is for the B-outcomes to stand to the A-outcomes as
elements of a more detailed plan stand to those of a less detailed one.
image is from dall-e
Imagine that you are strapped to a spinning wheel facing near certain death as it plunges you into
freezing water. To your right you can see a lever and to your left there is a button. In deciding
that pulling the lever offers you a better chance of survival than pushing the button, you form an
intention to pull the lever, hoping that this will stop the wheel. If things go well, and if
intentions are not mere epiphenomena, this intention will result in your reaching for, grasping and
pulling the lever. These actions---reaching, grasping and pulling---may be directed to specific
outcomes in virtue of motor representations which guide their execution. It shouldn't be an accident
that, in your situation, you both intend to pull a lever and you end up with motor representations
of reaching for, grasping and pulling that very lever, so that the outcomes specified by your
intention match those specified by motor representations. If this match between outcomes variously
specified by intentions and by motor representations is not to be accidental, what could explain it?
The Interface Problem:
How are non-accidental matches possible?
Motor representations specify goals.
As we have just seen, motor representations specify goals.
Intentions specify goals.
And of course, so do intentions.
Some actions involve both intention and motor representation.
Further, many actions involve both intention and motor representation.
When, for example, you form an intention to turn the lights out, the goal
of flipping the light switch may be represented motorically in you.
The nonaccidental success of our actions therefore depends on the outcomes
specified by our intentions and motor representations matching.
Intention and motor representation are not inferentially integrated (because representational format?).
Two outcomes, A and B, match in a particular context just if, in that context,
either the occurrence of A would normally constitute or cause, at least
partially, the occurrence of B or vice versa.
But how should they match?
I think they should match in this sense:
the occurrence of the outcome specified by the motor representation would
would normally constitute or cause, at least
partially, the occurrence of the outcome specified by the intention.
On the other hand, if there are never non-accidental matches
then good luck getting off that spinning wheel even if you are right
about the lever
Now we have to ask, How are nonaccidental matches possible?
If you asked a similar question about desire and intention, the answer would be
straightforward: desire and intention are integrated in practical reasoning, so it
is no surprise that what you intend sometimes nonaccidentally conforms to what you intend.
But we cannot give the same sort of answer in the case of motor representations and
intentions because ...
Intention and motor representation are not inferentially integrated.
Beliefs, desires and intentions are related to the premises and conclusions
in practical reasoning. Motor representations are not.
Similarly, intentions do not feature in motor processes.
Failure of inferential integration follows from the claim that they differ in
format and are not translated. But I suspect that more people will agree that there is a
lack of inferential integration than that they differ in representational format.
(must illustrate format with maps).
So this is the Interface Problem: how do the outcomes specified by intentions and
motor representations ever nonaccidentally match?
