This is the Convergent Science Network podcast. Leading researchers in the domain
of neuroscience, brain theory and technology are interviewed by Paul Verschoor and Tony Prescott.
This is Paul Verschoor with the Convergent Science Network podcast and I'm here with Vincent Hayward.
Welcome, Vincent. Vincent, who spoke today at our BCBT 2018 summer school.
So, Vincent, your focus in your research, I mean, also coming from engineering, is very much haptics.
And do you think haptics is a specialized sense, or do you think it's sort of
full of the same general principles of organization that you might find in other senses as well?
Yes, that's a complicated question.
So my answer is like yes and no. It's a very easy answer.
In the what I think is the case is that the.
There must be general principles that are common to the senses. There is no doubt.
It's not an idea, like the Gestalt held that view, that you had the perceptual principles, and they.
Spent many years actually finding them, and they do exist.
This morning we talked about illusions, for example, and quite a number of visual
illusions have direct tactile counterparts, but many don't.
And so that indicates that actually the,
haptic haptic so in the sense of the mechanical relationship we have with the
world really occupies a specialized,
niche in our being if only because it's the functions that make us,
habilis.
Animals that can manipulate or walk or run efficiently.
But the haptics is of course not special to humans. uh worms have it even paramecium have it uh,
It's so unfortunate that actually it's a topic that's so ignored when it's in reality so important.
But now you are a biased observer of that. Yes.
From an evolutionary perspective, you could argue that the very first modality is touch.
It's mechanosensing and chemical sensing. Yes.
Well, I don't know if we know much about really early animals,
but we do have them, like paramecium.
It's been there for a long time, I suppose.
If you want to radicalize that, you could also say, look, molecular interactions
are all about shape. Shape interactions are all about shape touching.
So it's most fundamental level, even at that sort of pre-single-cell organism.
We talk about touch, shapes colliding. Colliding, yeah.
So the question should be turned around and we say, well, maybe it's the other
monalities that have been built on the principles of touch. Could be.
So would you find that they're useful? But I'm not sure if there's a reason to have a...
First of all, there's no hierarchy. quirky, like often it is discussed.
There is no sense that's better than the other.
They are there for a reason.
So touch is not better than vision, or it's just touch is touch,
and vision is vision, audition is audition.
And in the history of the development of animals, I'm not sure that one came
before or after. I don't think that's an important question.
Very early organisms were sensitive to light.
Plants are sensitive to light. I mean, there's very much an anthropomorphic
projection we put on having to,
you know, put things in a sequence as if… Yeah, but also finding a heuristic, right?
And sort of try to find a way through the complexity of the organization of
perceptual systems. Yeah.
So you can say, well, look, touch is like the principle of touch can be generalized,
to let's say a particular condition. Well, one we discussed earlier is constancy.
That's a really, really fundamental principle, which is equally important in all modalities.
I mean, if you didn't have constancy, your whisky would really taste terrible, because,
you would have all the different chemical reactions, or anything you looked at would be a big blur.
So that's really a common need. But now, for instance, if you take a worm,
which will also have a sense of touch, Right?
I assume. A very good one. Yeah.
To what extent would its organization generalize to how, for instance,
our sense of touch, that laminal fingertip, is organized?
Well, that's a long jump from the world. Yeah. So the primate finger that we
have is obviously very late in evolution.
This pad. Of course, many animals have pads, but putting a pad at the end of
a highly movable organ is really a good invention.
Ursidae and felines have something like that, or rodents for that matter,
but the primate has really pushed the sophistication of that organ to a great
limit. It has incredible.
Mechanical properties. Like one of them, for example, which is,
surprising like most mechanical solids they when they are compressed,
modify their global behavior like if you and tissues are not no exception like
if you pull on a tendon it becomes stiffer.
But somehow the fingertip doesn't you can push as many put any load on the fingertip
it'll regain or keep its same elasticity.
It's really amazing, actually.
You can do the test with me, actually.
You put like a very small load on your finger and you can see how it moves by
a couple of millimeters.
And I push always all my might and it moves the same amount.
Exactly the same. And I span here maybe three orders of magnitude of load difference.
But the mechanics have essentially remained invariant.
That's a really good property. So when does that emerge in evolution?
Do you know of examples of more primitive organisms that would show similar?
Yeah, I think felines don't have that.
I looked a little bit at the feline pads, which are really good running machines.
They don't need that. It looks like a primate sort of feature,
that really makes the prehensile extremity,
so good at holding and sensing at the same time.
So, it's a little bit unclear whether the principles are shared, right? But now, can you.
Enumerate then the principles of haptics that make it really a highly reliable sense?
So you would have to reorder the organizational principles of ethical well there's
something I think it is rather,
special to touch is the very clear,
lateral,
organization which seems to be a a consequence of the fact that.
The ambient field that gives you a mechanical sensation is not local.
So that's something very profound. Explain that.
Yeah. When you look at something or you hear two sounds,
which have two points in space which are very close, they create a signal on
your retina that is also very close.
Up to the diffraction, essentially.
So it's very, very small. And a bit of also the blurring in the retina,
but by and large, that's something you can rely on.
Things that are close in space are close on your retina.
In the auditory space, sounds that are very close also are very distinct,
and you can actually take them
apart even they are very close it's not the case it cannot be the case in haptics
and the reason is because we are made we are a solid actually viscoelastic solida
and any change in the boundary condition has far away consequences,
and so it.
So, small things are not local.
A simple example, you read Braille. So, it's a small point. Let me close the door.
Because the rest is bloody glory.
Yeah, so let's go back a second. Maybe you'll restore the audio.
Yeah, let's take an example. Reading Braille, of course, it's not a spontaneous
activity, but it's something you can do. And...
The dots are very small, so you would intuitively believe that actually it's
because the dot makes a very small contact on your finger that you feel it being small.
But if you actually look at the mechanics of that interaction,
you realize that the braille dot has mechanical consequences that are like five
or six millimeters in size.
So it's a huge patch of skin that is actually disturbed by the very local contact.
Of course, consciously, all you feel is that tiny little thing.
But what comes from the periphery is like a really blurred, enormously blurred signal.
And that's static. Now, if you have dynamics, which is actually the province
of haptics, things that are dynamic and move,
then you have dynamical effects in your body, which, to simplify it,
could be thought of as waves, like propagation of signal.
And small events in time and space become very large things in your body.
But i don't so so the yeah
so the consequence of that is that the neural organization
has to be coping with that non-locality principle
neither in time or space to have sufficient
non-locality because there is topography there's mechanical coupling and there
are distance relations that are fixed right so if you talk about let's say the
number some millimeters of spread of a mechanical and what the information due to a braille pixel.
That's a constant that's defined, that's given by the mechanical properties of the tissue, right?
So in that sense, it's the same thing as having some sort of retinotopic organization
that maps distance or proximal locations in visual space to proximal locations on your retina, right?
So, I thought you were suggesting that the haptic system was not following such
a topographic relation.
Ah, no. So, what I said is, in order to achieve sufficient acuity,
then the neural system has to have inputs from large regions.
And that has consequences on the way, apparently, the early stages of somatization are organized.
Then I can argue in the retina, you also see how it compresses the responses
of many of the receptors into single neural responses.
Yeah, so that reduction principle you are talking about is obviously shared
by all the sensors. I mean, what's the...
You know, the guy who works on the frog retina.
Is it Maserano maybe? No, no, no, in the 60s. Yeah, anyway.
The classic work that the frogs, I don't know, that's more the tectum, okay.
Yeah, the idea that actually the organs detect the most relevant signals and reduce them,
compress the information essentially to only what is relevant to behavior.
That's an old idea. Of course, it's true also in touch.
If you felt everything that your body experienced, then the mechanical world
would be completely indescribable. It would be an incredible mess.
It wouldn't be surfaces,
textures, materials, shapes, weights.
I mean, the example we gave at lunch, you hold a cup and it has a heaviness.
You can hold it in a hundred different ways and it's the same heaviness.
But that's invariance. That's invariance. Yeah, but in order to achieve that
perceptual performance,
the only way is that very early in the nervous system that information collected
for very large regions are integrated.
And maybe also across modalities. And also across modalities.
But remember, we started out by trying to rank order the organizational principles
of haptics. Now we're talking about some sort of topography of the organization
of the receptors that you feel is unique.
In terms of the raw periphery, of course the skin is the seat of the largest number of inputs,
but you should also account for the muscles.
And also, there is a tendency,
which is very confusing, and still confuses me, in thinking that actually somatosensation
is like separate channels, like proprioception and tactile inputs.
But mechanical and the neural reality is not so simple.
For example it's something I learned from colleagues in Sweden also like Melanie
Hedin if you close your hand you do this you feel your fingers moving but the
neural reality is that you have,
thousands of spikes coming from the entire hand and from the skin not from the
muscle that actually tell your fingers where your fingers are,
but at the same time you can actually touch your hand here and separate out
the perturbation given by this object and the perturbation given by my own movements.
So that's actually an old idea.
But the idea that actually the skin is all tactile and muscles are only proprioception
is certainly untrue. and and and um.
And vice versa. That's something I didn't speak about this morning,
but a study done by another colleague of mine, Jean-Rito Nard, who is a former student,
who was working with patients with reattached hands,
after having lost a hand in a trauma, and it's being stitched back.
And as you know, when the procedure is complete, then the reattached hand has no sensation.
Even though the nerves may be transmitting signals, they have no significance.
So you can actually bang on the hand and touch it, and there's no sensation attached to it.
And then, and then Tona and his students, they tested patients to see how fast they would recover.
Okay. So they had the, this patient actually ranked textures from coarse to fine.
And to their astonishment, like days after the operation, they could do it.
But was there dynamics to the effect? Yeah. So, right. Right,
so that's why I came in, and we know that was pretty amazing, actually. No skin.
And then what happens is actually the mechanical signal that,
mechanics that are elicited by friction, frictional noise, if you want,
let's call it this way, propagates practically in the entire arm.
So there's a lot of other sensing options possible.
And we replicated that study by.
Anesthetizing the hands of healthy participants and they still could do it and
so so that's that's really interesting it it really shows that this uh.
Intuition we have that it's because we touch a place something at a particular
place that's where the interaction is, is really a naive conception.
The mechanical reality is many times more distributed.
There are two problems we have to solve now.
One, mechanosensing is not limited to the skin.
This is point number one. That raises the question, what is the realm of the
mechanosensing, because that's in the end what haptics is about,
right? That's about the mechanosensing.
So this might include the stretch receptors in your muscles and so on.
It does, yeah, most definitely.
It might also have, let's say, low density of sensors throughout the organs and so on, right?
Misantery and... So where do you draw the boundary?
I don't... You don't. Yeah, so that's what I was trying to get at.
The textbook view likes to draw boundaries.
You know, proprioception, it is this set of receptors, and tactile sensation, it is that set.
So if you want to prove that you can, you can always come up with examples where
that works, but you can also come up with as many counter-examples.
If we look at the somatosensory cortex, was then the old view of Penfield,
of the homunculus, also restricted?
And so if we take the perspective that you now advance, which is more inclusive,
what would the homunculus look like? Would it change a lot?
Well, the homunculus… Add dimensions to it. I would add dimensions to it.
There is no doubt that if you follow the neural pathway from a place in the
body and through the different neural stages,
you do observe a correspondence between body regions and cortical regions.
There is no doubt about it. but the more modern views have actually shown that
first of all these cortical regions are many and.
Second, they can change, whereas your body doesn't.
Third, that they can also be involved in other things than tactile experience, like movement.
That they have bilateral, very surprising bilateral representations.
That's something that I was often ignored.
It's like if you drive a particular finger and then you illuminate the pits
of the cortex, you also drive the cutter side.
Why? I don't know, but it is an empirical finding.
It's not really complexifying now, right? So basically you're saying,
look, it's higher dimensional than just the skin.
Yes. So let's go back to this idea of dimensions.
The textbook view is the skin has two dimensions. It's a sheet.
This morning we talked about mechanics. And clearly in mechanics,
there is no such thing as sheets. There are solids.
And solids are three dimension. dimension, and their state requires at least
6 numbers at the most basic level to be represented.
And worst of all, you need an infinite number of 6 numbers to be able to describe
the static state of a solid.
So this idea of two dimension is is is too simplified much too simplified but then,
okay it's higher dimensional but then we can also add time because silver we're
only talking about space yes so the time you mean dynamics yeah it means yeah so,
how would you include dynamics is
it basically just we are multiplying the multidimensional maps of space,
and then we have some, let's say, different time windows or different frequency
responses or what have you. Is this roughly how we should think about that?
Yeah, you could. But I tend to have a different view.
That...
The brain doesn't care much about the skin itself.
It really only cares about the objects that could possibly interact with your skin.
So that's really a very different way of thinking.
And when I say objects, I really mean the sort of mechanical effect they can create.
A good example are shocks. rocks.
In the old days, there was a tactile display that was extremely successful,
but didn't last very long. It was called the Opticon.
I don't know if you ever felt one.
So the Opticon was essentially a set of little hammers.
It didn't touch the skin, actually. They were actually at some distance of the skin.
And the display principle was actually to make them hit, collide.
Each time you have a collision, it creates quite an interesting mechanical event.
But it's of course non-local, it's waves and it's complicated,
but it's processed beautifully by the nervous system.
It makes, if you want, quote-unquote, very sharp images.
You can feel lines and motion very nicely.
But the mechanical reality is an incredible mess.
And the explanation for that is because actually your nervous system is tuned
to collisions. That's something that is really important.
As a mechanical event. And collisions, of course, have many consequences,
and it's the consequences that are sensed. It's not because it's there, if you want.
Right. But now... And there are lots... I was telling you at lunch about the example of a wood stick,
which has special mechanics, and they have been integrated in people's brains
completely seamlessly.
Yeah, but then we're running ahead of it, because we're still trying to sort
out the basic principles, right?
And also one thing that you mentioned in your talk is that actually there are
very few people working on this, right? It's not such a crowded field.
And there are very few really quantitative assessments of the response properties
of haptic sensing, right?
So you spoke of how the scale of stimulation would sort of map to different
kinds of thresholds of detection.
So what do we know about that? This relationship between sort of object size
or the scale of stimulation and the sensitivity we might have to then respond to, to stimuli?
Well, we don't know a lot.
But scale is clearly one of these information reduction principles.
Events that are short in time or localized in space are treated differently from events that are,
elongated long lasting if you want and occupy large portions like a whole table
it's very different from a,
fabric I don't know how to say that more precisely but.
Well, that's the example of the elephant, right, so to touch a small object
or elephant… Yeah, the elephant is proverbial.
Of course. But there's always truth in proverbs.
And it's much the case that if you want to have the shape of an elephant,
then you have to touch it with your whole arms.
And it's really the displacement that gives you the relevant information.
But if you're manipulating a needle, then it's pretty useless.
What matters is actually the way the skin is bent.
But in this way of haptics, what do you feel has been, if you look at the whole
set of experiments performed in this domain, which was quite a bit,
but you know all of them. It's quite a bit, yeah.
Which of these have shed the most light on the organization of this system?
Which is really the crucial experiment that was a breakthrough,
if you want, in understanding of haptics?
I will have a rather arrogant opinion. Let me guess. in believing that there's
been none so far okay really important uh that will you know why is that,
Because it implies that you have some expectations. Yeah, exactly.
The reason for that is actually a lot of the so-called basic understanding of
touch were actually drawn from findings in vision.
But as I've tried to explain,
the domain is so different that you can always twist your brain into believing
that touch is like vision, it has many things in common,
but the number of cut examples is so large that I'm convinced now it's actually
a very misleading intellectual approach.
But this is also annoying, right?
Because there are loads of experiments that have been performed and published
in haptics, and there are all these micro-observations around something that
we don't really comprehend yet.
It's almost like a random sample. Yeah, yeah, yeah, certainly.
So what are we missing then, in your opinion? what's what uh
uh yeah i did write a
grant on this topic uh that was
about 10 years ago now almost and and and the uh basic argument is that in in
um in somatosensational touch there was nothing like like like in vision in
the sense like uh kondring and mar,
are outlined, and then the neural coalescence that were found from the theoretical consideration.
And so I promised to do that, actually.
Yeah, but that's a knowing argument, right? Because you said,
we don't want to compare to vision. And now you say, well, we've made a bunch of progress in vision.
Yeah, so we have to do the same in audition. Well, in audition too, actually.
But maybe the progress in vision is more illusory than real.
Maybe. A lot of people are very busy. But if you really ask,
like, okay, what are the...
The fundamental principles that really allow us to comprehend the system and
how this works? Well, there's a litmus test, actually.
After all these centuries of research, there are pretty good artificial vision systems.
Whether they are biologically relevant or not is another question, but they do function.
And many of them actually have drawn, consciously or not, ideas from how natural vision operates.
I disagree, but go ahead.
I didn't say all, some.
But when you look at the state of the art of artificial touch,
it's really a terrible situation.
Sure. There's no comparison.
That's tricky because you can, of course, also say like, well,
we made great progress with building microprocessors, right?
Yeah. So we know about cognition.
No, that's not what I mean.
There are just no market drivers for advanced haptic systems.
There are lots of them. There are market drivers for cheap vision.
Yeah. I'm not sure I find it a very convincing argument.
No, it's not an argument. It's an observation that the computer vision actually exists,
but computer touch is essentially non-existent.
And if you look at most of the activity in that domain, I mean,
actually, it's a survival copy of a visual.
Right. Okay, so the bottom line would definitely be that you're saying,
well, we're actually really in the dark. We're in the dark about.
Yeah i would uh would agree with that yeah then where
where should we start because what you present one experiment that's
always extremely interesting where you had these these actuation arrays
that you either stimulated in uh
in sync so they're oscillating at some frequency i don't remember which one
but either they were they were synchronized or they were um not synchronized
right so you said actually they were out of phase right yeah which led to two very different,
experiences from the touch perspective, right?
So one, the first one, synchronized, it's like a solid or like a solid surface.
And the other one feels like there's some viscous media. It's the other way, but...
This is very interesting. But now we bring in dynamics, right?
Now we have time, we have movement, change. Right.
So is that the thing that we've been missing? Because also, in vision,
you see the same thing. Vision is very much analyzed in terms of spatial maps,
hierarchies of spatial maps.
If you look at therapy, that's what it's all about. How can I learn hierarchies of spatial maps?
And I have lots of wires between the maps, going back to Rosenblatt and then,
Ptolemaic and whatever.
And then, of course, we know anatomically, actually the wires between layers
in cortex or regions in cortex, V1, V2, and so on, is rather limited. with it.
It's less than 3% of your synaptic volume.
So when there you see that the approach taken is sort of orthogonal to what
we understand of the biology.
But is this maybe a key insight at which you say, well, maybe we have not opened
up enough to rethink what that haptic code should be.
And maybe the haptic code is much more temporal than spatial.
Would that be an entry point for you? Yeah, that would be correct.
The temporal performance of touch is excellent.
It's almost a driver's edition.
Actually. And evidence is accumulating that if you want, the property of objects that are,
in contact with your body are acquired through timing.
I'll give you a simple example of that.
Actually, it was Flanagan and Johansson, they put the hypothesis that actually,
how do you know that you're actually touching a table?
Well the code is simply because all the afferents in ad regions are responding
at the same time, from the first spike. like. It's a great idea.
And it's not important that they are all from the same place,
it's because they are at the same time.
And it's probably true. I'm pretty sure that… Let's follow this,
right? So now I'm tapping the table.
Okay, so I have a synchronized response in my fingertip.
This thing goes up to my enthalomus and from there into the cortex.
How many processing steps?
How many? How many processing steps? Before you feel it? Before I'm going to say, oh, it's stable.
One in the brainstem, which we commented
this morning is probably quite sophisticated. Cuneus, right? Yeah.
One in the thalamus. Nobody knows. There's almost no study on the uh...
Function of the thalamus in somatosensation, almost none. But it should be like
the others, more specialized.
Yeah, there should be something like the superior colliculus,
but for touch, somewhere. It's called VPN.
Yeah, it has a name, of course, because the anatomists have identified it.
But the function is a complete mystery, or a terra cognita.
And then you have the cortex, And then you have the primary area,
S1, which actually has the subdivision, and then you have S2,
and then maybe something, I think there's something like S3,
I'm not quite sure, and then it becomes Pareto.
And that's probably where the integration really takes place.
So, if you can count, no, we can go back and count, it's quite a few stages, actually.
But based on what you're saying, then, the real experience sits in the parietal
area. Oh, I don't know. No, no, no, that's where I went.
And from there, we might then speculate, because that's what this is all about,
that it's right then also indeed a multimodal construct. For sure.
Yeah, lots of examples of that, including some of my studies.
Do we know anything about the latency between this touch and 20 milliseconds yeah.
The experience? Yeah. In the parietal cortex?
Probably longer. Yeah. It's 20 milliseconds to the primary areas. Okay.
And then I don't know. I could know. I don't have the number in my head now.
But I have a former colleague who has actually done some really interesting
studies recently on that using high-performance EEGs. Okay.
So now then, the other thing you pointed to, and still, again,
now we go all the way back to the periphery, is how already the periphery is
being really manipulated,
how the viscosity or the rigidity of the skin itself at the fingertip is of direct relevance.
Direct, yeah. To what you feel. Both the control of grasp and the touch sensation.
Yeah. So, what you were saying is that depending on how liquid or how moist
the skin is, of course, slippage will be different.
But for some reason, that grass is automatically tuned to the wetness of the skin. Yes, it has to.
So, why does it have to be like that?
Well, I don't know if it has to be like that, but we're living tissues.
So, we have to have water.
And the repertory of materials is not so great.
I mean, you have collagen fibers, and you have keratin, and you have a certain
set of possible materials you use.
That actually have the structural properties for making an animal.
So that's what you have. And they are good or bad, I don't know,
but they are what they are.
And it's likely that the neural system co-evolves to deal with that because you don't have a choice.
Well, but look, it sounds good. it and then
also you brought robust control right but this
is based now on a number of assumptions that i think we
should be clear about because in some sense now we get complexification because
you're saying well i i only have touch and touch is mapped to grass and for
some reason i adjust the grass force to the friction force i have on my skin
yeah which in turn depends on how wet my skin is.
And not only on the wetness, but the material. Of course. If it's glass or wood.
So that loop is closed. Apparently, it's not a loop.
Much of it is open.
Even worse. Now your trouble is even greater.
Because to make that work, I must sense how slippery That's where my skin is. Right.
So you look at what you're...
And if you don't look, then you have this over-powerful grip.
So it means the controller here is basically lacking any further information.
It's the worst case, yeah. Maximum. Or something slippery, yeah.
Like if your life depends on it, that's uh you know you're grabbing a handle
you're not going to group it for you just go and right,
okay so you're saying this fine tuning of control is learned that because it
depends on other modalities and would depend on yeah it it is learned um i mean
i don't think it's innate i mean some of it is innate as far as i can tell okay
yeah but you went in a direction that that,
Actually, that would be a good place to look for innate.
What I was thinking, it actually creates great opportunities for control because
I can also say, okay, if I have to slip, if I want to control the slip of an
object, because we don't always hold everything in a rigid way,
we also have to slip to also reduce damage. Not only we...
Actually, it's a very interesting point nobody discussed. because most of the
time you don't want to have your stable contact unless you are holding a cup or eating something.
But many of the cases, you don't want to actually sleep or being quite mobile.
But the mechanical relationship, as we saw this morning, is incredibly varied.
So the motor loops have to be able to deal with that very large variability
and make sure that sleep happens.
Exactly. The other thing that we didn't talk about, in other words you didn't
mention, if I'm over-conservative I'm damaging my skin.
Oh, you do, yeah. Which is a huge cost. Which is pretty bad,
yeah. So it's actually not even that the error is on one side only,
like the open drops, the catastrophic failure. You can get cuts.
Also, there's an error at the other side, where it leads to self-damage,
which would actually maybe be a higher cost.
Yeah, self-damage happens, actually, mechanically speaking, in two possible ways.
Either you have abrasion so it means that you have.
Surfaces that are sharp edges and you slip against them actually it's the only
case or you can have an edge which is basically a simplified version of abrasion,
And so these are really extreme cases. In a natural object, you have thorns,
of course, which have been designed for that.
But most objects are innocuous, like stones and wood, unless they have thorns.
And of course, in the modern world, you have metal sharp and,
Well, it leads to, also, if we compare it in all other modalities,
no, not all, yes, well maybe not all, there is always an automatic calibration to intensity.
Yes, that's a tricky question.
That's maybe the realm we're in,
because do you want to normalize friction forces that you're exposed to?
And do you want to do that by sensing the actual friction forces or actually sensing,
the moistness of the skin right to make sure you sort of recalibrate continuously
when you say sensing you said something very.
Precise you mean you had a sensor you mean for the first time but you don't
have any sensor for moistness or you have no sensor for friction this is where I disagree with you,
For instance, we do know that the sweat correlates with resistivity.
This makes it therefore, in theory, possible to measure resistivity.
How? Which receptor would do that?
Well, the resistivity of the skin would have electrical consequences, right?
Oh, you mean new properties of ion flows might be affected.
Might the speed to which I can respond will be affected. Why not?
Wow, that's a pretty daring hypothesis.
Moreover,
the field is only two people by itself. it's worth thinking about,
actually because moistness is definitely a sensation it has it's like,
you know it's like a kind of a color if you want it has it's and it's really
actually interesting to,
see how we actually experience wetness or presence of a film of water between
your hand and the object object.
It seems like there are two ways to do it.
Either the object is impermeable, like we said this morning,
like a glass surface, where you have some kind of lubrification.
And you have another class of objects which is very common, they are porous,
so they actually diffuse water.
And in the two cases, they are correlated to thermal behavior.
So the thermal bridge, which is made by an impermeable surface,
is totally different from the thermal bridge made by a fabric.
And so it's this combination of mechanics and thermal input that creates the sensation of wetness.
Also. Yeah. Actually, in VR, it's possible to make things that feel wet if you
do recreate artificially the thermal profile.
But maybe the answer sits in the keratin itself.
You gave this example where you say keratin changes its viscosity.
Yes. well yeah it's a stiffness it becomes very stiff very soft but um.
This will again depend on how much moisture there is.
So the speed to which this changes will tell you implicitly about moisture.
Would you agree with that? Completely. So didn't we say the same thing about
that? Completely, yeah. Because then… That's one aspect.
Yeah, so that would be the tribology, the way the skin slips and drags on the object.
And the second is the thermal behavior. So you have two, and the two correlated
will give you a possibility to estimate the water content.
And as I said, you can do it in VR quite easily.
I mean, relatively easily by modifying the temperature of a surface according to certain profiles.
And then you do get pretty nice. It's interesting, because in all other modalities,
issues of gain control are very central.
People spend a lot of time... Oh yeah, I know what you mean.
Like in Audition, it's tremendous.
It's like five orders of magnitude of gating mechanically and neurally.
It's interesting for hefty... The gain control...
Because that's what we're talking about. Yeah, so the dynamics in touch is about,
if I recall, five orders of magnitude.
So from the smallest load to the biggest load, if you want.
And it does have this log profile, if you want. Otherwise, you would not have
all these orders of magnitude. Right.
But the notion of intensity is a slippery one in touch. actually.
You can talk about the intensity of a vibration, you can. But why not?
Well, it can be slippage or force. Yeah.
Well, force is a very misleading idea.
Force only made any sense when you have a point mass.
There's no point mass, as far as I can tell, in this room.
One of those examples, you were pressing on the table. So what you have,
in mechanical, in theoretical mechanics, you talk about, you don't talk about
force, you talk about load.
So it's a very different idea. It's also measured in Newton.
But load is something which happens on a domain, okay, not at a point.
And so the load, and I don't think the force has any representation.
In this is tricky because
if we if we now exert force on the tabletop yeah I have muscles generating force
load activity yeah but the muscles themselves are contracting no they are they
are contracting and they are viscoelastic yeah and they change length and they
create load yes they don't create force,
I could imagine this as force yeah aha yeah but you use a horrible trick do
I yeah Yeah, you put your finger on an object that is completely rigid. Yes.
And then you average out all the interaction and you call it a force.
Isn't that what experiments are about? Controlled conditions?
Yes, for sure. But it doesn't mean that it's useful information for your… Well,
at least now we can measure what I can say now. Now, okay, I push on this surface.
There is an initial load exerted on the fingertip. Yeah. But across my whole arm.
Yes. The whole thing is firing like crazy.
Exactly. There are forces being generated in the sense that the contractile
properties of my muscles. Gold organs.
I can measure as forces.
Oh, there are loads there, actually. Actually, so the way I look at it is purely geometrical.
And actually, in theoretical mechanics, that's all you need.
Well, apparently not, because we haven't explained haptics yet, but go ahead. Yeah.
All you need to know is how the bodies change shape.
And the notion of force is almost an artifact.
It's like a convenience.
But it's not contradictory because I could say a set of forces adds up to load.
Yeah, but it's an infinite set. But still, if I have the controlled conditions
now, define the boundary conditions. Okay, I'll give you a counter example to this argument.
I push with a flat plate with one Newton on your fingertip and then you have this experience.
Now I take a sharp needle and I do 1 newton, you'll have a very different experience.
But from a mechanical perspective... It's a very different situation, same force.
Sure, okay, that's fair enough. But maybe what we're looking at here is a microscopic reductionist.
No, it's really what happens, you bleed.
It's not a reductionist. It's a consequence of... But if I just...
I'm talking about me pushing the tabletop, right?
Is it useful to think about the muscle fibers, because now I have millions of
muscle fibers working together, contracting or not, or relaxing,
to generate this behavior?
Yeah, so it will load. Is it useful to look at every muscle fiber from the perspective of load?
Yeah, yeah, definitely. Yeah, actually, we have a pretty nice experiment going on.
I could show it to you right now. Do you have a spoon here?
Plastic spoon? No. Anyway.
No. Yeah, exactly. So the point is that from a geometrical perspective,
if you forget this idea of forces and stuff, It's all about how the body is
in track and how some measure of the mechanical state,
of your body can inform you about the useful properties about what you touch.
An example is actually elasticity.
Now you have a hard surface and you have a soft surface here.
So if you look at it from a theoretical mechanics viewpoint,
the only way you can do it, if
we had the force, you look at the relative deformation of the two bodies.
So it's purely relative. It's only displacement. There is no load involved.
And so you apply the laws of contact mechanics, and you realize,
actually, that the information that is available to the brain is completely ambiguous.
Confounded between shape and elasticity.
And you never realize it in real life because you have a prior,
assumption about the shape of what you touch, like an avocado when you test it.
But if you organize a lab experiment where there is no such information available,
you have a perfect confound between shape and elasticity.
And that falls directly off the contact mechanics principles.
No loads in.
Involved there. Okay, I got it. But in some sense, we haven't made that much
progress yet, right? Because now we're,
still the periphery of the whole haptic interaction with the world.
And there, you also alluded towards the end a little bit to how is the brain really sensing?
How is the brain sensing these kinds of of properties of the world.
So how many... How many properties?
How many distinct sensors should we worry about?
And what do they do, right?
Oh, the sensors themselves? Yeah, as I said, you have a population of rapidly
adaptive sensors, and then you have populations of slowly adaptive sensors.
The way I think of it is that it also goes back to mechanics.
You have to have So mechanics is mostly dynamics.
The simplest dynamics are first order, or I mean second order,
I mean. You need three terms in the equation. So you have two states.
And so if you have to have a good access to the mechanical state of an object
that has two states, you need two sensors.
And that is why, and one is rate sensor and the other one is a static sensor.
That's really fundamental. metal and and and then that's an explanation why
you would have these two categories and these are these uh virginity cells uh
or the patchini is now they are kind of a a world on their own,
they are uh more in in tissues than in the skin there are some on the skin but
mostly in the in the tissues uh sort of randomly opportunistically distributed
in the hand in the entire body you You have lots of them in the mise-en-trie.
So essentially, I think of them as systemic sensors.
So they detect waves that are zipping by.
And by the way, the waves in soft tissues are very slow.
They move at seven meters per second and go over very long distances.
And so that would be a very good portrayal of why these sensors are there.
It's basically, they collect mechanical information propagating. Yeah.
They are shear waves, actually, so they move slowly.
We have new work, actually, not me, but a former collaborator of mine,
who is a prof at UCSB, has made beautiful measurements of those waves in the anatomy.
How far do they travel, these waves? Well,
I could show you a movie, but I'll do a… Yeah, if you do this,
they go very clearly all the way to the wrist.
Okay, so from the fingertip to the wrist.
Yeah, so if you put an accelerometer here, you get a very big signal here,
and another one, and another one.
And the wavelength is 3 centimeters.
And the modes, actually, we've recently had a new result. There are very few modes.
So it's a very compact representation, actually, of the dynamics of the hand.
It would seem that, actually, you'd need a function basis of 8,
a dimension 8, to completely represent the dynamics of the hand. That's cool.
So actually for my wrist, I could sense what my fingers are doing.
Yes. Well, as I said, it's a medical observation, actually.
Do you think the brain is using that? I'm convinced it does. Okay.
Actually, it was one of the projects that's ongoing is actually to have.
Phantom locations, the dynamics. So I'll show you how you can elicit them.
You do this, you slide your finger, and you record on the tabletop. It's good, actually.
You record the signal on the nail here.
Then you put it in a recording. And then as you slide your finger,
and you put the transducer that you glue to that skin here.
Okay. So if you hold your hand like this, you feel... Glue it onto the same
finger? Same finger, but a different phallus.
Yeah, close to the palm of the hand. Yeah, here, yeah.
And you go like this. Oh, yeah, so it's here. You feel the texture going here.
And if you glue it here, you feel it here. Now you organize the situation.
Actually, when the signal starts going, the minute you touch and you slide on
a flat surface, and then the sensation travels back to the fingertip,
the textural sensation.
Ah, okay. That's cool. Yeah, but it makes total sense.
Could you put a transducer anywhere?
Yes, I think so. So that's what we're going to do for that new project.
Some mechanical transformation.
Yeah, exactly. Oh, that's really cool. But now, okay.
So that's why it goes back to what I was saying, that the neural architecture
at the most basic level has to be very lateral because of that.
That's what I meant by non-locality. But then also you're saying that haptic
is much like audition because I must pick up also the resonances.
Yes, yes. in my biomechanics.
I mean, to put an extreme argument, which is wrong but interesting,
it's like your whole body is like a basilar membrane. Right, exactly.
Which is interesting, right? Because also the basilar membrane and audition,
that's interesting features, like it extracts pitch or frequency.
Yes, but as far as I can tell, no one has ever found any somatotopy,
I mean, somatotopy in touch.
Yeah, but pitch is also never really found, it's quite a discussion, but it's an invariant.
You look at an invariant of the resonance frequency.
Tautotopy is still a very important organizational principle in audition.
Yeah, but I want to provoke you even further than that, because pitch is an
invariant, a subjective invariant for here.
If we now said the whole body is a metal membrane, what would be the equivalent
of pitch for the haptic system?
Would it be something like left hand is touching stuff? Yeah,
you could say that. My foot, I can touch this end of my foot. Oh, it's the same thing.
I would tend to think that the elements of sensation in touch are really like objects, are things,
like pieces of wood or tables, people. That's what they are.
A good argument. There's zillions of papers on roughness. Oh, yeah, right. Okay?
But if you think of it a minute, if you take a piece of leather,
it has a certain roughness, and you can rank leathers.
Now you take, I don't know, concrete, okay? You have a different...
But it's not the same roughness. So the notion of roughness depends on the object.
And woods, you know, and people, Now you have smooth skins and rough skins.
So it's not a universal concept like pitch.
Which actually could argue is not universal. It really depends on the source, actually.
And so you could make the argument that actually all roughnesses are actually
qualities of materials.
Well, that's more timber then. Yes. Yeah, but timber, that's also...
I used to dab a little bit in psychophysics. And so the joke is like, what is timber?
So you remove intensity, duration, pitch.
And dynamics, and what is left is timber.
But this is an interesting thought experiment to say, okay, if we move away
from vision and think more about the dynamics of an auditory system,
then now this starts to have interesting questions that we can pose for the
haptic system that we hadn't thought of before.
If we have purely spatial terms of the visual system, maybe that has been a misleading analogy.
I'm completely in tune with that line. You resonate with that.
Yeah. Touch can do it, you know, but pretty badly.
You have all these illusions, and because it's certainly something you need,
you know, when there's an insect, you have to whack it.
But it's interesting what you're saying, right, because that would mean that
also because but because of the constraints of experimentation,
you end up in a very extreme part of the state space of haptics.
Yeah. That sits very close to a vision issue. Yeah. But it might be really misleading.
Very misleading, yeah. Yeah, you like to have two-dimensional things because
it's easy to write papers about. Exactly.
But then you also make a plug for the nucleus cuneus, right,
which in some sense I could say you sort of co-discovered maybe with your talent.
Well, it's, yeah. Big John Powell. Big John Powell, yeah.
Because it seems to be such an essential organ, huh?
But tell me, of the whole nucleus, that no one bothered about so far?
Yeah, because the dogma, there is a dogma, which actually held that...
Actually, I might offend quite a few people on this one, but the dogma is that,
touch is very much explainable by label line theory.
And that is actually written in the textbook that you have on your shelf.
But the same holds for additionism, it's a dominant dogma. Yeah,
exactly. But in touch, you see.
So the consequence is that the physiological properties of receptors are actually
reflected in the cortex,
I mean,
you can organize experiments where that is the case, but they are so contrived
that they have no relation with normal functioning.
There's a very good example, a second point also that I'd like to make since
we're here on this topic.
This label line thing idea in touch also would like to propose that the different
type of receptors we have are frequency tuned from low frequency to high frequency
which very much comes back to the auditory example,
and so there's a paper that's quoted hundreds of times that shows that actually
you do have populations of receptors that respond to certain frequency bands and that explains touch,
But what people don't realize is that if you read the caption of the figure.
The curves are plotted at threshold, which is like the smallest detectable stimulus.
No, not the line at the threshold, which is precisely the domain where you don't
use your sensors, because they are useless at threshold. I just want to kick
in, right? Yeah, exactly. Exactly.
And if you redraw this curve at the above threshold, you get something completely different.
There's no tuning anymore. Yes.
That's problematic, yes. So, yeah, all these ideas that, you know,
you have this broad tuning. Neatly organized, yes.
But then, how did you end up finding this nucleus cuneus?
Because, um, uh, Henrik Jontel has, uh,
um, uh, spent his career on, on this, his,
uh, um, supervisor did, and, and I think the supervisor,
uh, his supervisor also, so, so his lab has a profound knowledge of,
of that organ and, and working with, uh, uh, uh, Henrik is, uh,
an incredible pleasure because it's like his apartment, you know,
he knows the place and where to put the needles.
He knows. He's got an amazing physiology.
Yeah. And so it goes very fast because of this, you know, half a century of
accumulated knowledge.
So and it's, though there's no other place I thought I can tell that can redo that fine,
So what you're saying is, this nucleus cuneus is really like almost a vessel,
a membrane or a retina. It's a metaphor.
Yeah, it's a metaphor, but it's probably more true.
It's really a neurophysiological fact.
It's first order. How many neurons does it contain?
Um...
I don't know in i don't think anybody counted them for
uh humans okay in cats it's
by the millions okay and and and uh um connectivity is by the thousands okay
so it's it's really a powerful uh and so you see the whole periphery being mapped
to that to that sheet yeah and then there was a
certain topography to it, right? It has certain domains.
Or not. You can talk about six domains, if I'm correct.
Yeah, well, you have body parts, like the pads and the regions.
But the beauty of this architecture is that if you take one single of these...
No, you take one particular region on the anatomy, then you will have hundreds,
if not thousands of neurons scrutinizing the same place.
So it's a stacked organization. See what I mean?
It's like you have the receptive fields overlapped by hundreds or thousands.
I would say in a human that's probably the case. You have a massive population
response for a very local stimulus.
And they're very large and then you have many stacked on top.
And is the response temporarily structured?
Highly, for sure. Yeah. Okay. For sure.
And it does seem that actually the spiking train coming from the periphery,
just the order of spikes is sorted out by that network. Yeah. Okay.
Which would explain things like Flanagan and Johansson hypothesized.
Like, I do this and I feel a contact because they all come at the same moment.
Right, exactly. But so would you speculate that in the temporal structure of
the population response, you are largely encoding whatever happens at the periphery?
Yes. So it's not a landline, right? Yeah, exactly.
The specificity of receptors is completely lost because these first-order neurons
collect everything that comes from all the different types of subtypes,
as called sub-modalities.
Including all these details we discussed earlier. Yeah, exactly.
So there is no segregation.
What there is is segregation of inputs, not segregation of neural signals.
Right. It's actually a conversion. So that's also the compression stage,
right? Yeah. You're compressing a lot of stuff.
It has to be. Yeah, it has to be like the retina. And it also suggests that
then this population response is invariant to the actual location where the
stimulus occurs, if the stimulus is driving this whole set of sensors.
Yeah, exactly. In a comparable way. Yeah. So, yeah.
And that's a consequence of the mechanics I was speaking of.
It's beautiful. And that is why all animals have it, even a crocodile,
it has all these scales and they have to be integrated into one single prey.
So would you say that's the most primitive representation of the periphery of the body as the nucleus?
Yeah, I would say the body is not represented, what is represented is the object that can.
Right, it's the interaction of the body with the outside. It's really the possible
interactions, yeah. Okay, I understand.
Like sharp things or small things. Including with itself, the body touches itself. Yeah, for sure.
Which actually I can demonstrate right now. There's beautiful illusions about
this. Okay, so you give me this hand here.
And you put it in this way. I do this. Now you take the other hand. You do a pinch.
And then you touch here. And then you rub.
Yeah, exactly.
So, that particular input is very unusual. You never had it before.
And you probably caused it. I mean, it made you illuminate your face immediately.
So, face illumination is a surprise. It's something that you never knew before.
Of course, the tactile input was completely normal, but that's something abnormal,
actually, in its structure.
What's the future of this research on the desnucleus cuneus? I don't know.
We applied to different programs unsuccessfully.
And for now, there are some groups of neuroscientists in the US that have started
putting multiple electrodes.
Truth. So that's interesting.
But you don't get the same information as the single cell.
And what Henrik can do is a patch clamp, which is even more fine and informative.
Okay, so it's unclear how much more we're going to learn about that structure
in the short term. Before, yeah.
It would be very... But,
Maybe it could be resuscitated if we could make a good argument that it has health consequences,
diabetes, or I don't know, something like neuropathies. It seemed to have,
it seemed like Henrik was talking about it's a possible link to Parkinson's,
which is not implausible because it's a direct,
provider of information to the basal ganglia.
Really direct.
So now philosophers over the last decades are more and more enthusiastic about
sort of embodied perspectives on everything.
And you read these really beautiful stories about it But in these analyses,
you often get the feeling that the body is taken in a very literal sense.
The body is basically bounded by the skin.
So Madan, your research, where you look really at the body as defined through
the sensors that are at this periphery. Right, so how strictly would you draw
this boundary of the body?
Well, it does seem actually that this mental picture we have of a boundary,
you know, from, if you want, our abstract understanding of physical object,
doesn't have much of an equivalent in cognition, actually.
With another former postdoc, we have this really interesting experiment going
about counting the number of sides of the skin.
So the skin normally should have two, right? In and out. Well,
it turns out that actually the number of sides of the skin is smaller than two.
What does that mean? Well, I'll give you the phenomenology, actually.
If you have an object that's rotating on the skin, it has an orientation,
and that's unique to the side.
So if you look at the skin from this side, it has a certain orientation.
If you look at it from the other side, the same stimulus will have another orientation.
Well, it does seem that actually, if you turn your hand, then the skin has only one side. Yeah.
So, then it has some sort of more global reference. Exactly,
yeah. What's the global reference?
Well, good, yeah. So, there are several hypotheses.
So, we have a north and a south, do we? Yeah, it could be visual.
It could be the visual world. That's one possibility.
It could be completely object-specified, which I think is probably a good way
to think about it really has nothing to do with the skin it's about the type
of object that can create,
these symptoms the periphery of the body on its own is defined through this
whole conglomerate of sensors,
and then resonances that then are talking
to the nucleus cuneus and whatever I
do that is sort of system systematically driving those
sensors the body seems to redefine
itself as just incorporating in what then this physical
self is yeah yeah right so if i take a
stick and as you describe it things with that stick it
will just drive the same resonance system for sure to described earlier
yeah and then the curious and everything that follows says okay that's me yeah
physically this yeah that's me yeah yeah so so so physically but is this physical
me as you showed in your more recent experiment we will publish soon you showed
that people can have very accurate predictions about what the physical configuration
is of this extension of this.
But now can we push it one step further and say I can also consider physical
me as being discontinuous.
Could I have discontinuous in the mechanical sense like having two as long as
I drive the sensory apparatus in some sense and all this multi-model I believe
that's possible yeah we actually do have a,
set of experiments going in that direction where you.
So this is more really early but we are funded by a virtual reality company
to look at that which is actually to um,
uh, uh,
illicit sensations that are owned without any mechanical connection.
The connection there is gaze.
We've shown that also at the task level. Yeah, and it seems to be pretty good, actually.
It's really dramatic. Yes, it is. more
dramatic than you can imagine because we built a whole new house of cards of
embodied cognition yeah where we say oh we're going to ground knowledge we're
going to solve the symbol grounding problem and all that stuff because there's
a body yeah but the body is embodied but now thanks to you,
it's the conclusion but the body is a construct it's not given,
that's that's yeah yeah that's what you could conclude actually Actually,
I have another contour example that's pretty good.
I have to finish the paper with Jess about this one.
You have an object and you ask how big it is.
So you have two bigger, smaller, bigger. And then you put it here on the left
side with the other hand.
And then it feels a little smaller.
So that's nothing surprising. You know, the one hand has a different calibration, if you want. Yeah.
And then we realized, actually, that's not true. It's not the hand that matters.
It's the hemispace. Ah, cool.
So you have exactly the same bias. If you put the object here and you use the
right hand or the left hand, it doesn't matter. It's because it's there.
Then you have the haptic equivalent of the Snark effect. Yes.
Right? But you also know there's a bias in the magnitude.
Right, exactly. Dependent on which hands you're using to make the choice.
Yeah. So, would you buy that?
Generalization of the Stark effect? You could, yeah. It definitely goes into the discussion of that.
But what I was pointing at is that actually, yeah, the tactile experience of
the object is really related to where it is. And constructed. Yeah.
That's fantastic. So, now you have demolished embodied cognition as well. Good.
So the other thing that you do, you also really worry about applying the science,
right? To build applications with it.
Yes. I've been doing this for a long time.
And in some sense also it's building the devices and the applications that is
also, I think, informing and feeding back into the science.
Yes. Yeah, for sure. That's a way of life.
Actually, this button here, like you have on iPhone.
Yeah, the Home button. Yeah. You know, it's actually a haptic effect. Sure.
I did publish that many, many years ago. And actually, Apple was very nice to me.
Invited me as a in a vip situation and it was great you got a t-shirt i got
a t-shirt no i got a nice one.
Well what can you do they're a trillion dollar company and they got a t-shirt
they were they were quite you know uh they called me ahead of time like two
years before the product came Oh, that's nice. It was nice, yeah. That's good.
No, I think it's a fair company.
Okay. Yeah, I'm trying. I agree.
But I think from an ethics perspective, it's not a discussion.
It's very difficult to speak of a fair company. Yeah.
Okay, so you do build these applications.
Where do you see this go? Where do you see the impact that these haptic systems
are going to have in the future?
How will they change our lives? Well, so the… The home button is gone now.
I have an iPhone 10, no more home button.
It's still vibrating once in a while, but the home button is not there.
So that's a functional, yeah, yeah. But the home button now will show up on gas stoves.
So that's when... So what's the real revolution?
How is it going to change the way we deal with the world and each other?
Well the movie theater took half a century to to really I mean it was a curiosity
for a long time and it it's only after the war that it became an important,
I mean no it did but it really exploded and so you say it will take a long time
yeah before you have yeah so you have not a specific development base,
to create that revolution, the haptics revolution?
Well, revolutions are never predicted.
I know you're a little embarrassed. But still, you can try.
So we're trying. But mundane applications, for sure, is very important.
They will come in massive.
So it's not going to be the holodeck you
know but mundane okay okay i
understand that's cool that that's also a roadmap yeah
simple simple yeah get into the real world yeah you'll also see how people will
use it yeah so we made quite a tour here sort of haptics world which is extremely
uh mysterious interesting and exciting and you've been hammering away at this
for quite a while now very systematically,
Are you doing this? So, my...
Original career goal was robotics, as you know.
And I was involved in almost the first force control robot way back at Purdue University.
What was the load? It was really force.
So essentially, you had strain gauges in the harmonic drives,
actually. It was a really nice robot.
All the ones I see now are actually worse.
I could show you a movie. It's a beautiful way. I see that robot.
It actually, you know, it tracks with, uh, uh, hard surfaces,
no problem, no stability.
It wasn't a, anyway, it worked so well. I thought it was not a problem,
you know, like not interesting.
And, and then I drifted. Uh, and then what happens is that I got,
um, a bit frustrated by the rate of progress in robotics.
Uh, I was doing like straight manipulation, a lot of software,
mechanical engineering, new structures, ultralight arms and stuff like that.
And then one day, a colleague of mine came to my office from the Research Institute
in Quebec and said, oh, I have a great idea.
I'm working on the... There's a problem.
The blind community uses Braille mostly for literacy and also for work.
And so far, the computer works were motivated by the fact that you had line
commands like Unix and DOS.
And so you had quite a lot of blind folks who would actually be system managers
and programmers because, you know, essentially lines is what you can do. It was.
And then came Windows and then boom.
Flickering everything. Yeah. It was really not wanted but it was so I said I
have an idea. Perfect, yeah.
Let's turn the window screen into something you can touch. And so we went to see a small.
Accessibility company in Quebec, which still exists actually.
It's one of the biggest in the world now.
It was proposed to make a device that would let blind users feel the screen.
I remember they gave us $5,000 to do that.
I milked some money from the space agency and and
then uh and then we actually made the stuff
it worked beautifully was a small robot that big and then you would touch it
and um and then you would actually uh feel the all the icons and uh you know
the desktop very nicely and uh and and then i i thought i was really interesting.
So I could use my engineering acumen for making it work well.
And then another guy called Bill Buxton, he was a lot of fun and he wanted one.
And then after that I never went back, basically. How long ago was that? That was actually in 91.
How did you get rid of the Windows paperclip and the paperclip troll that then would help you?
But it was really interesting, like an anecdote, but many I think those are interesting.
When you gave that device to the blind users, so in your visual desktop,
you would align the icons like in columns, like in a grid.
But the blind users that they would feel the icons and push them around they
would have you know a tactile sensation to them and they would be radiocentric and they.
So the most important would be in the middle, and the less important would be on the side.
So it was very different from a visual world. It was really a haptic world.
And then there's a lot actually of… Well, haptic is a more serial or linear search, right?
It's not linear, it's very… Or a random access, a random access to vision.
No, I think that's wrong.
It's not exactly a correct... Oh, you can tell me. Yeah.
Vision is also serial because you saccade and search, but it does it at essentially,
300 faster than the hand. No, no way.
Okay, but I can... So you can actually scan... I can go rapidly and also change direction.
I've read Russia in my... Exactly. Yeah, yeah. So the dynamics of vision are
so fast that... They compare me with the time consensors.
And in fact, you can do that in the lab. If you slow down a vision like touch, you get the similar.
In my defense, I could then say a vision could approximate random action. Yeah. Yeah.
But it's really a matter of steel. The question is that this is 35 years in haptics. Yeah.
And for some reason the field is still sort of in its beginnings. There's a lot to be done.
So what is Vincent's law if we want to make some progress here?
What law should we follow? What's Vincent's law?
Oh, in the engineering side?
In understanding engineering, you choose to have impact in this domain.
Well, that's pretty tough. Yeah, do things that work.
You never know. How does it? Overselling is a big problem. Okay.
Like in robotics, there's a lot of that, a lot of claims and very little delivery.
So get real. So the overselling is very dangerous because it makes people tired or bias negatively.
So that's a piece of advice. Don't oversell. Be, you know.
Be real. Stick to the facts. yeah stick to the fact yeah that's a good point
and then okay if i'm gonna go up to paris and um visit you four years from now
what's the one prediction you would like to see,
thoroughly tested in that time frame that's essential to your program.
So I have, yeah, I think it will be possible to reduce the, yeah,
you were asking about principles,
the, at least a certain aspect of principle to a countable amount of invariance.
And they could be biomechanical they could be physiological or they could be
mechanical or drawn from the laws
of physics but I think there is not an infinite number of them there is,
not more than the one in vision they have been well researched so that's a prediction
I could make that you could actually put them down in a you know, a discrete matter.
You're just detecting what the invariances are. Well, I know quite a few,
like the one I showed about the curvature, so that's a good one.
But there are... So you're saying
there's a handful? There will be like a handful of invariants. Yeah.
Very good. That's a telly word. Thank you very much for this conversation. Pleasure.
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