How to build a robot that feels
Talk given at CogSys 2010 at ETH Zurich on 27/1/2010
Overview. Consciousness is often considered to have a "hard" part and a not-so-hard part. With the help of work in artificial intelligence and more recently in embodied robotics, there is hope that we shall be able solve the not-so-hard part and make artificial agents that understand their environment, communicate with their friends, and most importantly, have a notion of "self" and "others". But will such agents feel anything? Building the feel into the agent will be the "hard" part.
I shall explain how action provides a solution. Taking the stance that feel is a way of acting in the world provides a way of accounting for what has been considered the mystery of "qualia", namely why they are very difficult to describe to others and even to oneself, why they can nevertheless be compared and contrasted, and, most important, why there is something it's like to experience them: that is, why they have phenomenal "presence".
As an application of this approach to the phenomenal aspect of consciousness, I shall show how it explains why colors are the way they are, that is, why they are experienced as colors rather than say sounds or smells, and why for example the color red looks red to us, rather than looking green, say, or feeling like the sound of a bell.
When Arnold Schwartzenegger, playing the role of a very advanced robot in the film Terminator ends up being consumed in a bath of burning oil and fire, he goes on steadfastly till the last, fighting to protect his human friends. As a very intelligent robot, able to communicate and reason, he knows that what's happening to him is a BAD THING, but he doesnŐt FEEL THE PAIN.
This is the classic view of robots today: people believe that robots could be very sophisticated, able to speak, understand, and even have the notion of "self" and use the word "I" appropriately. But as humans we have difficulty accepting the idea that robots should ever be able to FEEL anything. After all, they are mere MACHINES!
Philosophers also have difficulty with the problem of FEEL, which they often refer to as the problem of QUALIA, that is, the perceived quality of sensory experience, the basic "what it's like" of say, red, or the touch of a feather, or the prick of a pin. Understanding qualia or feel is what the philosopher David Chalmers and what Daniel Dennett call: the "hard problem" of consciousness.
Let's try and look at what is so difficult about understanding feel. The first step would have to be to try to define what we really mean when we talk about feel.
Suppose I look at a red patch of color: I see red. What exactly is this feel of red? What do I experience when I feel the feel of red?
I would say that first of all there are cognitive states : mental associations like roses, ketchup, blood, red traffic lights, and knowledge about how red is related to other colors: for example that it's similar to pink and quite different from green. Other cognitive states are the thoughts and linguistic utterances that seeing redness provoke, as well as the plans, decisions, opinions or desires that seeing redness may give rise to.
Now surely all this can be built into a robot. Perhaps today, not yet in such a sophisticated fashion as with humans. But in the future, since symbolic processing cognitive processing are the very subject matter of Artificial Intelligence, having cognitive states like this is within the realm of robotics. So presumably here there is no logical problem.
Behavioral reactions are a second aspect of what it is like to have a feel. There are automatic reactions like a good driver pressing on the brake at a red traffic light when I drive. There may be physiological tendencies involved in seeing red: perhaps redness changes my general physical state, making me more excited as compared to what happens when I gaze at a cool blue sky.
Both automatic bodily reactions and physiological tendences, to the extent that the robot has a body and can be wired up so as to react appropriately, should not be too difficult to build into the robot. So here too there is no logical problem, although it may take us a few more decades to get that far.
But the trouble is all these components of feel seem to most people not to constitute the RAW feel of red itself. Most people will say that they are CAUSED by the fact that we feel red. They are extra components, products, or add-ons of something that most people think exists, namely the primal, raw feel of red itself, which is at the core of what happens when I look at a red patch of colour.
Does raw feel really exist? Certainly many people would say that we have the impression it exists since otherwise there would be "nothing it's like" to have sensations. We would be mere machines or "zombies", empty vessels making movements and reacting with our outside environments, but there would be no inside "feel" to anything.
Other people, most notably the philosopher Daniel Dennett, considers that raw feel does not exist, and that it is somehow just a confusion in our way of thinking.
But the important point is that EVEN IF DENNETT IS RIGHT, and that raw feel does not really exist, something still needs to be explained. Even Dennett must agree that there is something special about sensory experience that at least MAKES IT SEEM TO MANY PEOPLE like raw feel exists!
Let me look at what this something special is.
Ineffability is really what springs to mind first as being peculiar about feel: namely the fact that because they are essentially first person, ultimately it is impossible to communicate to someone else what feels are like.
I remember as a child asking my mother what a headache was like and never getting a satisfactory answer until the day I actually got one. Many people have asked themselves whether their spouse or companion see colors the same way as they do!
This ineffability has led many people to conclude that an EXTRA THEORETICAL APPARATUS will be needed to solve the problem of the "what-it-is-like" of experience.
This ineffability of raw feels is a first critical aspect of raw feels that we need to explain.
But even if we can't describe feels, there is one thing we know, namely that they are all different from one another.
Sometimes this difference allows for no comparison. Vision and hearing are different. How are they different? Difficult to sayÉ For example there seems to be no basis for comparing the red of red with the sound of a bell. Or the smell of an onion with the touch of a feather. When in this way sensations can't be compared, we say that they belong to different modalities: vision, hearing, touch, smell, taste...
But within sensory modalities, experiences can be compared, or at least structured. Austen Clark in his brilliant book Sensory Qualities looks at this in detail. For example, we can make comparisons on comparisons, and observe that for example red is more different from green than it is from pink.
By compiling such comparisons we can structure sensory qualities and notice that sometimes they can be conveniently organised into dimensions. Dimensions can sometimes be linear going from nothing to infinity as when we go from no brightness to very very bright, or from complete silence to very very loud. Sometimes they go from minus infinity to plus infinity, as from very very cold to very very hot. Sometimes sensations need circular dimensions to describe them adequately, as when we go from red to orange to yellow to green to blue to violet and back to red.
Sometimes, as in the case of smell, as many as 30 separate dimensions seem to be necessary to describe the quality of sensations.
Can such facts be accounted for in terms of neurophysiological mechanisms in the brain?
The simplest example is something like sound intensity. I ask you to reflect on this carefully. If we should find that perceived sound intensity correlates perfectly with neural activation in a particular brain region, with very strong perceived intensity corresponding to very high neural activation. At first this seems like a satisfactory state of affairs, approaching what a neurophysiologist would conceive of as getting very close to an explanation of perceived sound intensity. BUT IT SIMPLY IS NOT!!
For WHY should highly active neurons give you the sensation of a loud sound, whereas little activation corresponds to soft sound?? Neural activation is simply a CODE. Just pointing out that there is something in common between the code and the perceived intensity is not an explanation at all. The code could be exactly the opposite and be a perfectly good code.
Let's take the example of color.
Color scientists since Oswald Hering at the end of the 19th Century have known that an important aspect of the perceptual structure of colors is the fact that their hues can be arranged along two dimensions: a red-green axis and a blue yellow axis. Neurophysiologists have indeed localized neural pathways that seem to correspond to these perceptual axes. The trouble is: what is it about the neurons in the red-green channel that give that red or green feeling, whereas neurons in the blue-yellow channel provide that yellow or blue feeling?
Another issue concerns the perceived proximity of colors and the similarity of corresponding brainstates.
Suppose it turned out that some brainstate produces the raw feel of red and furthermore, that brain states near that state produce feels that are very near to red. This could happen in a lawful way that actually corresponds to people's judgments about the proximity of red to other colors.
The trouble is, what do you mean by saying a brainstate is near another brainstate? Brain states are activities of millions of neurons, and there is no single way of saying this brain state is "more in the direction" of another brain state. Furthermore, even if we do find some way of ordering the brain states so that their similarities correspond to perceptual judgments about similarities between colors, then we can always ask: why is it this way of ordering the brain states, rather than that, which predicts sensory judgments?))
So in summary concerning the structure of feels: this is a second critical aspect of feels we need to explain.
And now for what philosophers consider to be perhaps the most mysterious thing about feels. They "feel like something", rather than feeling like nothing. We all believe that there is "nothing it's like" to a mere machine to capture a video image of red, whereas we really have the impression of seeing redness. Still, though it does somehow ring true to say there is this kind of "presence" to sensory stimulation, the notion is elusive. It would be nice to have an operational definition. Perhaps a way to proceed is by contradiction.
Consider the fact that your brain is continually monitoring the level of oxygen and carbon dioxide in your blood. It is keeping your heartbeat steady and controlling other bodily functions like your liver and kidneys. All these activities involve biological sensors that register the levels of various chemicals in your body. These sensors signal their measurements via neural circuits and are processed by the brain. And yet this neural processing has a very different status than the pain of the needle prick or the redness of the light: Essentially whereas you feel the pain and the redness, you do not feel any of the goings-on that determine internal functions like the oxygen level in your blood. The needle prick and the redness of the light are perceptually present to you, whereas states measured by other sensors in your body also cause brain activity but generate no such sensory presence.
You may not have previously reflected on this difference, but once you do, you realize that there is a profound mystery here. Why should brain processes involved in processing input from certain sensors (namely the eyes, the ears, etc.), give rise to a felt sensation, whereas other brain processes, deriving from other senses (namely those measuring blood oxygen levels etc.) do not give rise to a felt sensation?
But what about thinking or imagining?
Clearly, like the situation for sensory inputs, you are aware of your thoughts, in the sense that you know what you are thinking about or imagining, and you can, to a large degree, control your thoughts. But being aware of something in this sense of "aware" does not imply that that thing has a feel. Indeed I suggest that as concerns what they feel like, thoughts are more like blood oxygen levels than like sensory inputs: thoughts are not associated with any kind of sensory presence. Your thoughts do not present themselves to you as having a particular sensory quality. A thought is a thought, and does not come in different sensory shades in the way that a color does (e.g. red and pink and blue), nor does it come in different intensities like a light or a smell or a touch or a sound might.
To conclude: perhaps a first step toward finding an operational definition of what we mean by "raw feels feel like something" is to note that this statement is being made in contrast with brain processes that govern bodily functions, and in contrast with thoughts or imaginings: neither of these impose themselves on us like sensory feels, which are "real" or "present".
This is mystery number three concerning raw feel.
To summarize then: we have three characteristics of raw feel which are mysterious and seem not to be able to be explained from physico-chemical mechanisms.
This is the hard problem of consciousness.
Under the view that there is something in the brain which generates "feel", we are always led to an infinite regress of questions, and ultimately we are left to invoking some kind of dualistic magic in order to account for the what it's like of feel.
But there is a different view of what feel is which eliminates the infinite regress. This "sensorimotor" view takes the stance that it is an error to think of feels as being the kind of thing that is generated by some physical mechanism, and a fortiori then, it is an error to look in the brain for something that might be generating feel.
Instead the sensorimotor view suggests that we should think of feel in a new way, namely as a way of interacting with the world.
This may not make very much sense at first, so let's take a concrete example, namely the example of softness.
Where is the softness of a sponge generated? If you think about it, you realize that this question is ill posed. The softness of the sponge is surely not the kind of thing that is generated anywhere! Rather, the softness of the sponge is a quality of the way we interact with sponges. When you press on the sponge, it cedes under our pressure. What we mean by softness is that fact.
Note that the quality of softness is not about what we are doing right now with the sponge. It's a fact about the potentialities that our interaction with the sponge present to us. It's something about the various things we could do if we wanted to.
So summarizing about the quality of feels: the sensorimotor view takes the stance that the quality of a feel is constituted by the law of sensorimotor interaction that is being obeyed as we interact with the environment.
But note that something more is needed. It is not sufficient to just be engaged in a sensorimotor interaction with the world for one to be experiencing a feel. We need additionally to be attending, cognitively accessing the fact that we are engaged in this way. I'll be coming back to what this involves at the end of the talk. For the moment I want to concentrate on the quality of the feel, and leave to the side the question of what makes the feel "experienced" by the person.
Let's look at how taking the sensorimotor view explains the three mysteries of feel that I've defined earlier: the ineffability, the structure, and the presence.
Obviously when you squish a sponge there are all sorts of muscles you use and all sorts of things that happen as the sponge squishes under your pressure. It is inconceivable for you to have cognitive access to all these details. It's also a bit like when you execute a practised skiing manoeuver, or when you whistle: you don't really know what you do with your various muslces, you just do the right thing.
The precise laws of the sm interaction are thus ineffable, they are not available to you, nor can you describe them to other people.
Applied to feels in general, we can understand that the ineffability of feels is therefore a natural consequence of thinking about feels in terms of ways of interacting with the environment. Feels are qualities of actually occurring sensorimotor interactions which we are currently engaged in. We do not have cognitive access to each and every aspect of these interactions.
Qualities have structure.
Now let's see how the sponge analogy deals with the second mystery of feel, namely the fact that feels are sometimes comparable and sometimes not, and that when they are comparable, they can sometimes be compared along different kinds of dimensions.
Let's take sponge squishing and whistling as examples.
The first thing to notice is that there is little objectively in common between the modes of interaction constituted by sponge squishing and by whistling.
On the other hand there is clear structure WITHIN the gamut of variations of sponge-squishing: some things are easy to squish, and other things are hard to squish. There is a continuous dimension of softness.
Furthermore, what we mean by softness is the opposite of what we mean by harndess. So one can establish a continuous linear dimension going from very soft to very hard.
So here we have examples that are very reminiscent of what we noticed about raw feels: sometimes comparisons are nonsensical, as between sponge squishing and driving, and sometimes they are possible, with dimensions along which feels can be compared and contrasted.
Whereas we could not explain the differences through physiology, if we reason in terms of sensorimotor laws, these properties of feel fall out naturally.
Let's look at some applications of these ideas to real raw feels.
If I'm right about the qualities of feels, then we can explain why they are the way they are, not in terms of different brain mechanisms that are excited, but in interms of the different laws that govern our interaction with the environment when we have the different feels.
So for example: where lies the difference between hearing and seeing? It does not lie in the fact that vision excites the visual cortex and hearing the auditory cortex.
It lies in the fact that when you see and you blink, there is a big change in sensory input, whereas nothing happens when you are hearing and you blink.
It lies in the fact that when you see and you move forward, there is an expanding flow field on your retinas, whereas the change obeys quite different laws in the auditory nerve.
Now if this is really the explanation for differences in the feel associated with different sensory modalities. Then it makes a prediction: it predicts that you should be able to see, for example, through the auditory or through the tactile modality, providing things are arranged such that the appropriate sensorimotor dependencies are created.
This is the idea of Sensory Substitution. Paul Bach y Rita in the 1970's had already hooked up a video camera worn by a blind person on their spectacles through some electronics to an array of 20 by 20 vibrators that the blind person wore on their stomach or back. He had found that immediately on using the device, observers were able to navigate around the room, and had the impression, of an outside world, rather than feelings of vibration on the skin. With a bit more practice they were able to identify simple objects in the room. There are reports of blind people referring to the experience as "seeing".
With modern electronics, sensory substitution is becoming easier to arrange and a variety of devices are being experimented with.
Bach y Rita and his collaborators have developed a tongue stimulation device which, though it has low resolution, has proven very useful in substitution vestibular information.
There is work being done on Visual to Auditory substitution, where information from a webcam is translated into a kind of "soundscape" that can be used to navigate and identify objects. A link to a movie showing how a subject learns to use such a device is:
There is even an application written in collaboration with Peter Meijer who invented this particular vision-to-sound system that works on some Nokia phones.
Peter Knig and his group at Osnabrck have been experimenting with a belt that provides tactile vibrations corresponding to the direction of north. The device, when worn for several weeks, is, he says, unconsciously made use of in people's navigation behavior, and becomes a kind of 6th sense!
In conclusion on this section concerning the structure of the qualities of feel, we see that the idea that qualities are constituted by the laws of sensorimotor dependency that characterise the associated interactions with the world, is an idea that makes interesting predictions that have been verified as regards sensory substitution.
I now come to another application of the idea, namely to the question of color.
Color is the philosopher's prototype of a sensory quality. In order to test whether the sensorimotor approach has merit, the best way to proceed seemed to us to be to see if we could apply it to color.
At first it seems counterintuitive to imagine that color sensation has something to do with sensorimotor dependencies: after all, the redness of red is apparent even when one stares at a red surface without moving at all. But given the benefit, as regards bridging the explanatory gap, of applying the theory to color, I tried to find a way of conceiving of color in a way that was "sensorimotor".
With my doctoral student David Philipona we realized that this could be done by considering not colored lights, but colored surfaces. Color scientists know that when you take a red surface, say, and you move it around under different lights, the light coming into your eyes can change dramatically. For example in an environment composed mainly of blue light, the reflected light coming off a red surface can only be blue. There is no red light coming off the surface, and yet you see it as red.
The explanation for this surprising fact is well known to color scientists, but not so well known to lay people, who often incorrectly believe that color has something mainly to do with the wavelength of light coming into the eyes. In fact what determines whether a surface appears red is the fact that it absorbs a lot of short wavelength light and reflects a lot of long wavelength light. But the actual amount of short and long wavelength light coming into the eye at any moment will be mainly determined by how much there is in the incoming light, coming from illumination sources.
Thus what really determines perceived color of a surface is the law that links incoming light to outgoing light. Seeing color then, involves the brain figuring out what that law is. The obvious way to do this would be by sampling the actual illumination, sampling the light coming into the eye, and then, based on a comparison of the two, deducing what the law linking the two is.
This is illustrated in this figure. The incoming light is sampled by the three types of photoreceptors in the eye, the L, M and S cones. Their response can be represented as a vector in a three dimensional space. When the incoming light bounces off the surface, the surface absorbs part of it, and reflects the rest. This rest can then be sampled again by the eye's three photoreceptor cone types, giving rise to another three-vector.
It turns out that the transformation of the incoming three vector to the outgoing three vector can be very accurately described by a 3 x 3 matrix. This matrix is a property of the surface, and is the same for all light sources. It constitutes the law that we are looking for, namely the law that describes how incoming light is transformed by this surface.
It is very easy to calculate what the 3 x 3 matrices are for different surfaces. My mathematician David Philipona did this simply by going onto the web and finding databases of measurements of surface reflectivity, databases of light spectra (like sun light, lamp light, neon light, etc.) and figuring out what the matrices were.
Of course human observers, when they judge that a surface is red donŐt do things this way. One way they could do it is to experiment around a little bit, moving the surface around under different lights, and ascertaining what the law is by comparing inputs to outputs. So in that respect the law can be seen as being a sensorimotor law. In many cases however humans donŐt need to move the surface around to establish the law: this is probably because they know more or less already what the incoming illumination is. But in case of doubt, like when you're in a shop under peculiar lighting, it's sometimes necessary to go out of the shop with a clothing article to really know what color it is.
Here are a set of colored chips called Munsell chips which are often used in color experiments. Their reflectance spectra are available for download off the web, and we applied David Philipona's method to calculate the 3 x 3 matrices for all these chips. What did this give? Lots of number, obviously.
But when we looked more closely at the matrices, we discovered something very interesting. Some of the matrices had a special property: they were what is called singular. What this means is that they have the property that instead of taking input three vectors and transforming them into output vectors that are spread all over the three dimensional space of possibilities, these matrices take input three vectors and transform them into a two dimensional or a one dimensional subspace of the possible three dimensional output space. In other words these matrices represent input output laws tht are in some sense simpler than the average run of the mill matrices.
Here is a graph showing the degree of singularity of the matrices corresponding to the different Munsell chips.
You see that there are essentially four peaks to the graph, and they correspond to four Munsell chips, namely those with colors red, yellow green and blue.
And this reminds us of something.
In the 1970's, two anthropologists at Berkeley, Brent Berlin and Paul Kay, studied which colors people in different cultures have names for. They found that there were certain colors that were very frequently given names. Here is the graph showing the number of cultures in the so-called "World Color Survey" which had a name for each of the different Munsell chips.
And here we see something very surprising. The peaks in this graph, derived from anthropological data, correspond very closely to the peeks in the graph I just showed you of the singularity of the Munsell chips.
Here I have superimposed contour plots of the two previous graphs. You see that the peaks of the black contour plots of the singularity data correspond to within one chip of the anthropological data, shown as flat colored areas.
As though those colors which tend to be given names, are precisely those simple colors that project incoming light into smaller dimensional subspace of the three dimensional space of possible lights.
It's worth mentioning that Berlin and Kay, and more recently Kay and Regier have been seeking explanations of their anthropological findings. Though there are some current explanations based on a combination of cultural and perceptual effects, which do a good job of explaining the boundaries between different color names, no one up to now has been able to explain the particular pattern of peaks of naming probabibility, as we have here. And in particular, the red/green and blue/yellow opponent channels proposed on the basis of Hering's findings do not provide an explanation.
On the other hand it does seem reasonable that names should most frequently be given to colors that are simple in the sense that when you move them around under different illuminations, their reflections remain particularly stable compared to other colors.
So in my opinion the finding that we are able to so accurately predict color naming from first principles, using only the idea of the sensorimotor approach, is a great victory for this approach.
There is another quite independent victory of the sensorimotor approach to color that concerns what are called unique hues. These are colors that are judged by people to be pure, in the sense that they contain no other colors. There is pure red, green, yellow and blue, and people have measured the wavelengths of monochromatic light which provide such pure sensations.
Unfortunately, the data are curiously variable, and seem to have been changing gradually over the last 50 years. Furthermore, the data have not been explained from neurophysiological red/green and yellow/blue opponent channels.
The dots in this graph show empirical data on channel activations observed to obtain unique red, yellow, green and blue. Instead of crossing at right angles, the data are somewhat skewed.
What this means is that, for example, in order to get the sensation of absolutely pure red, you cannot just have the red channel that is maximally active. You have to have a little bit of activation also in the yellow channel.
Similarly, to get unique blue, you need not just activation in the blue channel, but also some activation in the green channel.
On the other hand it is easy, on the basis of the matrices that we have calculated for colored chips, to make predictions about what people will judge to be pure lights. And these predictions turn out to be right spot on the empirical data on observed unique hues. In fact the black lines in the graph are the predictions from the sensorimotor approach.
Another fact about unique hues is their variability. The small colored triangles on the edge of the diagram here on the right shows the wavelengths measured in a dozen or so different studies to correspond to unique red, yellow, blue and green. You see the data are quite variable. The colored lines are the predictions of variability proposed by the sensorimotor approach. Again, the agreement is striking.
Incidentally we can also account for the fact that the data on unique hues has been changing over recent years. We attribute this to the idea that in order to make the passage from surfaces to lights, people must have an idea of what they call natural white light. And this may have been changing because of the transition from incandescent lighting to neon lighting used more often today.
As a final point about color and the sensorimotor approach, I'd like to mention some experiments being done by my ex PhD student Aline Bompas. Here she is wearing what looks like trendy psychedelic spectacles.
The effect of these spectacles is to make it so that when she looks to the right, everything is tinged with yellow, and when she looks to the left, everything is tinged with blue. Now under the sensorimotor theory, this is a sensorimotor dependency which the brain should learn and grow accustomed to. After a while, we predict, people wearing such spectacles should come to no longer see the color changes. Furthemore, once people are adapted, if they then take off the spectacles, they should then see things tinged the opposite way. For example if they look at a grey spot on a computer screen, when they turn their head one way or the other they should have to adjust the spot to be more yellowish or more blueish for it to appear grey. And this should happen, despite the fact that they are not wearing any spectacles at all.
Aline Bompas has been doing interesting experiments which do indeed confirm this kind of predictions.
Another application of the sensorimotor approach to the qualities of sensation concerns body sensation.
Why is it that when I touch you on the arm, you feel it on your arm? You might think that the answer has something to do with the fact that sensory stimulation is relayed up into the brain into a somatosensory map in parietal cortex, where different body parts are represented, as in the well-known Penfield homunculus.
But the fact is that this doesnŐt explain anything. The fact that a certain brain area represents a certain body part doesnŐt explain what it is about that brain area which gives you sensation in that particular body part. What is it about the arm location in the somatosensory map which gives you that "arm" feeling rather than, say, the foot feeling, or any other feeling?
The sensorimotor approach claims on the contrary that what constitutes the feel of touch on the arm is a set of potential changes that could occur: the fact that when you move your arm when your arm is being touched, it changes the incoming tactile stimulation, whereas when you move, say your foot when you're being touched on your arm doesnŐt change anything. The fact that when you look at your arm when you're being touched on your arm, you're likely to see something touching it, whereas if you look, say, at your foot, you're not likely to see anything touching it.
What constitutes that arm-feel is the set of all such potential sensorimotor dependencies.
Now if this is true, it makes an interesting prediction. It predicts that if we were to change the systematic dependencies, then we should be able to change the associated feel. This is exactly what is done in the Rubber Hand Illusion.
In the RHI a person watches a rubber hand being stroked while at the same time their own real hand is stroked simultaneously. Most people after a few minutes get the peculiar impression that the rubber hand belongs to them. This is measured by a questionnaire and by a behavioural response, which is to indicate the felt position of the index finger.
This result is very much in keeping with the predictions of the sensorimotor approach. With my student Camila Valenzuela-Moguillansky we are working on this phenomenon, in particular with regard to pain. As shown in the lower figure, if we simultaneously stimulate the real hand and the rubber hand with a painful heat stimulus, when people have transferred ownership of their hand to the rubber hand, they feel less pain in the real hand.
It's also possible to use different size rubber hands, as here, and give people the impression that their real hands are bigger or smaller than they really are.
Yet another application of the sensorimotor approach I would like to mention concerns the perception of space. In this work, done with mathematician student David Philipona, we showed how it's possible for a brain to deduce the algebraic group structure of three dimensional space by looking at the sensorimotor laws linking sensory input to motor output. We did this for the case of a simulated rat, which had eyes and head that moved, pupils that contracted. The sensory input was multimodal and came from vision, audition and from tactile input from the whiskers. We have been looking further into how this approach might help in robotics for multimodal sensory fusion and calibration.
Up to now I've looked at how the sensorimotor approach can deal with the ineffability and the structure of the qualities of feel.
Now let's look at the third mystery of feel, the question of presence i.e. of why people say "there's something it's like" to have a feel.
I had already mentioned the difficulty of really understanding what it means to say that there's something it's like to feel, and that to solve this problem we might use an operational definition and proceed by contradiction. This could consist in noting that there are some processes in the brain and nervous system like automatic functions, on the one hand, and thoughts on the other hand, which presumably do not possess the mysterious "something it's like".
The difficulty with the traditional way of thinking about feel as being generated by the brain is that there seems to be no way we could conceive of why autonomic and thought mechanisms could generate no feel, whereas sensory mechanisms would.
Under the sensorimotor view, on the other hand, we are no longer searching for physical mechanisms which generate feel. So instead of searching for physical or physiological mechanisms that do or do not generate the "something it's like", we can search for characteristics of our interaction with the environment of which one could say that they correspond to the notion of feeling like something.
If you ask yourself, let's say in the case of feeling the softness of a sponge why there's something it's like to do this, I think you come to the conclusion that the reason there's something it's like is pretty obvious: you really are doing something, not just thinking about itÉ or letting your brain deal with it automatically.
But then what is it about a real interaction with the world that allows you to know that it you really are having such a real interaction? How do you know, when you're squishing a sponge, that you REALLY ARE squishing it, and not just thinking about it, hallucinating or dreaming about it?
The answer I think lies with four aspects of real-world interactions which are: Richness, bodiliness, insubordinateness and grabbiness.
First of all, the world is rich in details. There is so much information in the world that you cannot possibly imagine it. If you're just thinking about squishing a sponge, you cannot imagine all the different possible things that might happen when you press here or there. If you're imagining a visual scene, you need to rely on your own inventivity to imagine all the details. But if you really are looking at a scene, then wherever you look, the world provides infinite detail.
So richness is a first characteristic of real-world interactions that distinguishes them from imagining or thinking about them.
Bodiliness is the fact that voluntary motions of your body systematically affect sensory input. This is an aspect of sensory interactions which distinguishes them from autonomic processes in the nervous system and from thoughts.
Sensory input deriving from visceral autonomic pathways is not generally affected by your voluntary actions. Your digestion, your heartbeat, the glucose in your blood, although they do depend somewhat on your movements, are not as intimately linked to them as your sensory input from your visual, auditory and tactile senses. If you are looking at a red patch and you move your eyes, etc., then the sensory input changes dramatically. If you are listening to a sound, any small movement of your head immediately changes the sensory input to your ears in a systematic and lawful way. If you're thinking about a red patch of color or about listening to a sound, then moving your eyes, your head, your body, does not alter the thought.
Note that the idea that bodiliness should be a test of real sensory interactions is related to the fact that people often say that a way of testing whether you are dreaming is to make a voluntary action that has an effect on the environment, like switching on a light.
But note now the interesting case of proprioception. Here is a case where we definitely have bodiliness, since voluntary limb movements do systematically affect incoming proprioception. On the other hand, I don't think proprioception really is felt in the same way that other sensory feels are felt.
Bodiliness by itself seems therefore not to be a guarantee that a sensation will be felt.
Indeed the reason bodiliness is not a perfect guarantee of a sensation being real is that for it to be real, bodiliness must actually be incomplete. This is because what characterises sensations coming from the world is the fact that precisely they are not completely determined by our body motions. The world has a life of its own, and things may happen: mice may move, bells may ring, without us doing anything to cause this. I call this insubordinateness. The world partially escapes our control.
And then there is grabbiness. This is the fact that sensory systems in humans and animals are hard-wired in such a way as to peremptorily interfere with cognitive processing. What I mean is that when there is a sudden flash or loud noise, we react, automatically by orienting our attention towards the source of interruption. This fact is an objective fact about the way some of our sensors -- namely precisely those that we say we feel, are wired up. Visual, auditory, tactile olfactory and gustatory systems possess sudden change (or "transient"-) detectors that are able to interrupt my ongoing cognitive activities and cause an automatic orienting response. On the other hand a sudden change in my blood sugar or in other autonomic pathways like a sudden vestibular or proprioceptive change, will not cause exogenous orienting. Of course such changes may make me fall over, or become weak, for example, but they do not directly prevent my cognitive processing from going on more or less as normal -- although there may be indirect effects of course through the fact that I fall over or become weak.
My idea is that what we call our real sense modalities are precisely those that are genetically hard wired with transient detectors, so as to be able, in cases of sudden change, to interrupt our normal cognitive functioning and cause us to orient towards the change. Those other, visceral, autonomic sensing pathways, are not wired up this way. It is as though normal sense modalities can cause something like a cognitive "interrupt", whereas other sensing in the nervous system cannot.
Note that grabbiness allows us also to understand why thoughts are not perceived as real sensations. If you are seeing or hearing something, any change in the environment immediately creates a signal in the transient detectors and alerts you that something has happened. But imagine that overnight neurons die in your brain that code the third person of the latin verb "amo". Nothing wakes you up to tell you this has happened. To know it, you have to actually think about whether you still remember the third person of amo. In general, except in the case of obsessions, thoughts and memory do not by themselves interrupt your cognitive processing in the way that loud noises and sudden flashes or pungent smells cause automatic orienting.
Grabbiness is particularly important in providing sensory feel with its "presence" or "what it's like". I would like to illustrate this with the example of seeing.
When we see a visual scene, we have the impression of seeing everything, simultaneously, continuously, and in all its rich, detailed splendor. The visual scene imposes itself upon us as being "present". Part of this presence comes from the richness, bodiliness and insubordinateness provided by vision. The outside world is very detailed, much more so than any imaginable scene. It has bodiliness because whenever we move our eyes or body, the input to our eyes changes drastically. And it is insubordinate because our own movements are not the only thing that can cause changes in input: all sorts of external changes can also happen.
But there is also grabbiness. Usually, if something suddenly changes in the visual scene, because transient detectors in the visual scene automatically register it and orient your attention to it, you see the change, as in this movie:
But if you make the change so slow that the transient detectors donŐt work, then an enormous change can happen in a scene without your attention being drawn to it, like in this movie:
Where almost a third of the picture changes without you noticing it.
Another way of preventing transient detectors from functioning normally is to flood them with additional transients, like here where the many white "mudsplashes" prevent you noticing the transient which corresponds to an important picture change.
These 'slow change' and mudsplash demonstrations are part of a whole literature on "change blindness". Change blindness can also occur if the interruption between scenes that causes the transients to be drowned out is caused by flicker in the image, or by eye saccades, blinks, or film cuts, or even by real life interruptions.
So to summarize up to now:
I have shown how the new view of feel as a sensorimotor interaction with the environment can explain the three mysteries of feel: its ineffability, the structure of its qualities, its presence. These are all explicable in terms of objective aspects of the sensorimotor laws that are involved when we engage in a sensorimotor interaction with the environment.
But these are all aspects of the QUALITY of feel. You may note that I have not at all talked about how when you have a feel É
you can have the impression of consciously experiencing that feel??
But I think this poses no theoretical problem. I would like to claim that what we mean by consciously experiencing a feel is: cognitively accessing the quality of the sensorimotor interaction we are currently engaged in.
As an example, take the opposite case:
Take driving down the highway as you think of something else. When you do this you would not say you are in the process of experiencing the driving feeling.
For you to actually experience something you have to be concentrating your attention on it, you have to be cognitively engaging in the fact that you are exercising the particular sensorimotor interaction involved.
Illustrations of the role of attention in perception are well known in psychology.
One very impressive, practical application of this is in the domain of traffic safety. There is a phenomenon known to researchers studying road accidents called "LBFTS": "Looked but failed to see". It turns out that LBFTS is the second most frequent cause of road accidents after drunken driving. The phenomenon consists in the fact that the driver is looking straight at something, but for some reason doesn't see it.
Particularly striking cases of this occur at railway crossings. You might think that the most frequent accident at a railway crossing would be the driver trying to get across the track quickly right before the trian comes through. But in fact it's found that the most frequent cause of accidents at railway crossings is exactly the opposite: the train is rolling quietly across the crossing and a driver comes up and, although he is presumably looking straight ahead of him at the moving train, simply doesnŐt see it, and crashes directly into it. If you do a search on the net for "car strikes train" you'll find hundreds of examples in local newspapers like this one.
This shows that what you look at does not determine what you see. Here's another example: you may think it says here "The illusion of seeing". Look again.
There are actually two "of"'s. Sometimes people take minutes before they discover this.
The reason is that seeing is not : passively receiving information on your retina. It is: interrogating what's on your retina and making use of it. If your interrogation assumes there's only one word "of", then you simply donŐt see that there are two.
If you're driving across the railway crossing, even though your eyes are on the train, if you're thinking about something different, you simply donŐt see the train, and É bang.
Psychologies are of course very interested in attention, and do interesting experiments to test your ability to put your attention on something when all sorts of other things are going on in the visual field.
Here's an example made by my ex student Malika Auvray, where you have to follow the coin under the cup. It's a bit tricky because there are lots of hands and cups all moving around: so concentrate!
At the end of the sequence : did you see anything bizarre?
It was the green pepper replacing one of the cups. Many people donŐt notice this at all, presumably because they're busy following the coin. And this is despite the fact that the green pepper is in full view and perfectly obvious.
The demo I just showed is a poor version of a truly wonderful demo made by Dan Simons, where a gorilla walks through a group of people playing a ball game, and where you simply donŐt see the gorilla even though it's in full view.
Transport for London has a reworked version of this that they use as an advertisement for people to drive carefully, and you can find it on youtube:
So in conclusion up to now:
Consciously experiencing a feel requires you first to be engaged in the skill implied by that feel. If the skill has the properties that sensory feel have, that is, if it has richness, bodiliness, insubordinateness and grabbiness, then the quality it will have the sensory presence or "what it's like" that real sensory feels possess.
If then you are attending, or cognitively accessing the feel, you will be conscious that you are doing so.
But wait, there's a problem: who is "you"?!
It doesn't make much sense to say that a person or an agent is consciously experiencing the feel, unless the person or agent exists as a person, that is unless the agent has what we call a SELF.
Is this a problem for science? Philosophers have looked carefully at the problem posed by the notion of self and come to the conclusion that though the problem is tricky, it is not a "hard" problem in the same sense as the problem of feel was.
One aspect of the self is what could be called the cognitive self, which involves a hierarchy of cognitive capacities.
At the simplest level is "self-distinguishing", that is the ability for a system or organism to distinguish its body from the outside world and from the bodies of other systems or organisms.
The next level is "self-knowledge". Self knowledge in the very limited sense I mean here is something a bird or mouse displays as it goes about its daily activities. The animal exhibits cognitive capacities like purposive behavior, planning, and even a degree of reasoning. To do this its brain must distinguish its body from the world, and from other individuals. On the other hand the bird or mouse as an individual presumably has no concept of the fact that it is doing these things, nor that it even exists as an individual.
Such knowledge of self-knowledge is situated at the next level of my classification. Knowledge of self-knowledge can lead to subtle strategies that an individual can employ to mislead another individual, strategies that really are seen only in primates.
Knowledge of self-knowledge is most typically human, and may have something to do with language. It underlies what philosopher Daniel Dennett calls the "intentional stance" that humans adopt in their interactions with other humans. The individual can have a "Theory of Mind", that is, it can empathize with others, and interpret other individuals' acts in terms of beliefs, desires and motivations. This gives rise to finely graded social interactions ranging from selfishness to cooperation and involving notions like shame, embarrassment, pride, and contempt.
I have called all these forms of the cognitive self "cognitive" because they involve computations that seem to be within the realm of symbol and concept manipulation.
There seems to be no conceptual difficulty involved in building these capacities into a robot. It may be difficult today ((-- particularly as we don't know too well how to make devices that can abstract concepts. Furthermore we don't currently have many robot societies where high level meta knowledge of this kind would be useful. ))
But ultimately I think the consensus is that there is no logical obstruction ahead of us.
So I think we can say that the cognitive self isÉ
Accessible to a robot
On the other hand there does still seem to be something missing. We as humans have the strong impression that there is someone, namely ourselves, "behind the commands". ((We are not just automata milling around doing intelligent things: there is a pilot in the system, so to speak, and that pilot is "I".))
It is I doing the thinking, acting, deciding and feeling. How can the self seem so real to us, and who or what is the "I" that has this impression?
And here I want to appeal to current research in social and developmental psychology. Scientists in these fields agree that although we have the intimate conviction that we are an individual with a single unified self, the self is actually a construction with different, more or less compatible facets that each of us gradually builds as we grow up.
The idea is that the self is a useful abstraction that our brains use to describe, first to others and then later to ourselves, the mental states that "we" as individual entities in a social context have. It is what Dennett has called a narrative fiction.
But then how can the self seem to us to be so real? The reason is that seeming real is part of the narration that has been constructed. The cognitive construction our brains have developed is a self-validating construction whose primal characteristic is precisely that we should be individually and socially convinced that it is real.
It's a bit like money: money is only bits of metal or paper. It seems real to us because we are all convinced that it should be real. By virtue of that self-validating fact, money actually becomes very real: indeed, society in its current form would fall apart without it.
The self is actually even more real than money because it has the additional property that it is self-referring: like some contemporary novels, the "I" in the story is a fiction the "I" is creating about itself.
In which case, shouldn't we be able to change the story in mid course? If our selves are really just "narrative fictions" then we would expect them to be fairly easy to change, and by ourselves furthermore!
But actually this does not work. It is necessarily part of the very construction of the social notion of self, that we must be convinced that it is very difficult to change our selves. After all, society would fall apart if people could change their personalities from moment to moment.
But couldn't we by force of will just mentally overcome this taboo? If the self is really just a story, changing the self should surely in fact be very easy.
It turns out that we can under some circumstances break the taboo ((of thinking that our selves are impossible to change,))
and flip into altered states where we become different, or even someone else. Such states can be obtained voluntarily through a variety of Ňculturally boundÓ techniques like possession trances among others ((, ecstasies, channeling provoked in religious cults, oracles, witchcraft, shamanism, or other mystical experiences. Latah, amok, koro)) and hypnosis;
or sometimes involuntarily under strong psychological stress ((physical abuse, brainwashing by sects, in religious cults and in war -- Post traumatic stress disorder, Dissociative Identity disorderÉ)).
Hypnosis is interesting because it is so easy to induce, confirming the idea that the self is a story we can easily control if we could only decide to break the taboo. Basic texts on hypnosis generally provide an induction technique that can be used by a complete novice to hypnotize someone else. This suggests that submitting to hypnosis is a matter of choosing to play out a role that society has familiarized us with, namely "the role of being hypnotised". It is a culturally accepted loophole in the taboo, a loophole which allows people to explore a different story of "I". An indication that it is truly cultural is that hypnosis only works in societies where the notion is known. You can't hypnotise people unless they've heard of hypnosis.
This is not to say that the hypnotic state is a pretense. On the contrary, it is a convincing story to the hypnotized subject, just as convincing as the normal story of ŇIÓ. So convincing, in fact, that clinicians are using it more and more in their practices, for example in complementing or replacing anesthesia in painful surgical operations.
There is also the fascinating case of Dissociative Identity Disorder (formerly called Multiple Personality Disorder). A person with Dissociative Identity Disorder may hear the voices of different ŇaltersÓ, and may flip from ŇbeingÓ one or other of these people at any moment.
The different alters may or may not know of each othersŐ existence. The surprising rise in incidence of Dissociative Identity Disorder /MPD over the past decades signals that it is indeed a cultural phenomenon. Under the view I am taking here, Dissociative Identity Disorder /MPD is a case where an individual resorts to a culturally accepted ploy of splitting their identity in order to cope with extreme psychological stress. Each of these identities is as real as the other and as real as a normal personŐs identity – since all are stories.
In summary, the rather troubling idea that the sense of self is a social construction seems actually to be the mainstream view of the self in social psychology.
If this view is correct, then we can confirm that there really is logically no obstacle to us understanding the emergence of the self in brains. Like the cognitive aspect of the self, the sense of "I" is a kind of abstraction that we can envisage would emerge once a system has sufficient cognitive capacities and was immersed in a society where such a notion would be useful. The self is:
Accessible to a robot
So we can now finally come to the conclusion. The idea is that I have a conscious phenomenal experience when this social construct of "I" engages cognitively in the exercise of a skill. If the skill is a purely mental skill like thinking or remembering it will have no sensory quality. But if it involves a sensorimotor interaction with the environment, then it will have richness, bodiliness, insubordinateness, and grabbiness. In that case it will have the "presence" or "what it is likeness" of a sensory experience.
Notice that there are two different mechanisms involved here. The outside part, the knowing part is a cognitive thing, it involves cognitive processing, paying attention. There is nothing magical about this however, it is simply a mechanism that brings cognitive processing to bear on something so that that thing becomes available to one's rational activities, to one's abilities to make decisions, judgments, possibly linguistic utterances about something. It is perhaps what Ned Block calls access consciousness.
The inside part is the skill involved in a particular experience. It is something that you do. Your brain knows how to do it, and has mastery of the skill in the sense that it is tuned to the possible things that might happen when it ...
The outside, cognitive part determines WHETHER you sense the experience.
The inside, skill part, determines WHAT the experience is like.
In summary, the standard view of what experience is supposes that it is the brain that creates feel. This standard view leads to the "hard" problem of explaining how physico-chemical mechanisms in the brain might generate something psychological, out of the realm of physics and chemistry. This explanatory gap arises because the language of physics and chemistry is incommensurable with the language of psychology.
The sensorimotor view overcomes this problem by conceiving of feel as a way of interacting with the environment. The quality of feel is simply an objective quality of this way of interacting. The language with which we describe such laws objectively and the language we use to describe our feels are commensurable, because they are the same language. What we mean when we say there is something it's like to have a feel, can be expressed in the objective terms of richness, bodiliness, insubordinateness and grabbiness. What we mean when we say we feel softness or redness can be expressed in terms of the objective properties of the sensorimotor interaction we engage in when we feel softness or redness.
For further information, here is the address of my web site.