This previously unpublished article relates to my wider interest in the human sense of self and the possibility that we might some day create a sense of self for robots. I have explored this question at length in this book chapter and also in a shorter piece for the New Scientist. This article specifically focuses on the sense of the physical self, that is, awareness of your own body.

---

Why do you feel that your body belongs to you? Perhaps this seems like a surprising question, however, psychologists who study human development, neurologists who investigate the effects of brain trauma, and engineers building robots, have all discovered that have a sense of your own physical body is not a given—it is something you have to work at (at least, your brain works at it, you may not notice). Moreover, having a sense of your physical body, of what is you and what is not you, is a core building block of your wider sense of self and one on which your personal identity, and sense of continuity in time, relies.  In this article I explore what this sense of the physical body is like, how we can flexibly extend it to include tools, cars, even remote robot bodies, and ask whether we could create a similar sense of the physical self for robots.

From body image to body knowledge

The sense of the physical you includes your “body image”, or how you see yourself, and your “body schema”, your experience of your own body and where it is in space. 

The body image is something your mind constructs by looking at or touching your body, or by viewing yourself in a mirror or in pictures. Children below the age of two usually don’t recognise themselves in a mirror indicating that the capacity to form a body image takes some time to develop.  Many animals also fail this mirror test; for instance, a dog will often bark at a mirror, perhaps thinking that it is another dog.  However, there are some animals, other than humans, that do recognize their mirror selves, these include chimpanzees, gorillas, orangutans, and even bottlenosed dolphins. We know this because if you mark their faces with a dab of makeup they will attempt to remove it when they see themselves. So these animals may have a sense of their physical self that may be similar to our own.

Whereas your body image is something you are conscious of, your body schema—your sense and implicit knowledge of where your body is in space—is something that you are much more likely to take for granted. However, your body schema is actually very important for moving around safely and for all sorts of everyday actions, even something as simple as standing up or waving to a friend. Your body schema is created by experiencing the inside of your body, particular the positions of your bones and muscles—what biologists call your proprioceptive sense; and by feeling objects and surfaces, such as clothes, the floor, touch against your skin.

Newborn babies show some abilities to imitate adults suggesting that they already have some elements of a body schema. For instance, if you stick your tongue out at a newborn, even just a few minutes after birth, it might copy you right back! However, babies have only limited abilities to control their bodies, and it takes months for them to master even the seemingly simple challenge of standing on two feet (after all, newborn chicks do this right after they hatch). You might have watched a baby waving its arms and legs in the air, or moving its head around without looking at anything in particular, or staring at its hands. Psychologists believe that all this movement could have an important purpose.  Specifically, in the same way that children “babble” as they are learning to speak, infant movements appear to be a form of “motor babbling” that helps the child find out about its own body.  In other words, moving around, and watching yourself do so, helps you to learn your body schema.

Phantoms and forgetting

As your body grows and changes shape your sense of your physical self adapts without you really noticing.  However, a very sudden change to the body can confuse your brain.  For instance, people who have been unlucky enough to lose a hand or a foot in an accident sometimes report the experience of a “phantom limb“.  In their minds, they feel that the missing limb is still there, they might even feel some phantom sensations in it.  This is because the missing part still exists in their body schema and their brain has not yet caught up with the change. 

A part of the brain called the parietal cortex is important for your sense of physical self.  You’ve probably heard that the left-hand-side of your body is connected to the right-hand-side of your brain and vice versa.  One of the consequences of this is that the body representation in the brain is also split into two halves. People who have suffered brain damage on one side of their brain, for instance through a stroke in one half of the parietal cortex, sometimes lose the ability to think about the opposite side of their body. Losing part of your body image in this way could have the unfortunate consequence that you forget to care for the part that you can’t imagine, so, for instance, you comb your hair but entirely ignore one half of your head.

Losing your sense of the physical body entirely would have a devastating effect on your ability to act in the world. In 1971 Ian Waterman, a 19-year-old butcher from the island of Jersey, contracted a rare viral condition that caused him to entirely lose all proprioception—the sense of where your body and limbs are in space.  Other people who have lost this sense, and there have only been a handful in the world, have been unable to stand, walk, or control their limbs for the rest of their lives. Ian, however, was determined that this wouldn’t happen to him. Gradually, over months and years, Ian learned to control his body again and to successfully co-ordinate the movements of his arms and legs. He did this by consciously and explicitly planning and controlling every action, and by using his eyesight as a replacement for his internal body sense.  Due to his bravery and determination he was able to walk again and to recover the ability to do many things for himself, but he could never recapture the ability to fluidly and automatically control his body in the way that is so natural and effortless to the rest of us. 

Rubber hand—rubber brain

Phantom limb experiences, neglect following stroke, loss of proproception through viral infection, these all show some of limitations of our body’s (and brain’s) ability to respond to sudden traumatic change, however, psychological experiments also show that our physical self is, even so, tremendously adaptable.  For instance, the rubber hand illusion shows that the brain can be fooled into thinking that a hand that looks a bit like your own is part of your body if seeing it is accompanied by the right kinds of sensations. Although we succumb to the illusion, another way to think of this, is as evidence of just how flexible and smart our body schema really is. This flexibility allows us to use tools, to drive cars, even wear robotic exoskeletons. Studies using brain imaging show that we can quickly alter how we represent such objects in our minds to make them a part of our body schema. This allows you to know where the tip of the hammer, or the face of tennis racket, is without having to directly look at it. It is as if the object in your grasp temporarily becomes part of your body.

Body doubles—the new out of body experience

It used to be that only a very small number of people ever had an experience of being outside their own bodies, and this typically happened near the point of death or after meditating in a dark cave for ten years. Now, anyone has the possibility to transport their physical self outside of their biological body through the vehicle of a virtual or robotic body.  This idea has been explored in science fiction movies like The Matrix, Surrogates, and Avatar, but it is not just science fiction—in our new company Cyberselves we are developing technologies that will allow people to “Teleport” into robot bodies in order to perform dangerous jobs or visit friends and colleagues in remote places. Of course, we are all familiar with using remote camera technologies for video chat, but this is different—by directly controlling how the robot moves, and seeing exactly what the robots sees as you turns its/your head, you get a strong feeling of “being there”, or of what researchers in virtual reality call “presence”. A critical factor here, in creating that feeling of inhabiting the robot body, is the tight coupling between action and sensation—as the philosopher Maurice Merleau-Ponty once remarked “my body is wherever there is something to be done”.

Could a robot have a physical self?

Given how important the physical self is to humans and animals, it seems likely that robots would have a use for one too.  Robots will be much safer, for us and them, if they have a sense of their own “bodies” and where they are in space relative to objects and particularly to people. They should also be much better at controlling their movements. Just like human infants, robots are able to learn to control their bodies through motor babbling; that is, by making movements, which could be more-or-less random, and registering their sensory consequences. This has been shown in many robots including a starfish-like robot at Cornell University, the child-like iCub humanoid, and is an important focus for the human brain project.

Giving a robot a sense of its own physical body could allow it to make the self-other distinction and attain a “first person perspective”—a place, behind its camera eyes perhaps, from which it sees the world. This, we can imagine, would be an important first step towards creating the first robot with a true sense of self.