Can We Have a Mind Without a Body?

Why can’t you tickle yourself? This glitch points to a surprising connection between your mind and body.

Last week, we had some fun with philosophical zombies—hypothetical creatures that are physically identical to you but lack conscious experience. Essentially, p-zombies are a body without conscious experiences. And we asked whether such a thing might be possible.

This week, we're going to (kind of) flip the question and ask: is it possible to have a mind without a body?

The concept of a mind existing without a body aligns with some forms of functionalism and the currently popular computer metaphor — the mind is software that runs on the hardware of the brain. And it is this software that is important. If we wanted to replicate you, the important thing to replicate would be your mind — the body, it is assumed, is not so important.

But some philosophers and cognitive scientists question this view. They argue that the mind cannot exist without a body — a brain alone is insufficient. The body isn't simply a vehicle for transporting the brain around — it's a necessary part of our thinking, perceiving, and understanding of the world.

This perspective is known as embodied cognition.

So, how essential is the body to the mind?

To find out, we’re asking three questions:

1. What’s the usual way scientists explain what the brain does?

2. What’s wrong with this standard story?

3. Why are bodies important for understanding the world?

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Two caveats before we jump in…

One

It's worth pointing out that those who believe it’s possible that bodies could exist without conscious experiences (like the philosophical zombies) don't necessarily argue that conscious experience could exist without a body. In fact, philosopher David Chalmers, who made the zombie thought experiment popular, has a nuanced view on this matter. More on that in another article.

Two

While it seems like we're flipping last week's question, the issues aren't perfectly symmetrical. Last week, when we discussed philosophical zombies, we asked if a body can exist without conscious experiences. This week, we're exploring something slightly different: minds.

A mind can mean different things to different thinkers. Unlike our previous focus on conscious experience, the mind often encompasses a broader range of mental phenomena. For some, minds are all about conscious experience. For others, it includes a broader range of mental phenomena, which may or may not be consciously experienced.

In this article, let’s focus on one aspect of mental phenomena — sensation and perception. Sensation is detecting things in the world using our senses, like light or sound. Perception is how our brain interprets and makes sense of these sensations, turning them into meaningful experiences.

I’ll discuss the role of the body in other mind activities like thinking, reasoning, and decision-making in an upcoming article on the Brain in a Vat thought experiment.

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Q1: What’s the Usual Way Scientists Explain What the Brain Does?

Most cognitive psychology and cognitive neuroscience researchers are interested in sensation and perception. In other words, most cognitive scientists are interested in how and what information goes into the brain and then what the brain does with that information.

But, of course, sensation and perception are not the only things the brain does.

So, why the focus on sensation and perception?

To answer this question, we need to travel back a little to the late 19th century. During this time, the philosopher William James published The Principles of Psychology. This monumental work spans two volumes and over 1,200 pages. It was an ambitious attempt to summarise all that was known about psychology at the time.

The Principles of Psychology is undoubtedly the most influential work in the history of psychology. It is rare to find a research topic or concept that isn’t covered in its pages. It has shaped, and continues to shape, how cognitive scientists think about the mind and brain, even though it was written over a century ago.

James was an empiricist. He believed that everything we know comes from what we experience through our senses — what we see, hear, touch, smell, and taste. The role of the brain, as James understood it, was to make sense of the information from the senses. It’s not surprising, therefore, that the majority of the 1,200 pages in The Principles of Psychology are dedicated to sensation and perception.

The story that is told (explicitly or implicitly) is that the brain’s main job is to sense and perceive the world — to take in input, evaluate that input, and then decide what to do about it.

The following image shows (in an overly simplified way) the standard story that psychology students are told about how our brain works:

• Step 1: Information from the world enters our brain through our senses and is first processed in areas responsible for processing sensory information.

• Step 2: This information is sent to higher brain areas (often thought to be in the front of the brain), where it forms a mental representation of the world.

• Step 3: In these higher areas, the representation is evaluated, and a decision is made about how to respond.

• Step 4: Once a decision is made, commands are sent to the parts of the brain responsible for movement.

• Step 5: Finally, these motor commands are sent to our body, causing us to act.

This process of taking in input, evaluating it, and then deciding what to do about it — aligns neatly with how we understand what computers do. A computer receives data, processes it, and then produces output. Brains, we are told, are like computers in that they, too, are information-processing systems.

But there’s a big problem with this story.

Q2: What’s Wrong With the Standard Story?

If the brain's main job is to create a representation of the world, we are left with a puzzling question: who is this representation for?

Who or what inside the brain is looking at this representation?

This leads to what philosophers call the homunculus problem -- the idea that there must be a little person (homunculus) inside our head interpreting these representations. It’s the little homunculus who, after watching and interpreting the representations, makes decisions about what to do next.

But then, wouldn't that homunculus need another homunculus inside its head to interpret its representation, and so on and so on, creating something like an infinite set of Russian nesting dolls?

We can probably all agree that there’s no little human inside the head. But without an interpreter of the representation, a representation has no meaning.

In some ways, steps 1 and 2 are similar to the functions of a digital camera. A digital camera reliably represents what it sees when it converts light into digital information. But we aren’t going around saying that cameras find meaning in this digital information. The meaning comes from us, the human viewers, who interpret and understand the images.

So that brings us back to the question — if we are just brains doing something similar to cameras, who or what is the ‘us’ that finds meaning in these representations?

Let’s expand on this conundrum a little further.

Imagine a map that is a representation of a city. For the map to be useful, two things need to happen.

The symbols on the map must match real things in the city — the little building symbol needs to represent an actual building, and the winding blue line needs to stand for a real river. In other words, the map must not be a misrepresentation of the city.

More relevantly, for this analogy, the person using the map needs to understand what these symbols mean. They must know what a building is and that the symbol on the map represents a building. In other words, the map user must connect the map to the real world. Without this connection or grounding, the map is a meaningless piece of paper with drawings.

Let’s apply this idea to our brains. For our brains to create meaningful experiences, sensory inputs need to be grounded in the outside world. In the standard story, the brain forms representations based on sensory input, but representations are not enough to explain how our brain acquires meaning. What's happening in our heads needs to be directly connected — or grounded — to what's happening in the world. Without this grounding, sensory inputs, like undecipherable lines and letters on a piece of paper, are simply abstract signals — with no meaning.

So, how does the brain achieve this grounding? This leads us to question three.

Q3: Why Are Bodies Important For Understanding the World?

What if we’ve been getting it all wrong. What if, the brain’s main job isn’t to create a representation of the world? Instead, what if its primary function is to make the body move and register the consequences of that movement?

We often think that to act on the world we must first perceive the world. But what if we've got it backwards? What if to perceive the world, we must first act?

When babies are first born, their perceptual systems are immature and underdeveloped. But they can move! If you've ever had the privilege of spending time with a baby, you'll know they love to kick.

For many years, we didn't think too much about these seemingly random movements. But recently, developmental psychologists have suggested that kicking is crucial for a baby's brain development. By kicking, the baby learns about its body. Each kick sends valuable information back to the developing brain. This information helps the baby build a map of its body, learning about the basic physics of its body and the environment. The baby doesn't wait for its perceptual system to mature before acting — it acts and, through that action, learns to perceive.

This connection between action and perception isn't only true for babies — it seems to be how our brains work throughout our lives.

Take a look at the following gif. Take 20 seconds to stare at the plus sign and notice what happens to the purple dots.

If you managed to keep your gaze perfectly still on the plus sign, you may have noticed that the purple dots disappear. When you move your eyes, the dots reappear. The purple dots don't actually disappear; your brain simply stops registering them. (By the way, that green dot? — it’s not really there. But I digress).

This phenomenon is known as the Troxler effect. It's an example of how eye movements are crucial for perception. About five times per second, our eyes make a tiny movement. These eye movements are called saccades. And they have the effect of refreshing the visual input coming into our eyes. Without these eye movements, we don't see the dots. Once again, action (moving our eyes) is necessary for this type of perception.

But it's not only our eyes — this principle applies to our entire body. Let's look at one more example that drives this point home.

A few weeks ago, I mentioned the rubber hand illusion — the illusion where people are tricked into feeling sensations in a fake rubber hand. This illusion works because the participant is asked not to move their hand. If they did move their hand, the illusion would immediately break. This is because movement provides feedback that the brain uses to locate and identify our body parts.

The standard story of what the brain does paints the brain as a passive receiver of incoming sensory information. But these examples suggest that we don't simply receive information and then decide what to do about that information. Perception, it seems, is an active process that requires body movements. The standard story of how the brain works, with its neat separation of perception followed by action, may be wrong.

So, if the standard story is not correct, what's really going on in the brain?

To answer this question, we need to talk about something called — efference copy.

Efference Copy

In neuroscience, efference refers to signals sent from the brain to the body (like motor commands), while afference refers to signals sent from the body to the brain (like sensory information). (If you happen to be a student studying this for an exam, just remember E for Exiting the brain and A for Arriving.)

As the name suggests, efference copy is a copy of the efferent signal produced by the motor areas.

When your brain sends a command to move a part of your body (like your eyes), it doesn’t exclusively send the command to the body; it also sends a copy of this command to other parts of the brain, including the sensory areas.

So, the brain’s sensory areas receive two types of information — information in the form of input from outside the brain (from the body and the world) and the efference copy.

So, why would the brain want to send a copy of the motor command to the sensory areas?

The efference copy serves as a prediction of the sensory consequences of our actions. In other words, by sending an efference copy, the brain is able to compare this copy (the prediction) with the actual sensory input it gets from the action your body makes.

This comparison between the efference copy and the actual sensory input is how the brain distinguishes between changes caused by its own actions and those caused by external events.

Let’s use movement as an example. For you to see movement, something must change its position on your retina. This could happen in two ways: when objects in the world move, or when your eyes move. Efference copy is how your brain tells the difference.

When you move your eyes, your brain creates an efference copy of the motor command. Your visual system uses this efference copy to predict how the image on your retina will change due to the eye movement. When you move your eyes, everything in your visual field shifts across your retina, but your brain doesn't interpret this as the world moving — thank goodness. This is because the brain expected this change based on the efference copy.

But if something in your environment moves while your eyes are still, there's no efference copy to predict this change, so your brain interprets it as something in the world moving.

Ever wondered why you can’t tickle yourself? Efference copy explains why. When you attempt to tickle yourself, your brain creates an efference copy of the tickling action. So your somatosensory system has a prediction of the sensation — there’s no surprise. Pretty neat, right? Now you've got at least one answer up your sleeve for that curious six-year-old in your life when they start with the why questions.

The idea that efference copy provides a prediction of sensory outcomes aligns with the predictive processing theory. This theory suggests that the brain constantly generates predictions about incoming sensory information. We briefly reviewed this theory in the article Will AI Ever be Conscious?, but I'll explore these ideas much more in future articles.

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Given all this, some neuroscientists are starting to think we should look at perception differently. They're pushing for what they call an embodied view of perception.

According to this view, creating movement and predicting its effects gives meaning to what we perceive. It grounds incoming sensory information in the world. Without this grounding, input signals would be meaningless.

This perspective challenges the traditional idea of the brain as a passive information receiver and questions the popular computational model of the mind. Instead, it suggests that perception is an active process. We perceive the world because we move.

The embodied view of perception makes us wonder about perception in artificial intelligence and machines. If our perception of the world requires action within that world, how might an AI without a body perceive and understand the world? If an AI could perceive the world without a body, would this challenge the embodied view of perception, or would it suggest biological perception is not the only way to perceive?

This reminds me of the movie Her, where an AI operating system named Samantha seems to perceive and understand the world despite lacking a physical form. For fun next week, let’s discuss the movie Her in the context of perception, consciousness, and disembodied AI.

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