How Science Thinks about Consciousness

Three Empirical Approaches to Understanding Consciousness

Defining consciousness feels like the easiest and the most difficult of tasks.

It feels easy because consciousness seems self-evident. We all know what it's like to be conscious, to experience the world around us, to feel our emotions and think our thoughts. As philosopher Thomas Nagel famously put it, "...the fact that an organism has conscious experience at all means, basically, that there is something it is like to be that organism."

Yet, paradoxically, defining consciousness becomes challenging — sometimes painfully so — when we approach it scientifically or philosophically. Attempts to pin it down often ignite heated debates that frequently end in stalemates.

It doesn’t help that we use the same word to mean different things. We toss all sorts of things into the consciousness bucket! Of course, we throw in our perceptual experiences: sights, sounds, smells, touch and tastes. Then we fling in mental imagery and imagining in too. Bodily feelings like hunger or an itchy nose get lobbed in. Into the bucket goes emotions, memories, wants, and beliefs. Oh! and don't forget that little voice in your head, always chattering away — that goes in as well. And let's not overlook states of consciousness, from meditation and hypnosis to sleep and psychedelic experiences. But we're not done yet! Our bucket also holds the diagnostic use. Is the patient conscious? not conscious? in a coma? And just to make things really messy, we fling big ideas like raising environmental consciousness in too. No wonder our consciousness bucket is hard to make sense of.

When we use the same word to mean several different things, confusion seems inevitable.

So, we should start to unpack what we mean when we talk about consciousness, especially as it is used in the sciences and philosophy.

We’ve been exploring different philosophical perspectives (and will continue to do so). But this week, let's start exploring how science approaches consciousness.

Studying consciousness scientifically is an unusual thing to do. Science likes to study objective, measurable phenomena, and consciousness is (usually considered) subjective. To sidestep this little problem, scientists adopted the pragmatic approach of referring to any scientific study of consciousness as an investigation into the neural correlates of consciousness (or NCCs) rather than simply the scientific study of consciousness. This was a strategic move. It allowed researchers to focus on questions about how consciousness works without getting bogged down in the philosophical debate about what consciousness is.

For this reason, definitions of consciousness in science tend to be operational rather than philosophical. This pragmatic approach has led scientists to separate the study of consciousness into different approaches.

For example, neurologist Antonio Damasio separates consciousness into core consciousness and extended consciousness.

Core consciousness is the type of consciousness we think about when we think about being awake, alert, and aware. This concept aligns closely with what researchers refer to as states of consciousness, which include not just wakefulness but also sleep states, medical states such as coma, altered states induced by meditation or psychoactive substances, and states of sedation or anesthesia.

Extended consciousness is the contents of our conscious experience. This includes all the various contents that make up our experience. So, it includes things like perceptions, thoughts, feelings, memories, bodily sensations, and mental imagery.

Others like to add a third approach — self-consciousness.

There are many ways scientists break down the problem of consciousness, but

1. States of Consciousness

2. Contents of Consciousness, and

3. Self-Consciousness

is a popular breakdown and not a bad place to start.

Let’s take each in turn.

1. States of Consciousness

The idea of states of consciousness is closely tied to the idea of arousal. States of consciousness might include states of wakefulness, sleep and anesthesia. But they also include other states, like meditative states, drug-induced states, or changes in consciousness states due to injury. For example, brain injury can cause coma, unresponsive wakefulness syndrome (formerly known as a persistent vegetative state), minimally conscious state, and locked-in syndrome (the devastating condition of full awareness but with almost complete paralysis).

The brain regions thought to be responsible for our states of consciousness are located in the brainstem, which, evolutionarily speaking, is the oldest part of the brain. The brainstem is primarily responsible for regulating our bodies — so things like breathing and regulating sleep-wake cycles. Damage to this area can lead to coma, unresponsive wakefulness syndrome, locked-in syndrome, or death.

Let's focus on sleep as an example of a different state of consciousness.

In everyday language, there’s a tendency to talk about the awake state as being conscious and the sleep state as unconscious. And in some ways, this makes sense. It is only when we are awake that we can consciously experience our world.

But sleep isn't simply a shutdown — it’s a different state of consciousness.

As our understanding of sleep deepens, we're discovering that even during deep, dreamless sleep, our minds aren't completely switched off. In fact, when people are awakened during the deepest stages of sleep, they often report experiencing mundane thoughts.

Researchers are still trying to figure out what goes on during sleep and how sleep is different to being awake. But one study provides some interesting evidence. Participants’ brain activity was recorded while they were awake and while they were sleeping. The researchers used a technique called transcranial magnetic stimulation (TMS), which sends pulses through the skull to stimulate specific areas of the brain. When participants were awake, the TMS pulse spread across the cortex like ripples in a pond. But during sleep, this pulse did not spread widely. The researchers concluded that during sleep, different parts of the brain might not communicate with each other as much as they do when we're awake.

So, we know that even during dreamless sleep, we still have thoughts (a type of content of consciousness). But the specific contents we can experience seem to depend on our current state of consciousness.

You may have noticed this yourself. If you've ever tried to read during a dream, you've likely found it to be a difficult task. The text does not remain consistent. You might be able to read a word or two but try to re-read the same words, and you’ll notice the words have changed. Coherent reading seems to require an awake state of consciousness.

Did you notice that although we started discussing states of consciousness (e.g., sleep) — we've shifted to discussing the contents of consciousness (e.g., thoughts)? This overlap might be inevitable. We’ll get to why later on.

2. Contents of Consciousness

Contents of consciousness are what we are conscious of.

When we think about it, there is a lot we can be conscious of — from basic sensory experiences like sounds, sights, tastes, touches, and smells to complex internal states such as thoughts, feelings, thoughts about feelings, and feelings about thoughts. Contents can even include more nuanced experiences like a vague sense of déjà vu, the sudden realisation that you forgot to buy milk, or the unexpected urge to organise your sock drawer by colour.

The cortex is thought to be primarily responsible for the contents of consciousness. However, the cortex doesn't work alone. It relies on the brainstem (the brain region responsible for our states of consciousness).

Damasio likens the brainstem to a switch, which determines whether we're conscious at all, while the cortex provides the specific content. Without the brainstem keeping us in an awake, conscious state, the cortex can't produce its awake-like contents.

One way to differentiate states of consciousness from contents of consciousness is to consider individuals who might be missing certain content. For example, a person who is blind no longer has vision as part of their contents of consciousness, but we wouldn't consider them any less awake than someone with normal, healthy vision.

For individuals with degenerative diseases, such as Alzheimer's, the contents of consciousness can change dramatically. As the disease progresses, conscious content becomes more limited and significantly different from their pre-illness state. But while their contents of consciousness are profoundly affected, they continue to expereince states of consciousness, like wake and sleep.

3. Self Consciousness

For most of us, an essential part of experiencing the contents of consciousness is the sense that those contents are experienced by a unified self — an 'I' who does the experiencing.

This sense of self might be responsible for giving us the impression of a unified conscious experience, which is why it's frequently given special status. In psychology and animal cognition research, for example, measures of self-awareness or self-consciousness are often used as indicators of the ‘level of consciousness’.

But many researchers propose that our sense of self is not that special — it’s simply just another content of consciousness.

In fact, anatomically, the sense of self doesn't seem to be a singular thing — it's not localised to a specific region of the brain. It appears that our sense of self is built from many different parts working together. If we lose one of these parts, say through an injury or illness, our sense of who we are can change. The famous case of Phineas Gage is a good example of how the self can dramatically change when brain parts are damaged or missing.

Studies of split-brain patients provide another intriguing example. These patients, who have had the corpus callosum (the main connection between the two brain hemispheres) severed, sometimes display behaviours suggesting two separate selves.

What exactly split-brain patients tell us about our conscious sense of self is still hotly debated. We'll explore the split-brain debate in a future article, but here, I want to raise two other interesting questions.

Does consciousness require a self?

The psychologist Stuart Sutherland argues that,

Many fall into the trap of equating consciousness with self-consciousness — to be conscious it is only necessary to be aware of the external world.

Is Sutherland correct? Does simply being aware suffice for consciousness? Or is there more to it? Does consciousness also require an awareness that we are aware? A meta-awareness?

Ask any long-time meditator, and you’ll receive a resounding — No! Many experienced meditators report states of consciousness without an experiencer, where they have experiences but without the usual sense of being a self.

But this view isn't universally accepted. Some philosophers and cognitive scientists argue that even in these states, there must be some minimal form of self-awareness for the experience to be considered conscious at all.

Does consciousness require content?

At first glance, it might seem obvious that consciousness must always be about something — we're always aware of some sensation, thought, or feeling. This view is known as intentionalism — all mental states are about something.

But is this true?

Is contentless consciousness possible? Can we have a form of consciousness that persists even when all thoughts, perceptions, and emotions — are absent?

Advanced meditative states or psychedelic experiences might have one feeling a sense of ‘nothingness’ or ‘pure being’. Advanced meditators describe such experiences as conscious experiences but without any content.

Critics, however, argue that even these seemingly contentless states must have some minimal content. Perhaps an awareness of time passing or a subtle sense of existing. Maybe what’s being described as contentless is better described as extremely minimal or diffuse content.

The question of whether consciousness requires content has deep implications for answering the philosophical question — what is consciousness?

If we think consciousness always requires content, then we are likely to align our definition of consciousness with intentionalism — consciousness is always about something — or representationalism — conscious experiences represent things in the world or in our minds.

On the other hand, if we think contentless consciousness is possible, we might be more likely to define consciousness as something fundamental — perhaps there is something that underlies all experience that exists even without specific things to be conscious of. This idea might align with certain spiritual traditions and some panpsychist philosophies.

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