DAVID LIPSON, PRESENTER: Olivia Carter is an associate professor at the University of Melbourne's School of Psychological Services. She previously served as the executive director of the Association of the Scientific Study of Consciousness.

And Jakob Hohwy is a professor from in the Philosophy Department at Monash University. He works on problems in philosophy of the mind, consciousness, neuroscience and mental illness.

They are both appearing at a New Scientist masterclass at UNSW tomorrow and they joined me earlier.

Jakob, Olivia, thanks for joining us on Lateline.

This is a bit of a strange way to start a conversation about consciousness but, Olivia, what don't we know about consciousness?

ASSOC. PROF. OLIVIA CARTER, UNIVERSITY OF MELBOURNE: Yeah, it's a good question. I think as a scientist, it is something that really amazes me, how many people are active in the field and how much we still don't know.

So I think there is a huge variety of different competing theories and probably the one thing that we all agree on is that there is something special about the brain or something about the brain that allows it to be conscious.

Now outside of that, there is so much we don't know. It's really unclear whether it's a specific type of cell in the brain that somehow, when that fires, it magically feels like something to us or is it something about different parts of the brain communicating and when you've got the front and the back working together or something like that, then all of a sudden, magically, you have consciousness.

DAVID LIPSON: Because that's what's extraordinary. You have got a clump of cells that don't know or care who we are, yet you put them together and somehow this magical virtual reality happens.

From a philosopher's point of view, what's your understanding of consciousness?

PROF. JAKOB HOHWY, MONASH UNIVERSITY: I think that scientists delivered a lot of very interesting findings on how brain structure fits with what people report about consciousness but, really, we only have our own consciousness to go by and when I have to assess your consciousness or yours, it's behaviour that's driving it. That's our primary data.

DAVID LIPSON: Because you don't know for sure if I'm conscious?

JAKOB HOHWY: No, you might be a robot, one would hope not.

But within that, that field, there is a lot we know but, at the end of the day, there is a niggling philosophical question. If perhaps we could create a creature, a robot, with exactly the same structure as the human brain, whether that would really be conscious or not and we have no way of knowing and that makes consciousness a rather special type of scientific question.

That's why philosophers are still in on this question as well.

DAVID LIPSON: That's interesting, the AI element of this, Olivia, if we were to create a computer that had the capacity, the speed, everything on paper that a brain can do, is that automatically conscious?

OLIVIA CARTER: So, I mean, that is a question that really splits the field. We don't have an answer to it.

There are a lot of really well-respected academics that would say it's just about the way the information is being processed, it's the computation that the brain is able to compute but once we know the computation, you can replicate that in any system, would by definition be conscious and others say no, it is something special about, I think in the past, people would say it's something special about the human brain.

I think in general, that's no longer a strongly-held view, that probably dog brains, primate brains, maybe down to a fly, can also support consciousness.

DAVID LIPSON: Yeah, right. That would be a different type of consciousness, surely. I suppose every consciousness is different?

OLIVIA CARTER: Exactly. That actually raises a really important question. So you might be more familiar with the idea of how do I know if you're conscious? Well, you might say "I'm going to assume you're conscious and your consciousness is like mine" but what on earth would it be like to be a bee?

DAVID LIPSON: I have heard it described as well, Jakob, as a virtual reality playing out inside your head. Where does that idea come from?

JAKOB HOHWY: It is new theories of how the brain works. We suggest that really the brain harbours this big buzzing model of what the external world is like.

The brain is like a hypothesis tester that constantly tries to infer what things are in the world and then tests that against the sensory input that comes in.

So the idea is that consciousness is harboured in this internal virtual reality which is an interesting view because it kind of detaches us a bit from the world and it might help explain why it is actually so easy for people to fall off the rails, become mentally ill in various ways when this internal model is somehow out of balance.

DAVID LIPSON: I suppose, in terms of that realm of science and mental health and all that sort of thing is the idea of anaesthetic as well. Do we have any understanding, Olivia, of how an anaesthetic erases consciousness?

OLIVIA CARTER: Look, a good understanding, no. The very good at giving the right doses to make sure you're achieving unconsciousness but exactly how that's being achieved is really not understood.

DAVID LIPSON: So it's just been through trial and error and we have become good at it but we don't know what's happening?

OLIVIA CARTER: Exactly, exactly.

DAVID LIPSON: Okay, anything to add to that?

JAKOB HOHWY: As long as people don't wake up and can report what happened. That's success. But whether they were or weren't conscious, that's the issue and we can see these kinds of questions comes up with people in coma and the vegetative state, minimally conscious state, where they've had brain damage.

There is now research that shows perhaps these patients are more conscious than we would judge them to be by their behaviour.

DAVID LIPSON: Then there is the issue of magic tricks, sleight of hand, if you like, and that in many ways is when you start to see cracks appearing in our understanding of consciousness.

That is, we have seen something, we remember it, but it didn't happen. Olivia?

OLIVIA CARTER: Yeah so, I think, one thing that's very, very clear is that our internal experience is not veridical, it is not an internal experience of the external world.

There is, even if we look around and looking at the colours around us in here, we would all be experiencing slightly different intensities, realities, exactly.

We'd be noticing different things and that itself is really interesting.

So the magicians can play on those types of, those tricks.

JAKOB HOHWY: And attention, of course, is a huge factor. The way that attention and consciousness plays in with each other is really important for what you experience right now and magicians are very good at exploiting that and creating those cracks that you talk about.

DAVID LIPSON: What about some of the more whacky, if I could use that expression, theories related to quantum mechanics, Schrodinger's cat, the idea that consciousness determines the very existence around us. That is, that nothing happens in the physical world unless consciousness observes it.

Now I know this isn't sort of directly in the realms of your areas of study but how is that sort of view regarded? Do we have to at least keep an open mind to that?

OLIVIA CARTER: The best way to answer that would be to say that I don't think that many people studying consciousness that would think that the world doesn't exist in the absence of consciousness.

If that's effectively what you're asking?

DAVID LIPSON: But that is the case in terms of quantum mechanics. I mean that very absurdity is now measurable, it is in play, it is in all of our phones, that sort of technology, it's real, so could it apply to the brain?

JAKOB HOHWY: It could and, as you said, there are theories out there that exploit that and I think the best way to look at it is to say there is so little we know about consciousness, that we should have some parcels of research that go on in those more, as you said, whacky areas because why not? Maybe that is where the answer lies but that's a reflection of the immaturity of the scientific field, I think.

DAVID LIPSON: So what about the levels of consciousness in your head? So you mentioned a virtual reality going on, so we are sort of seeing this movie playing on around us with sights, smells, sounds, everything but then you've got the voice in your head as well.

Is that seen as a different part of consciousness or is that sort of commentary to the world that's harping on in the background there?

OLIVIA CARTER: In the scientific field, they call it meta-awareness, awareness of your awareness and there is a sense that it has a different flavour. What that means is there seems to be different, really different aspects of consciousness.

You've got the sensory things, as you said, the voice, the reason, to what extent is that reasonable voice in your head a component of consciousness, or sort of something that, another part of your brain is hearing.

How that interacts is really unclear.

DAVID LIPSON: Do you have, as a philosopher, is there an area that intersects there?

JAKOB HOHWY: It relates to what the self is. The voice that we hear, the commentary, the constant commentary, the stream of thought that we have as we go through our day relates to who you are and consciousness without a self is not really worth having so the question is and that's a philosophical question as well - what is the self?

What is the generator of these thoughts that then leads on to your free action, your sense that you are an agent in the world that can do stuff of your own volition?

So there are really interesting questions underlying that issue about what thought is and how it connects to experience.

DAVID LIPSON: So if we are biological machines, essentially, that are acting in response to stimulus, is there free will? Is that what you are sort of getting at?

JAKOB HOHWY: That's the free will problem. If everything is governed by laws of nature, then how can you insert your free will into it and break that?

And philosophers are good at thinking up sneaky solutions to that, saying "Well, you don't have to be actually free, as long as what you do is in accordance with your beliefs and desires rather than someone else's".

But there is a live debate about that and how that fits in then with the kind of newer science that scientists like Olivia are engaged in.

DAVID LIPSON: Olivia?

OLIVIA CARTER: I was just going to say there is quite a lot of interesting research that shows that if you have a will to move or do something like that, the feeling of having the will to move comes well after the signals in your brain that are clearly driving the action, if that makes sense, so there is...

DAVID LIPSON: There is deception there?

OLIVIA CARTER: There is clearly a deception and whether or not that means you are a victim of your brain's actions or exactly where consciousness fits into that is really unclear but one thing that's interesting is very, very reliably that the sensations of self-generated action come well after.

DAVID LIPSON: That's fascinating.

JAKOB HOHWY: So that relates to the virtual reality. It is almost as if the brain is saying "Given I acted in this way, somehow, I must be free to act" so it creates an internal reality that fits with what happened in the world.

DAVID LIPSON: So you are both experts in your field, where studying what consciousness is, will we ever crack it or is it, by its very nature, impossible to define and understand?

JAKOB HOHWY: A lot of philosophers will give you arguments that says there will always be a core that we can't really get with science but that's not to say we couldn't reveal a hell of a lot about consciousness, the structure and the form, why we have the experiences we have, why the magician is able to deceive you and so on, through science, but a lot of philosophers will say that, at the end of the day, you will never really get rid of the open question about whether the creature that you are studying is genuinely conscious or not. Why is it there in the first place?

DAVID LIPSON: Olivia?

OLIVIA CARTER: So I'm a bit more optimistic. I mean, I find it amazing how much we don't know but the field is moving and I come from the perspective that it is something about our brain and we've got increasing tools to study the brain and I think we will end up with pretty comprehensive answers of why does anaesthesia work in a really detailed way and why does this sort of experience or this sort of brain state generate that sort of experience?

And I think we will have answers. I don't know what it's going to look like but I have quite a lot of confidence, it might be 10, 20 years away, but that we will find an answer.

DAVID LIPSON: I look forward to finding out whether we do or not.

Jakob and Olivia, thanks for joining us on Lateline.