Full transcript of neuroscientist Paul Fletcher’s TEDx Talk on Psychosis: Bending Reality to See Around the Corners @ TEDxCambridgeUniversity conference.
Listen to the MP3 audio: Psychosis_ Bending Reality to See Around the Corners by Paul Fletcher @ TEDxCambridgeUniversity
Paul Fletcher – Neuroscientist
I am going to talk about psychosis.
This is an experience or a phenomenon that’s associated with a number of psychiatric, neurological, and physical illnesses. But it’s something more than that, and it’s something that I want to persuade you is actually highly related to the way in which we process the world day-to-day trying to make sense of its complexities.
Psychosis is a much misunderstood, much misused, much criticized term. It’s actually a description, a broad description, not a diagnosis. And it refers to a loss of contact with reality, whatever reality may be.
The textbooks say that there are two key characteristics. The first is hallucinations. People may hear, see, touch, taste, feel things that aren’t apparently there. The other phenomenon is the delusion, a seemingly irrational belief that arises without good evidence.
And it’s held in a way that seems to be impervious to evidence that contradicts it. So that’s the dry textbook definition.
My first experience with psychosis really came when I was a young medical student on my first psychiatry attachment in an inpatient ward in the Hackney Hospital, North East London. And I spent a long time talking to a young man, who described to me in great detail the experience that he’d had of being sent messages from television, film, and radio, and newspapers. Messages in verbal, and visual, and even telepathic forms that were highly critical of him, very unpleasant, very threatening. They even instructed him to harm himself with a knife.
I was deeply disconcerted, but also baffled by this, because he was a young man, who was articulate, intelligent, insightful, and yet, though we seem to inhabit the same world, the reality that he had was very, very different to my own.
And there’s no easy way of applying a simple loss of functional derangement or dysfunction model to understanding that.
Now, I’d like to argue that in order to begin to understand this, to get a glimmer of understanding, we need to take a step back and look at the way that the normal, healthy person in the world processes that world in order to try and make some sense out of its complexities, its ambiguities, and its uncertainties.
And I think through looking at that, we get a glimmer of the possibility that actually, many of us are in a pretty much psychotic state all the time. Primarily, the brain needs to be able to predict the world, to be successful, and to survive.
And in order to do that, it needs to build an internal model of that world outside. And this is where the difficulty starts, because we don’t have direct contact with that world outside.
We have the illusion of direct contact. We have the illusion of reality. This was put very nicely by Vernon Mountcastle, who was a neuroscientist, and he said in 1976, “Each of us lives within the universe or the prison of their own brain. Projecting from it, are millions of fragile sensory nerve fibers, arranged in groups uniquely adapted to sample the energetic states of the world: heat, light, force, chemical composition. That’s all we can know of it directly. Everything else is logical inference.”
Now, this is a profound statement, because it’s telling us that we are actually bringing something to the act of perceiving reality. And it’s worth considering the nature of that inference.
Hermann Von Helmholtz, a 19th century scientist, thought a lot about perception, perceiving and experiencing the world as an inferential, logical process. And in fact, he said that it’s an act of imagination. He said, “Objects are always imagined as being present in the field of vision as would have to be there in order to create the same impression of the nervous mechanism.”
What he was saying here was that we have impressions, experiences on our nervous system just as Mountcastle suggested. And we then have to imagine what could have caused those.
We back project to the cause of the sensations that we do have. This is a form of inference, and it’s a form of inference that this chap here, Charles Peirce, an early 20th century philosopher, referred to as abductive inference or abduction.
Abductive inference really refers to reasoning backwards from evidence to the causes of those evidence. So we have the evidence in our senses, we need to reason backwards. And Peirce pointed out that actually this is one of the shakiest, most fragile, most tenuous forms of logical inference that you could have. He referred to it as guessing.
And the reason is guessing is that for any given sensory experience that we have, there is a myriad, multiple, infinite number of possible causes that could have given rise to that. And we are stuck with having to make a decision about what could have been that cause. As Peirce put it, he said, “The whole fabric of our knowledge is a matted felt of pure hypothesis.”
But we seem to get by. We do manage. And the reason that we manage is actually captured in a theorem that was developed by this 18th century Presbyterian minister Thomas Bayes. Many of you’ll have heard of Bayes’ theorem. You certainly come across it more and more in neuroscience nowadays. And Bayes pointed out, and in fact, Bayes, although he didn’t use the term, was talking about this form of abductive inference, about working out the causes based on the evidence.
And he suggested that the optimal way to do this is to take the evidence but also to take what you already know, what your prior experience and expectation is, and fit those together, and resolve the ambiguity like that.
So imagine you’re walking down a country lane – let’s say, in Devon, and you hear the clip-clop of hoof-taps up around the band. You confidently expect that what will come around the corner next is a horse. But actually the evidence you have doesn’t tell you that necessarily. I mean who can tell the hoof-taps of a horse from a zebra, or a camel, or somebody banging a couple of coconut shells together? The evidence itself is ambiguous.
But of course, it’s your prior knowledge that what’s most likely to be around the corner in Devon is a horse not a zebra. And that’s essentially the insight provided by Bayes’ theorem and the notion of the inference that we apply to the world.
There’s good evidence that this sort of inference also occurs at lower unconscious perceptual levels, and we’re doing it all the time. Looking at this image here, to many of you who haven’t seen what I’ve seen, a meaningless collection of black and white blobs. To me it’s not, to me it’s a very, very meaningful picture.
I can see a lot in it. I can see there’s a woman. I can see that she’s young. I can see she’s wearing a hat. I can see that she’s happy. And I can see that she’s kissing a horse. And the reason I can see all that is not necessarily because I am hallucinating – although there’s an element of that actually, I think – but it’s because I’ve seen this image.
And this image was the original image from which the first one was created. Now, having given you that prior information, that prior expectation, it becomes more possible that some of you may now be able to look at the image and see the woman kissing the horse. This also works in the auditory domain.
If you listen to this… (ambiguous sound) to many of you that will sound like a sort of meaningless bird-songy type of sound. To me actually, it’s highly meaningful. The reason it’s meaningful to me is I have prior expectations and prior knowledge. My prior knowledge comes from having heard this, (voice over) “The camel was kept in a cage at the zoo.” So now you have that prior experience and knowledge.
Will you be able to apply it to the original sound? (Ambiguous sound) It’s very, very striking, just how automatic and easy it is to now make sense of what was previously noise merely because of what you brought to the table. So that’s great.
We’ve got a means of dealing with the world, which allows for the ambiguity of our incoming messages, allows us to assess what the cause is likely to be, by using this inferential process based on prior knowledge. But that should give us pause, because it’s telling this: perception is an active process. It’s not a passive, a receiving of a veridical world out there.
And if the process is active enough to allow us to suppress the noise, recognize the signal, remove the ambiguity, is it also active enough to create perceptions? We are very prone to creating our own perceptions.
So here we see a famous triangle illusion, where most of us will have a very strong sense that there’s a white triangle super-imposed upon these black shapes. The reason we see that probably is because the way the shapes are arranged below it seems to strongly imply that there is a white triangle, and therefore, we create it.
There is actually nothing objectively there. There is no border here. There is no perimeter. We’re seeing something that’s objectively not there. And it’s only 10 minutes ago that I defined that as a hallucination. So this is a hallucination in action. And as Von Helmholtz described it, perception itself is controlled hallucination.
So we have this situation where we have a balance between what’s coming in and what we already know. Under some circumstances, we don’t have any strong expectations, in other circumstances, we have these prior expectations, and we will weigh them.
And this offers us a mechanism for beginning to understand the emergence of phenomena like hallucinations, because it suggests that we don’t need to hypothesize some gross derangement of function, some horrible lesion somewhere. We all define ourselves according to our internal models of the world. We define our place in relation to others, in terms of shared models of the world.
And if somebody’s building a model that isn’t shared by other people, that’s a very, very isolating experience, because their reality becomes different.
Now, I think science can come some way towards trying to look at mechanisms and develop clinical ideas of that, but ultimately, as is encompassed in the theme of today’s talks, really we need to think about experiences like this at other levels.
And that includes – I think very strongly – the arts. My funding body, the Wellcome Trust, are very keen on getting their scientists to work with artists, and they’ve given me a number of fantastic opportunities to discuss these ideas with artists. One example of that was putting me together with a writer, dramatist, and filmmaker, Julian Simpson, who deals a lot of the time with the idea of a brain trying to construct a reality out of sensory inputs.
And a consequence of this discussion and collaboration, although I can’t claim much credit for it at all, was a play that he wrote called “Fugue State,” which actually has already won a few BBC drama awards.
The other collaboration the Wellcome encouraged me with and one I would have never really predicted is with a video game design company, who approached me, because they want to make a video game about an 8th century Celtic warrior who suffers from certain experiences of psychosis.
Well, I was skeptical initially, but having gone to meet them, it actually became very clear to me that they were trying in a very respectful, and sincere, and honest way to try and recapture some of these experiences. So we’ve had a number of meetings where we’ve got together with them and with a wonderful team at Recovery East led by the magnificent Tracy Bartlett, who are a group of individuals who have had experiences of mental illness and who are working towards recovery and are recovered in many cases. They were kind enough, generous enough, and indeed, brave enough to discuss their experiences with the team at Ninja Theory and me.
And a consequence of that is that the game is being developed around these experiences, and Ninja Theory have very kindly given me a clip of film that I just like to leave you with. This is some video from the game itself and some sounds that are really based upon the discussions that we’ve had.
(Video) (Man) Coward
(Woman) They’re coming
(Man) Coward. Coward
(Woman) They’re coming now. They’re coming
(Multiple voices) They’re watching. They’re watching. They’re watching.
[Sometimes the world appears like a kaleidoscope. It can be beautiful.]
(Multiple voices) Out! Get out. Get out. Out! Get out. Get out of here. Get out of here. Get out. Get out of here. Get out. (Video ends)
So this is still very much work in progress, but I hope it leaves you with the impression – which I intend to create – which is talented artists can say more in two minutes about this than I could probably say in an entire series of lectures.
So thank you very much.