Psychosis: Bending Reality to See Around the Corners | Paul Fletcher | TEDxCambridgeUniversity

Translator: Maria K.
Reviewer: Denise RQ 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? (Laughter) 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) (Laughter) 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 it’s 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) Paul Fletcher: 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. (Applause)


  1. What if your "psychosis" brings a healthy and positive message? I got locked in two different mental hospitals. Both times I had come to realize that I had a bad outlook on life and tried to be more positive. I was taking walks, drinking water, reading philosophy, and writing creatively.
    Psychosis is when my hallucination doesn't match your hallucination. The more common hallucination isn't necessarily the better one.

  2. i wanted to hear about psychosis, but got some freshmen philosophy rant…"all of us have psychosis"… right

  3. One of the few people i have listened to in this world whom doesn't try to impose a false sense of perception in order to receive validation from those around them… I could learn something from this guy

  4. Psychosis is well documented to be caused by lack of sleep, vitamin deficiency's, dehydration, adverse drug reactions to street and prescription drugs, exposure to other toxins, being on a ventilator, being in a hospital (especially for the elderly) and over 100 "medical mimics" (real diseases vrs imaginary "mental illness's" that come part and parcel with "mental/emotional" SYMPTOMS (not diseases in and of them selves) but are highly likely to be misdiagnosed as "MI".

  5. psychosis spiritual awakening; be carefull about what you say and do ie visions precognition, remote viewing and taking to secularist; they will lock you up and fry your brains on drugs!

  6. Thats not Bayes theorem, that is a principle know as "induction", and it has been a subject in philosophy for a couple of thousand of years… He stealing the ideas of philosophy! LOl good video thugh

  7. Psychosis is fun until the Jewish rulers capture you and put you in a mental hospital full of government agents trying to stop the signals from God that reveal the truth about the cycles of the universe and how your going to bring in the end of the world.

  8. You should hear Jordan Peterson's lecture Maps Of Meaning, it's essentially this, it's about the phenomenological perception of the world under constructivist views, which involves left and right cerebral hemispheres and the neuroscience behind them. It is also what the man refers to when he says the expressions "Chaos & Order"… I've personally always thought of it as a radio static signaling through all our receptive senses. immagine the static of a TV. Then imagine that to construct reality and give it a collective meaning that corresponds with our basic survival needs, it has channel itself into something that makes sense to us. It's like turning the radio knob until we hear the music clearly. If you think about it there is a bunch of receptive light and sound spectrum beyond what we can sense, so it's not too off to see things this way.

  9. Had a psychotic episode years ago… had basically delusions. Can only describe it as a illness like in any other organ, where the brain malfunctioned and i was misinterpreting everything with uncontrolled imagination during that time.

  10. Were all psychotic to a certain point because of the artificial environment around us (cities). Our mind is always trying to natirally expand. When we dont undertand this, our minds force the expansion turning the natural experience into something psychotic and chaotic. Most hallucinations are clairvoyancy. Know thy self.

  11. Interesting. But again, the Western scientist refuses to acknowledge that these questions have been pondered upon in India millennia before. Just study Nagarjuna's theory of dependent origination, you'll see exactly the same point, and then some.

  12. I believe the brain in Psychosis creates Alternate Timelines. It creates the illusion of it. Which separates from every other brain.

  13. My psychosis was 7 months long … what the votes did to me is far too much to tell, I spent 10 hours every day bathing for months and this overwhelming being tortured me in every imaginable way. Nobody ever interriert what I've been through … Absolutely nobody .. not my parents, not the doctors and since I'm a loner also no friends … it's been 3 years since I was released from the hospital .. I was 13 months in there and nobody talked to me about my inner world. I become more and more a heartless sick psychopath every day .. I do not know any human I still like .. I hate you all …

  14. Thanks a lot for this wonderful explanation, i experience two years ago a psychotic episode that lasted two and a half months and I'm still trying to understand it fully but the more time passes the more clarity i get on what happened , part of it was definitely from vitamin mineral deficiencies, including especially omega 3s.

  15. "…which hopes to prove that King Tut and Herman Melville influenced each other hardly at all."
    from a letter, circa 1959

  16. The only one that can explain, are the ones that has 1)caused the phenomena or 2)been a victim of it. This is the covering of the mud.

  17. Dont discredit the actual gifted ones with brain disease its unfair. Are you seeing spiders or sharks in thin air? No normal dont.

  18. I too can summarize this in three seconds. "Perceptions aren't reality and neither are words." Thank you very much.

  19. It’s the Medical Field that Doesn’t Understand They Come Up with Terminology when they Don’t UnderStand what’s Causing it and Confuse EveryOne they then Try to Convince you That they’re Right .

  20. In altered consciousness i go to a different place entirely, i see thru the matrix, i see thru the lie that holds the masses in submission, in oppression, in fear and self hatred

  21. The presenter does an excellent job of to some extend normalizing psychotic experiences. I am just concerned that folks who have not experiences tormenting hallucinations — hateful voices that may even tell one to kill himself — would not comprehend how DIFFERENT this "internal model" is, and that it is NOT a voluntary created model…

  22. Watching this here in 2019, and literally within the first 60 seconds I'm 100% certain that Trump suffers from SEVERE psychosis. I guess in the end even if he's done nothing particularly good, his mere existence now proves that psychosis doesn't have to ruin your life, because you can just become President and let it ruin everyone else's lives instead….

  23. When I was psychotic, people started disappearing and also appearing, basically out of nowhere. I also started to have blackouts, moments where I have lost consciousness whilest my body and mind continued to operate. Like if my ability to predict things started to fail. I was not on medication. Also, my sense of time varies.. Now that I am on anti-psychotics, I start to have delusions … So, I might have troubles with the opposite of psychosis…

  24. "Each of us lives within the universe – the prison – of his own brain. Projecting from it are millions of fragile sensory nerve fibers, in groups uniquely adapted to sample the energetic states of the world around us: heat, light, force, and chemical composition. That is all we ever know of it directly; all else is logical inference." (c).

  25. 'A Shamen is someone who swims in thhe same Seaa as thee *Schizophrenic*, but the Shamen hhas Thosands and Thousands of years of sanctioned technique and traditiion to draw upon' – Terrance McKenna

  26. Is the game he's talking about Hellblade: Senua's Sacrifice?

    Also, please fire or re-train whoever edited this.

  27. Because certainty decides reality and only crazy people can control their levels of certainty to collapse quantum superstates decisively.

  28. You cannot understand the future without understanding the past, you cannot understand the past without understanding the future…very mirrored statement; to the extent of being centered.

  29. the problem is that people think that what knowledge they build on is the same for everyones. the truth is that people wire information from the same material differently or only atend to information that may not be the same for everyone. a group of people can be in a room full of animals. after that you can ask them what they remember. some say they remeber the shoes or handbag of some of the other guests. some say that remember a horse, some say they remember a cat. not so many will recall the same things as peoples interest are vastly different, they also wire information off different kind differently. do not assume that the person you are talking to have the same understand of reality as you, as he or she may have wired her learning totally differently from yours.

  30. There is nothing wrong with creating your own explanation for the world. Everyone does it. The problem is that when you're in this kind of states you can't get out. I've had three psychotic episodes. You can't sleep. You can't think rationally to feed yourself. You can't focus and talk to the ones you love that are right next you but you do see them and see the distress you create to yourself and them. You are lost in that world all because it is too satisfying to connect dots as you believe and it doesn't stop until you get medication for it.

  31. I hate when YouTube keeps undoing the likes for videos on me especially when they are this informative

  32. Mental illness doesn't exist…as a free human beings we have all different experiences, so not the same perceptions and subconscious paterns. Who thinks independently and by his own is mentally ill…what a nonsens…like all Psychiatry created to keep us "in line".

  33. just realized he's talking about Hellblade(the video game part). I was curious about psychosis since playing the game and i never would have imagined I'd run into a video with one of the people who collaborated with the creators to make such a haunting experience of a game

  34. Hmm… Slightly concerned by the fact that 'psychosis' is spelt wrong on the powerpoint. But very enjoyable TED talk. 🙂

  35. I suffered delusions and hallucinations. I also suffered from bipolar. The church failed me. They demonized me. I dealt with spiritual abuse. I now have ptsd. I believe in doctors and medications. I thank God for my doctor and medications. I don’t go to church anymore. I’m into new age instead. I meditate a lot and it helps me.

  36. my own problem with the game is that the voices are so articulate whereas psychosis doesn't really give that coherent of a sentence

  37. Unlikely a video game more likely AI iterations. This indicates AI personality engineering. Wow. Reverse engineering the psychiatric science of personality development using disorder models to give rise to AI …ehhm video games. Wow thats some rabbit hole. A man made machine will never have organic psyche.

  38. Hmmm.. Ok, so when evidence backs your perceptions and the results of known input renders an absolute, and repeatable outcome, not just for me but for others I convey to others or they convey to me, isn't reality but psychosis? Sorry, but I trust my perceptions until they don't make sense anymore such as when I've been on pain meds in post surgery. Even then, I knew not to trust my perceptions from the evidence of the events that have happened.

  39. my experiences with psychosis: i was happy in my life living happy like everyone else and i was like completely relax careless person in my 17s and one day suddenly i caught of psychosis . and( it is true when i said this to people they dont believe me . ) after that day my life turned out dark side. i had trouble with people and lost social connections with people . my psychosis is about fear of looking people because i felt like if i look at people i can bother them or they can think bad things about me and this feelings limited my behaviour and i felt like i cant control over my body coz of resisting myself(not on purpose) i felt deep fear feelings that makes me thing if i do wrong thing and whenever i tried not to do some things i found myself doing that more .(my biggest fear is looking people and even if my eyes doesnt stare directly at them i felt like i was looking them)

    if u guys have a same problem u can contact with me.

    comment below

  40. I had accuse physchosis for 6 years. Then it let for about 6 mounts and came back to live with me for two more years. Then it went away and came back for 5 more weeks.
    It totally destroyed my job. I thought I was going to be there President. Then it finally broke again. It was scary

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