an autodidact meets a dilettante…

‘Rise above yourself and grasp the world’ Archimedes – attribution

Posts Tagged ‘consciousness

what is Bayesian inference?

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Canto: So as a dumb non-scientific science aficionado, I’ve come across Bayesian inference and probability a few times before, and even might have come to an understanding of it before losing it again, but I’m wanting to get my head around it, especially in terms of consciousness and how we make sense of the external world via the complex interpreting and understanding systems in our heads. My vague sense of it is that it’s a kind of open-ended system of inferring what’s happening by continually updating the ‘understanding system’ with new data. Is that anything like it?

Jacinta: Okay, we’ve been reading Anil Seth’s Being You, subtitled ‘a new science of consciousness’, which argues for consciousness, or at least perception, as ‘controlled hallucination’. Bayesian reasoning is tightly described as ‘inference to the best explanation’, so yes, we take percepts that strike us as surprising or out of the ordinary, and do work on them through memory or the widening of perspective to make them fit with previous experience – the best explanation we can make of the meaning of that percept. I think by ‘controlled hallucination’, Seth is suggesting that the impressionistic blast of data that impinges on our senses at any moment gets its ‘control’, loses its hallucinatory impact, as a result of what we call experience, the connections between this blast and previous blasts.

Canto: So that due to familiarity we stop thinking of them as blasts, though they might’ve seemed that way as new-borns. And might seem again under the influence of drugs.

Jacinta: Yes, which can scramble the regular controls. But returning to Thomas Bayes and his reasoning, Seth describes it as abductive, as opposed to the deductive reasoning of classical logic, or the inductive reasoning derived from experience (extrapolation from an apparently unending series of observations, such as the regular waxing and waning of the moon). Here’s what Seth says about abduction:

Abductive reasoning – the sort formalised by Bayesian inference – is all about finding the best explanation for a set of observations, when these observations are incomplete, uncertain or otherwise ambiguous. Like inductive reasoning, abductive reasoning can also get things wrong. In seeking the ‘best explanation’, abductive reasoning can be thought of as reasoning backward, from observed effects to their most likely causes, rather than forward, from causes to their effects – as is the case for deduction and induction.

Anil Seth, Being you, p98

Canto: Ah right, so what we experience first are effects – stuff in our heads, and we have to make the best guess about their causes – stuff in the world. Or what we believe to be in the world. So, as new-borns we see – in our heads – the faces and bodies of these people making a fuss over us, though we apparently don’t even know what faces and bodies are, let alone parents. But over time and much repetition we come to see these faces and bodies aren’t there to harm us (if we’re lucky) and, with further information over vast swathes of time, that they’re our parents, and that we’re one of the species called Homo sapiens, etc etc

Jacinta: Well it’s good that you’ve gone back to earliest childhood, because it makes a mockery, in a way, of inferring ‘the most likely cause for the observed data’, to quote Seth, as obviously infants don’t ‘think’ that way.

Canto: And neither do adults – it’s more automatic than ‘thinking’, it’s a way of understanding and surviving in their world…

Jacinta: We need to think of inference as something more basic, far more basic than an intellectual process, of course. Anyway, here’s how Seth describes it. We go from what we already know, which is termed the prior, to what we might know in the future (the posterior) by means of what we’re now learning (the likelihood). The uniting concept here is ‘knowledge’, in its different stages. The prior isn’t necessarily stable, it can be modified or overturned by new learning. You could describe the prior also as a belief. You may believe that, say Ukraine will win the current war – whatever winning means in this context – but further learning may alter that belief one way or another. We’re looking for the best posterior probability, and so, in the Ukrainian example, we’re thoroughly examining future likelihoods – media sources and expert opinions as to the current state of events and what they might lead to – as well as battling with particular tendencies to be optimistic or pessimistic.

Canto: But doesn’t Bayesian inference, or probability, have a mathematical aspect? It doesn’t seem, from what you’ve said, that there’s anything remotely quantifiable here. How can you quantify beliefs or knowledge?

Jacinta: Well, Seth is looking at quantities here only in terms of some percept, say, as being more or less likely to be of a particular thing-in-the-world, say a particular species of bird, based on experience, the likelihood of that species being spotted in that place, at that time, and so on. I know that mathematics is involved in Bayesian probability – just look it up online – but the concept of inferring to the most likely conclusion from best current and past data seems to be mathematical only in that broadest sense. And I must admit I’m more interested in Seth’s concept of consciousness than in the mathematics of probability, Bayesian or otherwise.

Canto: Ah, but I’m wondering if, since all the physicists are telling me the universe is, if not mathematical, inexplicable without mathematics, maybe the full comprehension of consciousness requires maths too?

Jacinta: Okay since our topic is Bayesian inference we might need to wade into the mathematical shallows here. So Thomas Bayes presented an alternative to what is now, and maybe then, called frequentist statistical analysis. Here’s a rough example taken from a video referenced below. A ‘frequentist GP would use basic statistics derived from a model, say ‘a certain number/percentage of my male patients above a particular age have heart problems’ to infer that the patient before her’s symptoms are quite likely the result of a heart condition. A Bayesian GP would have a similar model but would also take into account her prior knowledge of this particular patient, which would make the diagnosis more likely or unlikely depending on the content of this prior knowledge.

Canto: Yeah that’s the mathematical shallows all right.

Jacinta: Well it might surprise you how mathematical even examples like this can be made. But put another way, the Bayesian approach is experiential rather than simple statistical number-crunching. ‘Frequentist’ is given away by the title, so maybe it strives to be objective.

Canto: Quantitative vs qualitative?

Jacinta: Well, yes that’s part of it, but there is a Bayesian theorem, which I may as well stick in here for completeness’ sake.

There are different descriptions of the theorem – this one doesn’t give much indication of the importance of prior knowledge/experience. Anyway, returning to Seth and consciousness, these Bayesian inferences would be constantly updated in the case of infants as you say, as new knowledge is being produced at a rapid clip, that this animal is a dog, say, and is mostly harmless but not always, and this item isn’t food though it’s nice to suck on, but that item tastes horrible – though they wouldn’t know what taste is…

Canto: Which really explains why all these neural connections are laid down do quickly in early childhood – they’re really essential for survival.

Jacinta: And, as Seth points out, the best scientific methods involve Bayesian inference – theories upgraded or discarded by experimental evidence or new discoveries that don’t fit. But our thinking – that, when we’re infants, these people constantly around us are more significant, for us, than the people who pass by or occasionally visit, doesn’t have to rise to the level of theory. They’re just understandings, more or less accurate, and constantly updated – for example we might learn that these adults or pets aren’t always on our side, for example when we try to eat the dog, or whatever. Anyway, we could go into a little bit of detail about the probabilities, from zero to one, of priors, likelihoods and posteriors, and about probability distributions, of the Gaussian kind, which shift as more information comes to mind, but maybe we’ll come back to it in a future post. My head hurts already.

References

Anil Seth, Being you: a new science of consciousness, 2021

Bayesian vs frequentist statistics (video), Ox Educ

Frequentism and Bayesianism: What’s the Big Deal? | SciPy 2014 | Jake VanderPlas (video)

Written by stewart henderson

April 5, 2022 at 4:01 pm

reading matters 9

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New Scientist – the collection: mysteries of the human brain. 2019

  • content hints – history of neurology, Galen, Hippocrates, Descartes, Galvani, Thomas Willis, Emil Du Bois-Reymond, Santiago Ramon y Cajal, connectionism, plasticity, mind-maps, forebrain, midbrain, hindbrain, frontal, parietal and occipital lobes, basal ganglia, thalamus, hypothalamus, amygdala, hippocampus, cerebral cortex, substantia nigra, pons, cerebellum, medulla oblongata, connectome, action potentials, axons and dendritic spines, neurotransmitters, axon terminals, signalling, ion channels and receptors, deep brain stimulation, transcranial direct current stimulation, hyper-connected hubs, 170,000 kilometres of nerve fibres, trains of thought, unbidden thoughts, memory and imagination, the sleeping brain, unconscious activity, the role of dreams, brainwaves during sleep, sleep cycles, traumatic stress disorder, Parkinsons, ADHD, dementia, depression, epilepsy, anaesthesia, attention, working memory, first memories, rationality, consciousness, von Economo neurons, the sense of self…

 

Written by stewart henderson

August 16, 2020 at 3:57 pm

some thoughts on hypnotism

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hmm, are those waves or particles, or both, or neither?

hmm, are those waves or particles, or both, or neither?

Today I want to write about a subject I know bugger all about but which has always fascinated me – hypnotism. The first encounter with it that made an impression on me was as a schoolkid coming home for lunch, as we did every day – our parents were both at work – and catching some of the midday variety show, which regularly featured a bearded and mildly exotic hypnotist who, with nothing more, apparently, than snappings of fingers, intense gazes and a voice of calm command, got ordinary people to crawl on all fours and bark like dogs, or some other form of mild humiliation, to the incredibly complacent amusement of the studio audience – or so it seemed to me.

This was all very flummoxing to my nascent scepticality. Could this really be real? If so, the consequences, it seemed to me, were enormous for a person’s autonomy, or sense of self-ownership. More important, could this ever be done to me? My impulse would be to fight such an outrageous invasion of, indeed takeover of, what I held to be more dear to me than anything else – my independence of thought and action.

So I drew two conclusions from these observations. First, that it couldn’t be real – that there must be at least some fakery involved. Second, that if it was real, I, if not the entire human population, needed to be protected from such outrages, by law. If we could be made to bark like dogs, why couldn’t we be made, by an evil genius, to rip out each others’ throats, to murder our loved ones, to fly planes into buildings or to press nuclear buttons? In fact, if this power to control minds was real, no human law could prevent it from being abused. It followed, according to the Law of Wishful Thinking, that this power couldn’t be real.

But as life went on, the urgency of this issue receded, though the questions raised were never resolved. A lot of nasty things happened, people ripped each other apart, either physically or psychologically, and people murdered those they loved, and flew planes into buildings and declared wars that slaughtered thousands, but the motives seemed all too clear and basic and perennially human. No evil geniuses needed to be posited.  Manipulation might be suspected at times, but of the common and garden type. Hypnosis appeared surplus to requirements, so much that I never really considered it.

The old questions resurfaced on listening to Brian Dunning, of skeptoid.com, presenting a podcast on hypnosis, which provided some interesting historical background, for example that the term ‘hypnosis’ was coined by an English surgeon, James Braid, in the 1840s. Braid became obsessed with the practice after seeing a stage performance, and worked on utilising it for medical purposes. He even wrote a book about hypnotism which, according to Dunning, still stands up well today.

Dunning also addresses an issue that has always vexed me – that of susceptibility to hypnosis. In the 50s, Stanford University developed a rough measure of susceptibility which they named the Stanford Hypnotic Susceptibility Scales. Here’s Dunning’s description:

It’s a series of twelve short tests to gauge just how hypnotized you really are, scored on a scale of 0 (not at all) to 12 (completely). They are responses to simple suggestions like immobilization, simple hallucinations, and amnesia. Most people score somewhere in the middle, and nearly everyone passes at least one of the tests. There’s even a script you can follow to hypnotize anyone and put them through the scales, with a little bit of practice.

Not only do people score very differently, there’s been little progress made in predicting what types of people are most susceptible. Subjects’ suppositions about their own susceptibility don’t correlate at all with test scores. Supposed predictors like intelligence, creativity, desire to become hypnotized, and imaginativeness also have no correlation. Most likely, you yourself are a decent candidate who will score near the middle of the scale, regardless of whether you think you will or not.

These findings are not reassuring. Maybe it’s a male thing (and one of the reasons males are less willing to visit the doctor), but I’ve always wanted to be, and so felt myself to be, ‘in control’ of my physical and mental health. For example, I didn’t need a doctor to tell me I was creeping up in weight towards obesity, with all the attendant health issues. I realised it myself, took control, reduced my general food intake, introduced an exercise regime, and brought my weight back to normal. Similarly, with issues of getting older, such as the possibility of dementia, I reckon that keeping mentally active, learning new things, firing up new pathways, is the self-help solution, and with hypnotism, the defence is a strong mind and a profound unwillingness to be hoodwinked by any evil geniuses out there. But I’m not silly, and I’ve always known that I’m at least partially kidding myself, and that I can’t fully bullet-proof myself against cancer, dementia, or even mind control. So maybe I should subject myself to the above-mentioned susceptibility scales, and face the facts.

For the susceptible ones, there are certainly medical benefits in the application of hypnosis, in relieving stress, in pain management, and in preparing patients for, and managing them through, surgery. Attempts have made to use hypnotherapy, and to analyse its success, in weight loss programs and in treating addictive behaviour, with mixed results.

But what of that worst-case scenario, where the susceptible are manipulated into performing dastardly deeds? Dunning’s conclusions on this seemed reassuring. The susceptible clients certainly reported losing their memory of actions performed under hypnosis, and they certainly did perform those actions, or ‘see’ things they were commanded to see, but, according to Dunning ‘only so long as they were consciously willing to go along.’ He ends with a recommendation to try hypnotism, saying ‘you can’t lose control’ and that ‘you might just have a really wild ride’, two statements that might seem to contradict each other.

But these reassurances were all blown away by Derren Brown’s program on hypnotism, one of a series he presented on how the human mind can be made to believe things and do things that aren’t always in its best interest. Brown is a thorough-going sceptic and an atheist, and so on the side of the angels. I was primed for a dose of debunking, but, frankly, was left with far more questions than answers. I have to rely on my memory here, but the program began with some references to Sirhan Sirhan, the killer of Robert Kennedy in the sixties. Sirhan’s lack of remorse over the years has told against him at parole board hearings and the like, but since he bizarrely claims to have no recollection of the act, his lack of remorse would in that sense be consistent. Without going into too much detail about the assassination (conspiracy theories abound), Brown plants in our minds the germ of an idea that this could’ve been a mind-control event. The rest of the program involves an elaborate set-up in which Brown hypnotises a susceptible subject into ‘killing’ Stephen Fry, with a gun, while Fry is performing onstage, and the hypnotised subject is in the audience. Fry, who’s in on the act, plays dead, and the audience – well, here’s where my memory fails me. I seem to remember shock and confusion, but I don’t recall any heroes grappling with the gunman, or reacting as the gunman stood up and took aim at Fry. Maybe that’s just the behaviour of well-primed security guards. After all, shooting someone when they’re onstage, though theatrical, is hardly a real-life scenario. In fact I don’t recall it ever having happened.

More importantly – in fact far more importantly – the scenario, if we’re to believe it, completely disproves Dunning’s claim that you can’t be persuaded to do something entirely uncharacteristic when under hypnosis. The young man who ‘shoots’ Fry seems to be a pleasant, gentle soul. In an after-event interview with Brown, at which Fry is also present, he has no recollection of firing the gun, though he does remember attending the show (if my memory serves me correctly).

I was really shaken by all this. I tried to wriggle out of the conclusions. Obviously the shooter was using a toy gun – or maybe a real gun with blank bullets. Could it be that he wouldn’t have gone through with it had it been a real gun? That didn’t make sense, really – the gun was in its own case, and looked real enough to me, inexpert though I am (I truly loathe guns). It was no water-pistol or cap-gun. But maybe the whole set-up was a sham? In this and in other Brown shows I found it incredible that subjects could be so easily put into a hypnotised state. In fact ‘ludicrous’ is the word that springs to mind. There’s a part of me – quite a big part in fact – that just wants to dismiss the whole thing as arrant bullshit, a kind of sick joke. How can the human brain, the most complex 1300g entity on the planet, be so easily hijacked?

Well, apparently it can. One has to accept the evidence, however reluctantly. And of course it’s not accurate to say that the entire brain is hijacked. Or rather, just as you don’t have to have complete control of every aspect of a plane in order to hijack it, you just have to control the pilot, so hypnotism must involve control of some kind of consciousness-controller in the brain. Something like what we describe as ‘the self’, no less. A big problem, especially when some psychologists, neurologists and philosophers deny the very existence of the self.

But I’ll leave an exploration of how hypnotism works from a neurophysiological perspective for another post. I suspect, though, that not much progress has been made in that area. Meanwhile, I’m left with a much greater concern about hypnotism than ever before. As if there wasn’t enough to worry about!

Written by stewart henderson

April 20, 2013 at 9:32 am

how to debate William Lane Craig, or not – part 6, intentional states

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mind of god, exclusive pic

mind of god, exclusive pic

Dr Craig’s next argument is that his god is the best explanation of intentional states of consciousness in the world. This is a weird one, and I can only assume that he’s put his best forces in the vanguard in the hope of blowing the opposition out of the water, and that these rather piddling forces in the rear weren’t really meant to be exposed to the light of reason, and were just added to give a scarey sense of bulk or weight to the Doctor’s position. Never mind the quality, feel the width, as they say.

Dr Craig starts by ‘informing’ us that ‘philosophers are puzzled’ by states of intentionality. He doesn’t tell us which philosophers, but the clear intimation is that all philosophers are puzzled in this way – and by the way, this is a very typical piece of deceptiveness from Dr Craig, and your sceptical antennae should be stretched to their outermost limits by offhand remarks such as these. Dr Craig’s presentation here is very thin, but he’s trying, I think to convince you that philosophers are baffled by the non-materiality of intentionality or consciousness generally, and this is a massive misrepresentation of a complex area in the philosophy of mind. It’s true that there’s a lot of interesting debate, and has been for some decades, on the explanation of consciousness in material terms, but there are virtually no philosophers who consider that intentional states are without material cause. That’s to say, that you could have an intentional state without a brain – or something like it, such as a super-computer of some sort. Dr Craig makes the absurd claim that he can think about things, or of things, but a physical object cannot. But I see Dr Craig as a physical object, albeit one with intentions and consciousness. Dr Craig seems to want to make a distinction between objects and conscious subjects, but he doesn’t make this explicit in his rather clumsy argument. I have no difficulty with this distinction, seeing him, as I see myself, and my cat, as both object and conscious subject. In other words I see consciousness as necessarily embodied. Now, what the term ’embodied’ means is really too complex to be gone into here, but I would strongly argue that, while philosophers debate the connection between consciousness and embodiment, and are perhaps especially interested in what embodiment entails, I don’t know of any who are interested in considering consciousness as entirely non-material.

Dr Craig claims that Dr Rosenberg, an atheist, takes the view that ‘there really are no intentional states’, and that ‘we never really think about anything’. I’m not familiar with Dr Rosenberg’s views, but to say that I suspect they’ve been vastly over-simplified and misrepresented by Dr Craig’s characterization of them would be too weak a statement by far. Furthermore Craig claims that Rosenberg’s views, whatever they are, represent atheism. This is nonsense. Philosophers hold vastly different views on the so-called ‘hard problem’ of consciousness, including the view that there is no hard problem. The vast majority of philosophers who debate these issues are, in fact, atheists.

Dr Craig ends this fifth point with another formal argument, which, for the readers’ convenience, I’ll put here.

1. If God did not exist, intentional states of consciousness would not exist.

2. But intentional states of consciousness do exist.

3 Therefore God exists.

However, this argument is so paltry and pathetic that it isn’t worth commenting on further, except perhaps to say that it doesn’t deserve to be called an argument.

Written by stewart henderson

March 19, 2013 at 11:46 pm