How we build perception from the inside out
Seth (Anil Kumar)
Source: Aeon, 30 June, 2020
Paper - Abstract

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Editors' Abstract


Rough Transcript & Notes2
  1. (0:00): Talking about conscious experience. What does Seth mean by “conscious”? Difficult to provide an agreed scientific definition. But everyone knows it’s what we lose in a dreamless sleep or under anesthesia and regain when we wake up. Any kind of subjective experience (including thinking). For a conscious organism there is “something it is like to be that organism”. There’s nothing it’s like to be a chair “let’s suppose”; but a person, monkey, octopus … maybe a honeybee … this is something it’s like to be that creature.
  2. (1:22): What does contemporary neuroscience tell us of the veridicality of perceptual experience? Neuroscience, physics, … even philosophy tell us that what we perceive is far from veridical. Evolution has done well to build us perceptual systems so that what we perceive really seems to be properties of the world. But, think about what that would imply. Colours: we’ve known since Newton that colours don’t have objective existence out there in the world. it’s only electromagnetic radiation – our eyes are sensitive to certain wavelengths. From that thin slice of reality, we construct a world of infinitely many colours, which only exist in the interaction between our brains and the physical world. Colours are a useful device – hit upon by evolution – for our systems to track how surfaces change under difference lighting conditions, allowing us to interact with the world. But “green” doesn’t exist either “out there” or “in here” – only in the interaction: it’s a construction. Easy to appreciate for colour, but Seth thinks it applies to everything else too.
  3. (3:05): While it’s possible to understand this intellectually – says Warburton – it’s almost impossible to “think it”, even in the case of colours: green seems to be so much part of the tree. Seth says such experiences are “cognitively impenetrable” – knowledge doesn’t change the experience. Also, Seth is not saying that “everything is in the mind”. As far as he knows, there is an objective reality out there. But, it’s how that reality appears in our experience that’s always a construction. Locke made the distinction between primary and secondary qualities. For primary qualities there’s a close resemblance between our experience and things in the world – solidity and movement, for instance. Colours are secondary qualities and the relation between experience and what’s out there is more indirect and requires the participation of the observer to generate the quality. Even so, the stuff is still out there and experience is not a hallucination or completely arbitrary construction.
  4. (4:24): Warburton say that – even with the green – there’s a story to be told in terms of “corpuscles”, the molecular structure of surfaces and an appropriate perceiving brain. We assume – given our similar perceptual equipment, that we all have a similar experience. Seth agrees, but says that “solidity” doesn’t require the same consensus amongst brains: a train will still cause you damage even if you’re not looking at it. But it’s a dangerous assumption that we do all perceive something like colour all the same – we almost certainly don’t. We see relatively sharp boundaries in rainbows whereas wavelengths change continuously. So, we’re imposing these categories to distinguish the colours. We should think of perception as inference or “best guessing”. Going back to Kant – the objective world is this unknowable stuff hidden behind a sensory veil and the objects of our perception are the brain’s “best guesses” of what’s behind. So, the sensory data itself is colourless, soundless, odourless but is used to continuously update the perceptual “best guesses”, which is the content of what we perceive. So, rather than perception being a bottom-up process whereby the brain reads out sensory data at different levels of complexity: edge → square → part of a train. In fact, perception works mainly in the opposite direction – from the top down or inside out. Not only do our predictions shape what we experience – we’re all familiar with seeing what we expect – but our predictions really are what we perceive. This is the inversion between thinking of perception as it seems, which is that there’s a world out there and sensory signals come in … we do some processing and recover what’s actually out there. When you flip that around, then you think that perception is all coming from the inside out and the top down and the sensory signals are just calibration signals: they don’t even have to be right – just useful. So, sensory signals just tell us “can our models be a bit more useful” and can we update the model? It really is an inversion because it doesn’t feel like that – it still seems that we are taking is sensory information .
  5. (7:38): Warburton: the last 20 years have been very dramatic in the kinds of breakthroughs that have been made in neuroscience. Do you think that we’re at the brink of really understanding consciousness? Seth thinks that in some sense nothing has changed in the 20 years he’s been working in this area. The big mystery is still there – we still don’t know the relationship between conscious experience and stuff that we call matter. There’s still the appearance of a big metaphysical mystery in trying to explain consciousness in terms of physics and biology. But then if he thinks how perspectives have shifted in the last 20 years, the big mystery – while still somewhat there – is less overbearing. We understand a lot more about perception, the Self, about the difference between sleep and wakefulness, dreaming and anaesthesia, even if we’re not sure what frame they all fit together in. Seth’s hope is that the trajectory of this research is a bit like what happened with the mystery of life. Not log ago, people thought that life was outside any sort of physical explanation – that you needed an élan vital – but that’s not necessary. While we don’t understand everything about life, the metaphysically difficult aspects about life is no longer present – we accept that it’s a natural phenomenon. If it goes the way of life – as we start to understand more about why we experience things the way we do, what the relationship is between the phenomenological properties of consciousness – the redness of red – and these mechanisms of prediction that go on in our brain, then the overall mystery of what consciousness is will start to fade away and we’ll start to come up with a satisfying science of consciousness that allows us to predict, control and explain all the things that we want to explain about conscious experience. Seth’s hope is that will pan out, but we won’t know unless we keep trying. (10:00)

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