Perception as controlled hallucination


EXCERPT (Andy Clark): . . . Predictive processing starts off as a story about perception, and it's worth saying a few words about what it looks like in the perceptual domain before bringing it into the domain of action. In the perceptual domain, the idea, familiar I'm sure to everybody, is that our perceptual world is a construct that emerges at the intersection between sensory information and priors, which here act as top-down predictions about how the sensory information is likely to be. [...] If you begin to ask what these stories have to say, if anything, about the nature of human consciousness, there are several things to say. The first is that the basic construction of experience is already illuminated just by thinking in terms of this mixture of top-down expectations and bottom-up sensory evidence and the way that mixture gets varied in different contexts and by different interventions...

[...] Perception itself is a kind of controlled hallucination. You experience a structured world because you expect a structured world, and the sensory information here acts as feedback on your expectations. It allows you to often correct them and to refine them. But the heavy lifting seems to be being done by the expectations. Does that mean that perception is a controlled hallucination? I sometimes think it would be good to flip that and just think that hallucination is a kind of uncontrolled perception.

The basic operating principle here is that you have a rich model of the world, a generative model, as it's known in this literature. What that means is a model that is not a discriminative model which just separates patterns out and says, "This is a cat and this is a dog," but rather a system that, using what it knows about the world, creates patterns that would be cat-like patterns or dog-like patterns in the sensoria. These systems learn to imagine how the sensory world would be, and in learning to imagine how the sensory world would be, they use that to do the classification and recognition work that otherwise would be done by an ordinary feed-forward discriminator. What that's doing is making perception and imagination and understanding come very close together. They're a cognitive package deal here, because if you perceive the world in this way, then you have the resources to create virtual sensory stuff like that from the top down.

Systems that can perceive the world like this can imagine the world, too, in a certain sense. That grip on the world seems to be very close to understanding the world. If I know how the sensory signal is going to behave at many different levels of abstraction and at many scales of space and time, so I can take the scene as it currently is and project it into the future and know what's going to happen if you hit the can and so on, that way of perceiving the world seems to me to be a way of understanding the world.

It will be very reasonable to ask where the knowledge comes from that drives the generative model in these cases. One of the cool things is that learning here proceeds in exactly the same way as perception itself. Moment by moment, a multilevel neural architecture is trying to predict the sensory flow. In order to do better at predicting the sensory flow, it needs to pull out regular structures within that flow at different time scales, so-called hidden causes or latent variables. Over time, with a powerful enough system, I might pull out things like tables and chairs and cats and dogs. You can learn to do that just by trying to predict the sensory flow itself.

It's interesting then to ask, if your models are playing such a big role in how you perceive and experience the world, what does it mean to perceive and experience the world as it is? [...] I don't think there's a good answer to that question. [...] An upshot here is that there's no experience without the application of some model to try to sift what is worthwhile for a creature like you in the signal and what isn't worthwhile for a creature like you. And because that's what we're doing all the time, it's no wonder that certain things like placebo effects, medically unexplained symptoms, phantom phone vibrations, all begin to fall into place as expressions of the fundamental way that we're working when we construct perceptual experience. In the case of medically unexplained symptoms, for example, where people might have blindness or paralysis with no medically known cause, or more than that, very often the symptoms here will have a shape that in principle can't have a simple physiological cause.

[...] In this broad sense of beliefs, it doesn't mean beliefs that you necessarily hold as a person, but somehow they got in there somehow. These multilevel systems harbor all kinds of predictions and beliefs which the agent themselves might even disavow. Honest placebos do work. [...] One of the effects of the general predictive processing story is that all of this is just sensory evidence thrown in a big pot. How I perceive the external world to be can be constantly inflected by how I'm perceiving my internal world to be. You see this, for example, in experiments where people are given false cardiac feedback. They're made to think that their hearts are beating faster than they are. And under conditions like that, if they're exposed to a neutral face, they're more likely to judge that the face is anxious or fearful or angry. It looks as if what's going on is that our constant intouchness with signals from our own body, our brains are taking as just more information about how things are.

[...] there's a Jamesian flavor to some of the work on experience that comes out of predictive processing where the idea is that emotion, for example, is very much tied up with the role that interoception plays in giving us a grip on how things are in the world. William James famously said that the fear we feel when we see the bear has a lot to do with the experience of our own heart beating and our preparations to flee, all of that bodily stuff. If you took all that away, perhaps the feeling of fear would be bereft of its real substance.

[...] The thing that I don't think is real is qualia. To understand that, we need to take a more illusionist stance... (MORE- details)

Arguably a good overview of some insights extracted from ongoing research. Until that departure at the end into the useless illusionist, phenomenal nihilist, or "qualia aren't real" stance. Or to fully clarify: The "qualitative properties and the showing of anything isn't real" view. Setting aside the conflicting insanity of such meaning that you're actually seeing, hearing, and feeling "nothing" rather than "something" (how thereby would we have evidence for anything?)... We instead have to take...

"Not being real" as roundaboutly referring to experience and its content being of psychological classification. IOW, not existing in today's quasi-metaphysical or rationalist version of the external world derived from science accounts. The latter technical realm of "scientific realism" is devoid of phenomenal properties, is depicted by abstract narrative and quantitative descriptions, and thus is just a better or more disciplined installment in the "intellectual version of existence" tradition descended from the ancient Greeks.

"Qualia not being real" is a contemporary re-hash of the old primary - secondary properties distinction going back to Locke, Galileo, and Democritus that has been around for centuries. (Galileo on primary and secondary qualities... Scientific direct realism) IOW, nothing new, and offers zero deep explanation of how those novel properties arise from posited, existing building-blocks of matter (which are again devoid of qualitative characteristics and manifestation capability). Apart from the usual "magical conjuring" slash brute emergence of the correct procedural actions or correct complex of dynamic, structural relationships invoking them. Which in turn is just dualism in disguise, the older formulations similarly appealing to biological bodies summoning an immaterial or "materially non-real" agency at a certain stage of development.

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