41 | Being You - Anil Seth
What Does the Brain/Body Do?
“Whenever we are conscious, we are conscious of something, or of many things. These are the contents of consciousness. To understand how they come about, and what I mean by controlled hallucination, let’s change our perspective. Imagine, for a moment, that you are a brain.
Really try to think about what it’s like up there, sealed inside the bony vault of the skull, trying to figure out what’s out there in the world. There’s no light, no sound, no anything — it’s completely dark and utterly silent. When trying to form perceptions, all the brain has to go on is a constant barrage of electrical signals which are only indirectly related to things out there in the world, whatever they may be. These sensory inputs don’t come with labels attached (‘I’m from a cup of coffee’, ‘I’m from a tree’). They don’t even arrive with labels announcing their modality — whether they are visual, auditory, sensations of touch, or from less familiar modalities such as thermoception (sense of temperature) or proprioception (sense of body position)
How does the brain transform these inherently ambiguous sensory signals into a coherent perceptual world full of objects, people, and places? In Part Two of this book, we explore the idea that the brain is a ‘prediction machine’, and that what we see, hear, and feel is nothing more that the brain’s ‘best guess’ of the causes of its sensory inputs. Following this idea all the way through, we will see that the contents of consciousness are a kind of waking dream — a controlled hallucination — that is both more than and less than whatever the real world really is.” (Pages 75-76)
“Although it may seem as though my senses provide transparent windows onto a mind-independent reality, and that perception is a process of ‘reading out’ sensory data, what’s really going on is — I believe — quite different. Perceptions do not come from the bottom up or the outside in, they come primarily from the top down, or inside out. What we experience is built from the brain’s predictions, or ‘best guesses’, about the causes of sensory signals. As with the Copernican revolution, this top-down view of perception remains consistent with much of the existing evidence, leaving unchanged many aspects of how things seem, while at the same time changing everything.” (Page 80)
“When I look at a red chair, the redness I experience depends both on properties of the chair and on properties of my brain. It corresponds to the content of a set of perceptual predictions about the ways in which a specific kind of surface reflects light. There is no redness-as-such in the world or in the brain. As Paul Cezanne said, ‘colour is the place where our brain and the universe meet.’
The larger claim here is that this applies for beyond the realm of colour experience. It applies to all of perception. The immersive multisensory panorama of your perceptual scene, right here and right now, is a reaching out from the brain to the world, a writing as much as a reading. The entirety of perceptual experience is a neuronal fantasy that remains yoked to the world through a continuous making and remaking of perceptual best guesses, of controlled hallucinations.
You could even say that we’re all hallucinating all the time. It’s just that when we agree about our hallucinations, that’s what we call reality.” (Page 86-87)
“In predictive processing, action and perception are two sides of the same coin. Both are underpinned by the minimisation of sensory prediction errors. Until now, I’ve described this minimisation process in terms of updating perceptual predictions, but this is not the only possibility. Prediction errors can also be quenched by performing actions in order to change the sensory data, so that the new sensory data matches an existing prediction. Minimissing prediction through action is called active inference — a term coined by the British neuroscientist Karl Friston.” (Page 112)
“Why do we experience our perceptual constructions as being objectively real? On the controlled hallucination view, the purpose of perception is to guide action and behaviour — to promote the organism’s prospects of survival. We perceive the world not as it is, but as it is useful for us. It therefore makes sense that phenomenological properties — like redness, chairness, Cilla Black-ness, and causality-ness — seem to be objective, veridical, properties of an external existing environment. We can respond more quickly and more effectively to something happening in the world if we perceive that thing as really existing. The out-there-ness inherent in our perceptual experience of the world is, I believe, a necessary feature of a generative model that is able to anticipate its incoming sensory flow, in order to successfully guide behaviour.
To put it another way, even though perceptual properties depend on top-down generative models, we do not experience the models as models. Rather, we perceive with and through our generative models, and in doing so out of mere mechanism a structured world is brought forth.” (Page 138)
“The self is not an immutable entity that lurks behind the windows of the eyes, looking out into the world and controlling the body as a pilot controls a plane. The experience of being me, or of being you, is a perception itself — or better, a collection of perceptions — a tightly woven bundle of neurally encoded predictions geared towards keeping your body alive. And this, I believe, is all we need to be, to be who we are.” (Page 154)
“Self-perception is not about discovering what’s out there in the world, or in here, in the body. It’s about physiological control and regulation — it’s about staying alive.” (Page 171)
“At the very deepest layers of the self, beneath even emotions and moods, there lies a cognitively subterranean, inchoate, difficult-to-describe experience of simply being a living organism. Here, experiences of selfhood emerge in the unstructured feeling of just ‘being’. This is where we reach the core of the beast machine theory: the proposal that conscious experiences of the world around us, and of ourselves within it, happen with, through, and because of our living bodies. It is at this point that all of the ideas I’ve been putting forward about perception and self fall into place. So let’s take things step by step, from the beginning.
The primary goal for any organism is to continue staying alive. This is true almost by definition — an imperative endowed by evolution. All living organisms strive to maintain their physiological integrity in the face of danger and opportunity. This is why brains exist. Evolution’s reason for providing organisms with brains is not so they can write poetry, do crossword puzzles, or pursue neuroscience. Evolutionarily speaking, brains are not ‘for’ rational thinking, linguistic communication, or even for perceiving the world. The most fundamental reason any organism has a brain — or any kind of nervous system — is to help it stay alive, through making sure that its physiological essential variables remain within the tight ranges compatible with its continued survival.
These essential variables, whose effective regulation determines the life-status and future prospects of an organism, are the causes of interoceptive signals. Like all physical properties, these causes remain hidden behind a sensory veil. Just as with the outside world, the brain has no direct access to physiological states of the body, and so these states have to be inferred through Bayesian best guessing.” (Pages 187-188)
