The Experience Machine

Unboxing the Experience Machine

The number of neuronal connections carrying signals backward in this way is estimated to exceed the number carry signals forward by a very substantial margin.
The brain, at 2% of human body weight is estimated to account for around 20% of total bodily energy consumption.
The bulk of what the brain does is learn and maintain a kind of model of body and world - a model that can then be used, moment by moment, to try to predict the sensory signal. These predictions help structure everything we see, hear, touch, and feel.
As a brain encounters new sensory information its job is to determine if there is anything in that incoming signal that looks like important "news" - unpredicted sensory information that matters to whatever it is that we are trying to see or do.
Hermann von Helmholtz - "given everything I know, how must the world be for me to be receiving the pattern of signals currently present?" This is the question that perceptual systems are built to resolve.
If the signal is poor, the brain chruns out "good hallucinations" by filling in and fleshing out the missing signal according to what it expects to hear.
The "top-down" flow of information
"Controlled hallucination" - When inner guessing completely rules the roost, we are just hallucinating, full stop. But when it is appropriately sensitive to sensory stimulations - via prediction error signals - the guessing is controlled, and the world becomes known to the mind.
Linear predictive coding (Cluade Shannon) - The trick is trading intelligence and foreknowledge against the costs of encoding and transmitting all the information. Transmit only whatever turns out to be different from the predicted patterns. Wherever there is detectable regularity of any kind, prediction (and hence this form of data compression) becomes possible.
However complex or high-level the predictions, it is prediction errors that must then carry the news, signaling differences from the expected and thereby keeping us in touch with a changing and sometimes surprising world.
In the predictive processing architecture of the brain, it is thought that different neuronal populations specialize in different things, so that each "higher" level can use its own specialized knowledge and resources to try to predict the states of the level immediately below it. A level that specializes in predicting whole words might use its knowledge to help predict states at a lower level whose specialty is recognizing letters. The word level might be predicted by a higher level that specializes in sentences.
All that flows forward is news - deviations from what is expected. This is efficient.
Our own actions and histories sculpt the onboard prediction machinery that in turn sculpts human awareness, right down to the level of what seem to us to be basic sensory experiences.
Millions of years of evolution have determined the bedrock configuration of the machinery we command at birth: the early wiring of the brain, the structure of our sense organs, and the shape of our bodies. Courtesy of all that, we start our journey already armed with plenty of hard-won knowledge.
Creatures with lungs are already structurally "expecting to breathe".
Creatures like us specialize in learning about their worlds on the basis of repeated sensory encounters. And we drive learning by trying to predict our own sensory flows.
The brain learns by looking for better and better ways to predict that unruly sensory barrage. Very young infants seem to spend most of their time doing just this, trying to find useful patterns in the sensory stream.
One way to predict quite a lot about the most likely next word in a sentence is to implicitly know a lot about grammar. And a good way to learn grammar is to try, again and again, to predict the next words you are going to hear. As those attempts continue, your brain can slowly, unconsciously, discover the regularities that will enable you to do a better job.

Psychiatry and Neurology - Chronic Pain, Autism, Schizophrenia, and PTSD

Types of pain:
- Nociceptive pain - indicates actual or threatened bodily damage
- Neuropathic pain - is caused by damage or disease affecting the sensory systems that deliver the experience of pain, or the processing of pain information.
- Nociplastic pain - arises form abnormal processing of pain signals without any clear evidence of either tissue damage or any other recognized systemic pathology.
Human experience arises at the meeting point of predictions and sensory evidence and this meeting is flexibly determined by the brain's best estimate of their relative reliability and significance (precision).
Only predictions that our brains estimate to be reliable get to exert a powerful influence on our sensations. If you don't trust an authority, then all bets are off.
Placebo-induced chagnes have been shown to reach far down, altering responses even at the level of the spinal cord. Our active expectations of pain or relief are somehow impacting the whole web from which experience itself is constructed.
False expectations, once they get a grip on us, become increasingly resistant to change.
Functional neurological disorders are entirely genuine but appear not to be caused by any kind of anatomical or structural change or conventional disease process.
Precision variations control which bits of what we know and what we sense will be most influential, moment by moment, in bringing about further processing and actions. Precision variation is what attention really is.
Attention is the brain adjusting its precision-weightings as we go about our daily tasks, using knowledge and sensing to their best effect. By attending correctly, I become better able to spot and respond to whatever matters most for the task I am trying to perform. Precision estimation is thus the heart and soul of flexible, fluid intelligence.
Strongly anticipating pain, numbness, weakness, or other symptoms alters patterns of attention (precision-weightings) in ways that can either amplify or entirely generate the experience - which then seems to confirm those very expectations.
There is no such thing as raw or correct experience of a medical symptom.
After several bouts of back pain, people start to process the world differently... their pain becomes embedded among the things they associate with themselves.
We need to move away from thinking of pain as a simple sensation, a direct signal of damage or potential damage, to a view of pain as a perception.
There are two ways for predictive processing to go wrong:
- Underweight predictions and expectations (underuse the brain's predictive powers) - making it hard to detect faint but predictable patterns in a noisy or ambiguous environment.
- Overweight expectations (ignoring environmental conditions) - in extreme cases, this leads to hallucinations.
Evidence now favors the idea that a tendency to overweight the sensory evidence (enhanced sensory precision) is the core difference separating autism spectrum condition from the more neurotypical profile. Autism spectrum individuals constantly encounter an excess of highly detailed and apparently very salient sensory information, coming from both inside their own body and the outside world. This sensory excess impedes the moment-by-moment identification of the broader context or scenarios. The emphasis on every aspect of sensory detail effectively makes it impossible to spot the larger forest for the trees.
Faced with an endless stream of rich and apparently attention-demanding sensory information, an individual with autism spectrum condition might start to self-select more predictable environments, becoming increasingly wary of complex social encounters. Repetitive and stereotyped behaviors such as rocking or hand-flapping might also emerge, as these would offer a clever way to ensure (by self-generating) a predictable streams of sensory input. Yet another way to reduce sensory surprises is to develop extreme expertise in a restricted domain.
Schizophrenia - Falsely generated, highly weighted prediction error forces the brain to seek a new predictive model. The resulting hypotheses (shadowy organizations, telepathy, alien control, and strange beliefs involving the internet), may appear bizarre to the external observer. Yet from within they constitute the best explanation available.
During the onset of psychosis, the world begins to look somehow different or strange, reflecting the presence of persistent, unresolved prediction errors. Those errors then slowly drive the system to form increasingly radical hypotheses in an effort to accommodate them.
Predictive brains control action as well as perception, so the delusional person will actively seek out confirming evidence for their radical hypotheses. New information may itself be interpreted differently so as to appear to confirm or consolidate the radical beliefs. The cycle of error thus becomes viciously self-protecting. Such pernicious outcomes seem to be the Achilles heel of the predictive brain.
Up to 30% of those exposed to a highly traumatic event will go on to develop some form of PTSD, which is well correlated with unusually large increases in precision-weighting on the prediction error signal in response to unexpectedly negative outcomes. In the most severely affected individuals, the response to failing to predict the showk was to radically overweight the missed cue and thereby become hypersensitive to its occurrence in the future.

Action as Self-Fulfilling Prediction

The brain predicts how things would look and feel if the action were being successfully performed, and by reducing errors relative to that prediction, the action or movement is brought about. Predicting just how it would look and feel to hit that perfect drive, or make a killer serve, brings that longed-for result about.
By making prediction the common root of both perception and action, predictive processing (action inference) reveals a hidden unity in the workings of the mind. Action and perception form a single whole, jointly orchestrated by the drive to eliminate errors in prediction.
Actions come about because we mentally represent the completed effects of the action. Representing some desired end result, such as grasping a cup, automatically recruits (in the skilled agent) the set of motor commands needed to make that very thing happen.
The brain learns, through training and experience, to predict what we would see and feel if - but only if - our bodies were moving in just the right ways so as to achieve our goals.
By predicting the specific sensory effects of that motion, and then rapidly quashing the errors that resulted by actually moving my head and eyes in the right ways, I brought into view the scene outside my window.
By launching a cascade of sensory predictions, and then rendering them true by means of action (thus eliminating the resulting prediction errors), the brain creates the desired movements. I strongly predict looking out the window and that prediction acts as a kind of self-fulfilling prophecy.
Motor control works in much the same way as perception. In each case, the brain is seeking to achieve a fit between what is predicted and what the sensory evidence suggests. But in the case of action, the fit is achieved by altering the sensory evidence to bring it into line with the prediction.
To move my arm, I must give high weighting to the desired future state (arm moving) rather than the undesired present state (arm not moving). That means actively disattending to the present state of the arm, hence dampening down that sensory information.
For many processes, waiting for feedback cues (such as wilting plants) is a bad idea, as what is really needed is ongoing preemptive action. Systems that instead predict the future from their current state, current actions, and a model of how those actions will affect that state, are always one step ahead of the game.
Active sensing - Sensing itself is an intelligent action, aimed at delivering just the right information, just in time for use. As embodied agents we are able to act on our worlds in ways that actively generate new patterns of sensory stimulation.
Expert seeing
Goal-directed behavior involves using predicted outcomes to help structure the actions that will best serve to make those outcomes real.
If I plan to become a better surfer, my brain needs to make the realistic-yet-optimistic prediction that I will indeed later be such a surfer. With that goal (long-term prediction) active, I can use what I know about how things work in the world to identify important steps along the way, generating a policy that might - according to my current skill set and personal circumstances - include moving to the coast, taking classes, or vacationing in Tarifa.
Realistic optimisim - We must at some level strongly predict that we will occupy the states that we can plausibly attain and that best realize our goals. We wil then act in ways designed to eliminate errors calculated relative to the optimistic-yet-realistic prediction that those goals are achieved.

Predicting the Body

Dark Room puzzle - why not just seek out a dark empty corner and just stay there until you die?
The primary task of all the prediction machinery in our heads is to help us stay alive. A major part of that staying alive involves keeping our own inner bodily states within the surprisingly tight bounds of biological viability
Homeostasis and Allostasis:
- Homeostasis (from the Greek "same" and "steady") - A tendency to return to a state or to return to a place within a range. To maintain a viable set of internal conditions despite external fluctuations. Thermoregulation in humans is just one aspect of the rich web of inward-looking control and regulation.
- Allostasis - Highlights the need to alter the ranges themselves so as to adapt to changing needs and environments. Humans do this when we respond to worries and threat by increasing cortisol levels. Cortisol isn't just a stress hormone, but rather a part of the system that prepares u for the kinds of actions our brain predicts are on the near horizon. Rather than waiting for something to go awry, then using negative feedback to bring things back into line again, predictive models allow us to make early, pre-emptive responses. This is why we feel the need to eat and to sleep long before our blood sugar levels drop too low, or our energy resources become really run-down. Feelings of hunger and tiredness are for the most part signals not of present needs but of predicted, impending challenges: challenges that left unchecked would lead us too far from the safe bounds of physiological viability and health.
Three sensory systems:
- Interoceptive - Inward-looking
- Exteroceptive - Outward-looking (including vision, touch, and hearing)
- Proprioceptive - Implicated in motor control, informing the brain about the position and orientation of our bodily parts in space
The athlete perspires, and the academic leaves the life-threatening Dark Room and heads for the restaurant.
Feeling good tends to favor exploration and engagement, whereas feeling bad tends to favor retreat and conservation.
Estimations of error dynamics track how well we are currently doing at minimizing prediction error versus how well we (our brains) were expecting us to do. Are things going better or worse than expected? Things are going better than expected if we are fluently eliminating more (and more important) errors than anticipated. Things are going worse then expected if we are encountering more errors, or dealing with them less fluently, than anticipated. The feeling of "being in the zone" in sports reflects unexpectedly good error dynamics of this kind.
Creatures sensitive to their own error dynamics will automatically seek out good learning environments, preferring ones that are neither too predictable not too unpredictable. In the former, there's nothing much to learn, so the error dynamics are flat. In the latter, learning is too hard and errors are not eliminated. Good error dynamics arise in between these extremes.
Positive and negative moods and feeling are thought to be reporting these important error dynamics, bring them forcefully to our attention by making some events and situations simply strike us as way more pleasant and fulfilling than others - a good day on the tennis court, or in the office, when you are really "in the zone" for whatever you are trying to achieve, versus a day when every minor task seems like an uphill struggle.
Babies spend their time on tasks that deliver learning at a good or better-than-expected rate. This means confronting - and sometimes actively creating - a kind of controlled uncertainty. A toddler may try to build a Lego tower that is just a bit bigger than the last one they managed. Babies, infants, and toddlers all seek out and prefer "just-novel-enough" situations - the ones on the edge of their competencies and understanding that will deliver the right kind of learning opportunity.
Artificial curiosity - simulated animals that were drawn to the Goldilocks zone consistently outperformed rivals lacking that inbuilt drive. This was especially true in simulated environments where change and volatility were the norm. This makes good sense since dealing with such environments puts a premium on rapid leaning and cognitive flexibility.
Body budgeting - tracks and anticipates the use and replenishment of key resources for maintaining bodily life and functioning, like water, salt, and glucose. To renew them, we engage in familiar activities such as finding and consuming food and sleeping. Allostatic mechanisms are vital to this process.
Both the feeling of thirst and the feeling of having quenched your thirst each reflect anticipatory processing.
Every thought, memory, emotion, or perception that you construct in your life includes something about the state of your body. Your interoceptive network, which regulates your body budget, is launching these cascades. Every prediction you make, and every categorization your brain completes, is always in relation to the activity of your heart and lungs, your metabolism, your immune function, and the other systems that contribute to your body budget.
The predictive engine is mastering a melting pot of influences when it delivers and experience that I might label as feeling sad or anxious.
The central idea is that a single kind of process combines inner and outer sources of information, generating a context-reflecting amalgam that is experienced as emotion.
The anterior insular cortex (AIC) mediates this process.
According to interoceptive predictive processing, emotions and feelings reflect a process that combines interoceptive (inward), proprioceptive (action-guiding), and exteroceptive (outward) information with model-based predictions of all those signals as they are occurring.
There is growing evidence that cortical and subcortical areas evolved in a highly coordinated fashion that produced rich interdependencies. What resulted is a complex looping arrangement linking cortical and subcortical structures in a web of continuous two-way influence. In these tangled webs, each element is constantly affecting, and being affected by, the others. It is this looping circuitry that keep our higher-level prediction machinery in direct contact with our own unfolding bodily states, actions, and their worldly consequences.
Because so many subcortical circuits are tightly coordinated with internal bodily processes (vascular, visceral, endocrine, autonomic), all manner of information from the body becomes positioned to play a much more important and ongoing role than we assumed by the older corticocentric vision of the brain. Thanks to these constant looping dynamics, body, brain, and world become equal partners in the construction of thought, experience, and action.
Depression is often best seen as a disorder of allostasis. It involves mistaken forms of bodily prediction involving energy regulation and, like other chronic psychiatric conditions, is surprisingly resistant to new information, with problems either generating or learning from the prediction error signal.
Locked-in brain - Suppose that you experience a succession of unexpectedly negative social events. These all result in social prediction errors. You may start to compensate by mistakenly increasing the weight on small social cues, including all the many signals (facial, verbal, and those involving body language) that help us navigate stressful or important social situations. Faced with all that extra noise, now masquerading as information, you may start to adopt what has been described as a kind of "better safe than sorry" strategy so as to avoid most social interactions, since their outcomes seem increasingly unpredictable.
Such maladaptative patterns are often seeded by early experiences such as abuse or neglect that lead us to believe that social rewards are unlikely and social outcomes unpredictable.
A kind of "cognitive immunization" against countervailing positive information, causing us to either avoid gathering, ignore, or otherwise downgrade perfectly good positive evidence - such as genuine evidence that we are like and valued.
If it is on the right track, depression is never simply a disorder of mood. It is a disorder of the whole body-brain-environment system, affecting the way the brain forms and runs bedrock bodily energy budgets, and the way it responds to new positive and negative information.
Salience detection hypothesis - these chills occur when we encounter something that our brain identifies as critical new information that resolves important uncertainties. This makes it a kind of physiological echo of the "aha" moment when things suddenly fall into place.
The power of great music and literature lies in its ability to lead us through a staged process that first reliably builds up and then reliably resolves expectations.
Probability designs - artifacts engineered to interact in reliable ways with our own predictive brains. Books, novels, plays, and movies are all probability designs. Attention (precision-weighting) plausibly plays a key role here, adding impact to the musical items that portend key moments in the movement or symphony. Aesthetic chills are a physiological marker of this sudden increase in estimated importance (precision).
Our take on the outside world (the way things look, taste, feel, and sound) is in constant two-way communication with information and predictions about our own changing internal physiological states. When this all works in harmony, it keeps us from straying too far from our window of bodily viability, and proactively budgets for our basic bodily needs. But when this system malfunctions and misregulates, it can lead to depression, anxiety, and retreat from the world. Bodily prediction helps sculpt an experiential world in which some states and events are simply more attractive (hence more likely to be occupied) than others. This enables living beings to bring forth meaning and mattering from an otherwise meaningless material flux.

The Hard Problem - Predicting the Predictors?

Sentient beings - those whose neural model of the world is in constant two-way communication with a model of their own changing physiological state. They live, we might say, in a world that is temporally extended and perceptually meaningful. Bodily self-regulation, action, and temporal depth are, predictive processing thus suggests, jointly necessary if there is to be conscious experience at all.
What could be going on when we humans go one step further and start spontaneously to report (and puzzle over) the presence, in our own experience of all those distinctive looks, feels, and qualia?
Once in command of a structured predictive model, we may quite easily spot some never-before-seen object as being a new kind of cute animal, sweet treat, car, or food mixer. We can do this because our own prior learning experience has in each case allowed the brain to lock on to a complex of subtle interlocking cues and features. These can later be spotted when they co-occur, even in brand-new instantiations.
Sentient, feeling beings: beings that find themselves in a world where things really matter.
All that nature cared about when building us was that we be able to detect what's out there (is that a predator or a friend?) and how things are physiologically, whether we need food, water, or rest, or to avoid injury. Adding machinery to enable us to appreciate the full complexities of our own inner processing would have been costly and quite possibly counterproductive, diverting attention from what really matters in body and world.
Self-opacity and simplified self-models lead us - clever but limited beings - to infer that we are home to a mass of extremely puzzling qualitative states. But these inferred qualia are just another handy tool for predicting ourselves and others. The underlying states (sentient beings' best guesses at how things are in body and world) are real. But our profound metaphysical puzzlement is mistaken. Qualitative consciousness is real. ut perhaps it isn't exactly what we think.

Expecting Better

Strong emotions, in predictive processing, are associated with high estimated precision - so the brain is treating that information as unusually significant and reliable.
People with anxiety are often very internally focused, while at the same time surprisingly bad at knowing their own heartbeat. They focus hard on their own internal state but do so without much accuracy or precision.
Participants with better interoceptive self-awareness were also better able to detect the emotional information "hidden" in other people's speech intonations.
The most basic way that we actively construct our world is by selective sampling. We move our body and aim our gaze in ways that reflect what we expect to encounter. In this way, different kinds of animals, and humans with different individual histories, will harvest different sets of stimulations from the very sam world. But as we selectively harvest those stimulations, our brains impose structure as second time, processing the sensory information in ways that amplify and dampen, extracting meaningful structure that itself reflects our own prior experience. The "predictive keyboard" is thus not just an active selector, but also an active processor of whatever gets selected.
Our physical world itself exerts an admirable tendency to resist wildly mistaken guesses at its shape and powers.
There are also many shared features that characterize human bodies, brains, and nervous systems, anchoring the construction of a shared human reality.
So human experience reflects a shifting amalgam of these deep-set structural constraints and flexible, higher-level, top-down influences.

Beyond the Naked Brain

The extended mind
We all rely, to greater or lesser degrees, upon a wide array of apps, tools, and other "beyond the brain" resources to carry out our daily projects, to organize our lives, and to remember to do things that we'd otherwise forget. Some of these aids function in ways that seek to replicate or bolster skills and abilities already possessed by our biological brains. Others play even more intriguing roles - not simply replicating native biological capabilities, but enhancing and transforming them.
Epistemic actions - actions selected to improve our state of knowledge rather than to directly achieve some practical goals.
Predictive brains do not care whether key information is stored in their own internal states and structures or outside, in notebooks, apps, and GPS systems. What matters is just that the right information or operations are predictably available as and when needed for the fluid control of behavior.
We humans often tackle problems by recruiting external props and tools, in many cases reducing the more complex puzzles to sequences of simpler ones that our biological brains could more readily handle.
What goes on inside the head might often be simpler than we have imagined. It might also be simply different, in that much of the real work of the embodied brain now consists in learning the right strategies for interacting with the external world.
The human mind is a "leaky system" - apt to lean on the surrounding world in heavy and sometimes surprising ways.
For patients living independently with Alzheimers, their homes and local environments took over some of the functions that were previously played by their biological brains.
We are "natural born cyborgs" - the suite of capabilities that make us who and what we are is often best understood as the larger hybrid whole.
Our minds and selves can become so intimately bound up with the worlds we live in that damage to our environments can sometimes amount to damage to our minds and selves.
Playing Scrabble, shuffling the tiles prompts the biological brain with new potential word fragments.
The expert bartender has learned to sculpt and exploit their working environment in ways that transform and simplify the task that confronts them.
The seamless intermingling or epistemic and practical moves in expert play suggests the operation of a single overarching strategy - which is exactly what work on the predictive brain now provides.
The distinction between the epistemic and non-epistemic elements becomes fuzzy and potentially vanishes entirely.
Practical actions and epistemic actions are determined in exactly the same way, as the predictive brain makes counterfactual predictions about what kinds of futures will result if certain actions are launched. Actions are then chosen that deliver preferred outcomes directly (when possible) or else that probe and sample the environment to bring forth more information, reducing key uncertainties, and making the desired outcome more likely in the future. Practical and epistemic actions both flow from that same deep source and serve a common goal.
Once a system can compute expected future error, it will automatically seek out the interwoven set of practical and epistemic actions most likely to bring the desired future state about.
By having a good predictive model, a player can preemptively look toward locations where there is currently nothing going on but where they predict that crucial information as about to appear. In soccer, a player will often look to the spot where they think a pass will soon be made. The control of these epistemically motivated head and eye actions must depend on predictions rather than here-and-now perceptions, as there's often absolutely nothing of any interest going on at that location just yet. These information-seeking forays must often be launched at just the right moment if they are to lead to sporting success.
This kind of predictive skill develops with expertise.
Writing this book:
- The text didn't somehow spring fully formed from my brain. Instead, my brain acts as a constant facilitator of a stack of repeated interactions with various external resources.
- As these resources (old notes, key articles, web pages, and online discussions) are encountered, my brain reacts in a fragmentary way to each, very occasionally delivering new ideas that lead to further notes and scribbles.
- These are repeatedly refined, re-encountered, and transformed in what is best seen as a rolling, extended process of thinking and text construction.
- In these ways, many of our prime cognitive achievements should not be credited solely to our biological brains but depend heavily upon the enabling environments in which we act and perceive.
Inside the human gut, where upward of 500m neurons in the gut wall already relay important information to the spinal cord and the brain. This circuitry helps regulate serotonin and other neuromodulators. The so-called gut-brain is by a long margin the largest cluster of neurons outside the brain, and an essential part of the nervous system. It is pretty clearly part of what makes you who you are and has a major influence on what you think and feel.
Gut bacteria manufacture up to 95% of the body's serotonin, which has large impacts on mood and is one of the neurotransmitters implicated in the precision-weighting process.
Successful organisms are thus much more than instances of simple genetic lineages. They are collaborative ecologies that require a wide variety of contributions.
Woven resources - trusted nonbiological structures that are delicately and constantly couple to the rest of the system that we recognize as you. Many of our daily devices, especially our smartphones and other wearables are already starting to act as woven resources.
The extended mind - when the weave between the brain's activities and the functionality of some nonbiological resource becomes sufficiently tight, it really is better to think of that person's mind as an extended mind - a new problem-solving architecture built from an array f resources spanning brain, body, and world.
Minds are not merely what brains do. They are what brains create - distributed cognitive engines spanning brain, body, and world.
Perhaps it is perception and action, not skin and skull, that best serve as the boundary of the mind? Otto reaches for the notebook as thoughtlessly and automatically as Inga "reaches" for her biological recall.
The predictive brain is here engaging in a kind of "knowledge budgeting" akin to body budgeting - selecting policies and actions that will steadily, and at just the right moments, deliver the knowledge and information needed to approach our long-term goals.
In between the Large Hadron Collider and my smartphone lie a vast swath of resources that are less trusted, demand more attention, and are (as a result) more loosely woven into my daily life.
My top-level goals set off sequences of actions that call upon external epistemic aids to minimize future prediction error. In this way, the weaving in of the right external resources "just happens" - it is not the result of effortful deliberation. Where minds extend, external epistemic actions should arise and dissolve as fluently and effortlessly as their internal counterparts.
As predictive processing unfolds, human experience and human thinking are orchestrated from the inside by neuronal activity and the dense network of brain-body interactions, and from the outside by the highly structures social and technological worlds in which we live and act. This creates a circular causal web in which mind is - at the very least - constantly porous to body and world.

Hacking the Prediction Machine

Human experience is shaped by the flow of predictions, so that our every waking moment reflects not just what is coming in from the outside world, but what our brain expected to be coming in. Experience happens only when these forces collide.
It is only confident predictions (even if they are ones hidden from conscious view) that get to exert a real grip on the shape of human experience.
Honest placebos appear to work by activating subterranean expectations through superficial indicators of reliability and efficacy such as good packaging and professional presentation (foil and blister packs, familiar font, size and uniformity of the pills, and so on). This is because the bulk of the brain's prediction empire is nonconscious.
Repeated administration of the actual (clinically effective) drug seems to teach the brain-body system to predict a very specific cascade of pain-relieving responses, many of which can later be re-created or approximated by the patient's own endogenous opioid system. Experience with the effects of taking the real drug have managed to teach the body how to respond, and the body can then mount those responses for itself when encouraged (by the placebo) to do so.
Some individuals are experts at "phenomenological control" - the capacity to exert a kind of unconscious control over the shape of their own experience.
VR treatment can work thanks to its immersive environment, which acts like a magnet, requiring the brain to scramble to make sense of this new and constantly shifting environment. Increased precision over this new sensory information means decreased precision over other sensory information, including information regarding pain.
Reframing pain by talking and thinking about our feelings and sensations in a slightly different way, we enable our brain to reshape its own prediction landscape.
Cyberdelics - Psychedelic drugs can help by "shaking the snowglobe" - jolting the mind out of entrenched negative patterns, making it more flexible and open. what had seemed like deep, immovable facts about how things are (and ow you are) release their stranglehold, allowing other ways of seeing the world and "being you" to emerge.
Huxley thought of ordinary perception as a kind of "reducing valve" that blocked out most of the true structure of the world, delivering merely the "trickle" most helpful for survival - mentions sensory blockage, unblockage, and subsequent revelation.
Psychedelic drugs exert their strongest effects at higher levels of cortical processing. They are likely to be impacting higher-level (increasingly abstract) elements of the predictive model of self and world, concerning who we are, what we want, and how we conceive of reality. They also dampen the activity that communicates predictions between different neuronal populations and the activity of key brain networks (including the default mode) that are especially active during self-centric thinking and rumination.
But they decrease, rather than increase brain activity. They relax the grip of higher-level expectations concerning self and world, allowing different flows of information to emerge and interconnect in new ways, less constrained by our ingrained top-level expectations.
At higher doses, they seem to reduce the precision-weighting on highly abstract top-level self-predictions, thus releasing bottom-up sensory and bodily information, and allowing it to play a larger role. They may have benefits for anyone/everyone who might learn by experiencing their world in a less entrenched and ego-driven way.
Meditation can provide a "holiday from the self". By focusing attention on the breath, it drops the precision assigned to all other states, down-weighting all the rest of the information flowing in from the senses, and allows a kind of freezing of longer-term anticipatory processes, preventing the kinds of counterfactual looking ahead that play such a large role in daily behavior. In this way it can provide a new lever for the control of previously automatic aspects of neural activity - in this way meditation can really "control attention". Sensations, fears, hopes, and memories can then be experienced without engaging the usual wheels of judgement, rumination, and calls to action.

Ecologies of Prediction, Porous to the World

Nothing in human experience comes raw or unfiltered. Instead everything is a construct arising at the many meeting points of predictions and sensory evidence.
Our brains do not simply sit there waiting for sensory stimulations to arrive. Instead, they are buzzing, proactive systems that constantly anticipate signals from the body and from the world. These are the brains of embedded agents, elegantly designed for action in the world. By moving our eyes, heads, and limbs we seek out the sensory signals that will both test and (usually) confirm our predictions. Experience takes shape as predictions of our own sensory inputs are tested, refined, and challenged in these ways.
The stronger our prior expectations (the higher their "precision") the less impact incoming counterevidence will have on what we see or otherwise perceptually experience. It is this precision-weighted balancing act that seems to be compromised in many forms of mental illness, functional disorder, and psychosis. There are also many different ways the balancing act can be performed, and these plausibly correspond to the wide sweep of neurodiverse ways of being in the world.
The bulk of the predictions and expectations that determine the shape of human experience are hidden from our own view and seldom formulated in words. but despite this, our brains are teeming with these active predictions and they impact everything we see, feel hear, and touch.
To perceive is to find the predictions that best fit the sensory evidence. To act is to alter the world to bring it into line with some of those predictions. These are complementary means of dealing with prediction error, and they work together, each constantly influencing and being influenced by the other.
Basic sentience occurs whenever a creature encounters its world as a meaningful arena for action - when it treats different states of that world as attractive or unattractive, as providing or foreclosing opportunities. by bring work on the predictive brain together with the role of actions, error dynamics, and internal bodily signals, we laid out the rough shape of a theory of sentience.
Once basic sentience is explained what remains is then mostly a set of misleading intuitions - cognitive illusions rooted in our peculiar, perhaps linguistically inculcated, abilities of self-reflection.
Human minds are seething, swirling oceans of prediction, continuously orchestrated by brain, body, and world. We should be careful what kinds of material, digital, and social worlds we build, because in building those worlds, we are building our own minds too.
Predictive minds are built of four core elements:
- A generative model
- Moment-by-moment predictions that it issues.
- Prediction errors which arise whenever incorrect or incomplete predictions attempt to meet and account for sensory evidence.
- Estimations of precision that alter the relative impact of both sensory stimulations and predictions. Turning up the volume on information that is estimated as both important (task salient) and reliable, ie this is attention, like a head-mounted flashlight that focuses on the world without effort.