I'm continuing to read and enjoy Andy Clark's The Experience Machine: How Our Minds Predict and Shape Reality. It's one of the best books about modern neuroscience that I've ever read, and believe me, I've read a lot of them.
My first post about the book laid a foundation for these subsequent posts, as I get deeper into The Experience Machine. This is a one sentence summary of the Big Idea discussed in the book -- which makes a heck of a lot of sense.
Predictions and prediction errors are increasingly recognized as the core currency of the human brain, and it is in their shifting balances that all human experience takes shape.
In a "Psychiatry and Neurology" chapter, Clark talks about prediction errors. Those are the difference between what the brain expects to perceive, given sensory inputs and prior experience, versus what is actually perceived.
Ideally those errors are reduced as we learn more about the slice of reality we're attending to.
But sometimes they aren't, which can create problems for us, big or small. Here's how Clark explains this. It won't be completely understandable, since I'm just sharing small excerpts from his book, but you should get the gist of his message.
Varying estimates of precision alter patterns of post-synaptic influence and so determine what (right here, right now) to rely on and what to ignore. This is also the way brains balance the influence of sensory evidence against predictions.
In other words, 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. Expressed like that, the intimacy of precision and attention is apparent.
Precision variation is what attention (a useful but somewhat nebulous concept) really is.
For example, suppose I want to find a needle recently dropped in a bed of hay. According to predictive processing, my brain ups the precision-weighting on specific aspects of the visual information that would indicate a small silvery object, thereby increasing my chances of success.
That's what attention, if these accounts are correct, 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.
But what happens when precision estimations misfire? This would skew the impact of different bits of sensory evidence, and of different predictions. Precision estimation is the brain's way of telling itself where, and by how much, to place its bets.
When this goes wrong, our brains will bet badly; they will misestimate what to take seriously and what not to take seriously, thereby generating false or misleading experiences. This is exactly what seems to be happening with functional disorders. In these cases, unwilled misallocations of precision act as self-fulfilling prophecies.
Predictions of pain or impairment become highly overweighted, and those predictions overwhelm the actual sensory evidence, forcing experience to conform to our own hidden but misplaced expectations.
I found examples of this to be fascinating.
As I said in my first post about the book, it's going too far to say that this proves that we create our own reality. However, our brains definitely shape our experience of reality, sometimes in disturbing ways. "Functional" here means that there is a loss of function without evidence of systemic, or structural, damage of disease.
There is good evidence that misfiring precision assignments (unusual patterns of attention) play a role in many, perhaps all, functional neurological disorders. For example, simply distracting the sufferer by making them direct their attention elsewhere often makes functional (but not structural) tremors vanish.
...This creates a version of the famous "refrigerator light illusion." You might infer that your fridge light is constantly on just because the light is on every time you look inside. But actually it is the act of looking (opening the door) that turns on the light.
Similarly, you might believe you have a near-constant tremor because the tremor is always there when you pay attention to it. But if the tremor is actually in whole or in part the result of the process of "predicting and attending" itself, that assumption may be wildly wrong.
...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.
...To make sense of these self-constructed feelings of pain, numbness, weakness, or paralysis, sufferers may start to suspect deep hidden causes -- such as persistent hidden illness. These new beliefs then further reinforce the expectations of those symptoms, reinforcing the cycles of aberrant attention.
...This is rather like the case of the performer with stage fright whose true abilities are masked by their own mounting expectations of failure. The circularity is daunting. Every new instance of stage fright confirms the expectations of failure, and those expectations ensure that the instances of failure accumulate.
Recognizing this circularity is, however, often the first step in breaking the cycle, as we'll see later when looking at ways to "hack" our own predictive brains.
For lots of people, pain is an unpleasant part of their daily life. Clark speaks about pain in this chapter.
Individuals will differ in how they assign precision to bodily signals, including those associated with pain and disability. Moreover, living with a condition for a long time enables idiosyncratic expectations (for example, about severity in different contexts) to arise and become ingrained.
This means that even where there is some standard structural cause such as a bulging or herniated disc in someone with back pain, the way we experience our symptoms may over time come to involve large doses of mindset and expectation.
In a certain sense, chronic pain at that point is perhaps best considered not so much as a symptom, but as the disease itself -- the very state that needed to be addressed.
...It shows us exactly why, as leading pain theorist Mick Thacker puts it, 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.
Like all perceptions, it takes shape only thanks to the precision-weighted interaction of predictions and current bodily signals. It is that process of combination that provides the wiggle room that enables persistent pain or impairment without damage, threat, or disease.
This is not to say that everything will respond to changes in expectations. It won't. But attention and expectation are key players in the construction of all our experiences of health and illness, and this is true even when standard structural causes (damage or disease) are present.