The Brain as a Predicting Organ & Expectation Effects
The New Science of Placebo, Nocebo and Mindsets
Introduction
This is intended as a companion piece to the recent post on the conversation between Tony Fitzgerald and my colleague
:It also builds on topics we have covered here before:
I also strongly recommend Prof. Andrew Huberman’s interview with Dr Alia Crum on the latest science of these kinds of “expectation effects”, as well as his follow up episode on “Growth Mindset”.
After watching the full interview with Tony, I bought and read the book he recommends: “The Experience Machine: How Our Minds Predict and Shape Reality” by Andy Clark [even though the title was quite off-putting for me, because I am convinced by the perspective of Dr Iain McGilchrist in his book “The Matter with Things”, that describing parts of the human being as machine-like is an overactive left-brain hemisphere way of attending, is not true, and takes us down dark paths].
Notwithstanding this gripe, the book is interesting and provides a framework for understanding that has significant explanatory power for a lot of our human experiences and behaviours. It builds on the work of Dr Lisa Feldman-Barrett, which we also looked a previously:
that is based on the idea the brain’s main role is to keep us alive.
An Anecdotal Illustration
I have a recent, personal example which I think illustrates well some of the main concepts: I recently changed the PIN number on my mobile phone. When I am running on automatic, my brain keeps predicting that the correct sequence to tap in, based on past experience of doing this thousands of times, is the old number. The error message on the screen telling me that I have entered the wrong PIN then causes a little jolt, as my brain was expecting that the phone would be unlocked by my actions, pulling me out of automatic mode into conscious awareness.
The on-screen error causes, in turn, a so-called “prediction error” in my brain: the predicted outcomes of my action did not have the expected effect. Now my brain has to resolve the difference between the erroneous prediction and the reality. My first thought is that I must have keyed the number in wrong. Then, a second later, I remember I have changed the PIN.
The occurrence of prediction errors, and their resolution, involves learning. Each time I key in the old PIN, my brain will eventually learn from the cumulative experience of getting the error message to predict this is the wrong action, and each time my brain resolves the error by keying in the new PIN, and thus things happen as expected, so this is more likely to become the default predicted action in the future.
Predictive Processing
The new “grand theory” explored in the book is called “predictive processing”.
In the author’s own words:
“predictive processing…. [is] contrary to the standard belief that our senses are a kind of passive window onto the world, what is emerging is a picture of an ever-active brain that is always striving to predict what the world might currently have offer”.
“Nothing we do or experience—if the theory is on track—is untouched by our own expectations. Instead, there is a constant give-and-take in which what we experience reflects not just what the world is currently telling us, but what we—consciously or nonconsciously—were expecting it to be telling us. One consequence of this is that we are never simply seeing what’s ‘really there,’ stripped bare of our own anticipations or insulated from our own past experiences.”
I am with the author, and with Dr McGilchrist too, that this does not mean we are living in a simulation, or reality or truth is subjective - reality and truth are out there. but that the presentation or representation of reality we get depends on the way to attend to it.
“… predictive brains are guessing machines [that m-word again, why not just say guessing organs…], proactively anticipating signals from the body and the surrounding world. That guessing is only as good as the assumptions it makes, and even a well-informed best guess will frequently miss the mark. When [this happens], the mismatch with the actual sensory signal carries crucial new information. That information (prediction error) can be used to try again—to make a better guess at how things really are. But experience still reflects the brain’s current best guessing. It is just that each new round of guessing is a little bit better informed.”
Note that sensory signals which the brain is checking its predictions against include the usual “five senses” of the external world [exteroception], internal signals from within our own body [interoception], and the senses of where our body parts are and how they are moving [proprioception].
“This challenges a once traditional picture of perception. Whereas sensory information was often considered to be the starting point of experience, the emerging science of the predictive brain suggests a rather different role. Now, the current sensory signal is used to refine and correct the process of informed guessing (the attempts at prediction) already taking place. It is now the predictions that do much of the heavy lifting. According to this new picture, experience—of the world, ourselves, and even our own bodies—is never a simple reflection of external or internal facts.”
“Incoming sensory signals help correct errors in prediction, but the predictions are in the driver’s seat now. This means that what we perceive today is deeply rooted in what we experienced yesterday, and all the days before that”.
So importantly, our predictions and expectations of the world, and hence actions in it, are the sum total of our past experiences. It is also important to note that these predictions include our motor actions and movements.
The author of the book includes several examples of optical and audio illusions to illustrate the working of the brain as a prediction organ.
Relation to McGilchrist’s Work
Readers who have been following me for some time will know I am an aficionado of Dr McGilchrist’s [mentioned above] work on the “divided brain”, as explored in his books “The Master and His Emissary” and “The Matter with Things”.
In my view, the predictive processing idea explored above is consistent with the divided brain concept, in particular that the reality/world we get depends on the type of attention we bring to bear on it, and what we expect from it. However, McGilchrist’s work extends the idea of the brain as predictive organ as the brain having two predictive organs - the left and right hemispheres, which bring different ways of attending, and give different weights to predictions vs sensory information.
In particular, it strikes me that the over-active left brain hemisphere way of attending to the world, which McGilchrist suggests is largely responsible for many of our modern ills, corresponds to the case where, when there is a prediction error, the brain always believes its own predictions and expectations over the sensory information, often in a self-delusional way. In other words, the brain believes itself over the reality. An example of this at the cultural level is the modern propensity to believe the output of mathematical models over empirical observations about the world.
On the other hand/hemisphere, a more balanced right-hemisphere way of attending to the world corresponds to the case that, when there are prediction errors, the brain is carefully weighing up its experience together with all the broad, big picture, in context, external and embodied sensory information available to it.
Applications to Trauma and Chronic Conditions
The man thrust of the conversation between Tony and Lilian is around the application of this predictive processing idea to trauma. They go in depth, and Tony presents his idea of “Trauma Zero” based on this.
Indeed, it should be obvious that if the predictive processing concept is correct, and if our interpretations of reality are largely based on past experience, and our expectations arising from this, that one way this may become maladaptive is when a very intense stressful episode in our past becomes so salient it overrides the present sensory information. This over-riding salience of predictions based on the past stressful event, in the present, re-enforces itself, and hence the prediction error is maintained.
However, healing is then also available, through appropriate therapies, by getting the brain to juxtapose its prediction with current reality, i.e. to acknowledge the error, in such a way that the brain learns and “updates” itself with the reality of the present. This process can be very quick.
It is important to say that this not only applies to the “mental” side of things, but also to the “physical” side (in reality, there is no separation between these). This includes pain and motor disorders. If the brain is expecting and predicting pain, this too can become a vicious circle, while if the brain is expecting danger and predicting the need for defensive postures based on past experiences, this can manifest as motor issues.
For those interested in further details about this application, I suggest following [subscribing to] Lilian’s substack, where she will be posting a serialization, and further analysis, of her interview with Tony:
I keep saying this,but I recommend you take PSYCH-K with Karen McKy. Thia process gives you the ability to create a whole brain state, linking left and right together. There is where the power lies. Our two hemispheres operate differently. When oth are linked together, it's a better operating system as you have alluded to.
That these honest explorations are being made gives me a great feeling of hope and joy. Imagine if we had spent the last hundred years making truthful, intuitive progress in understanding ourselves like this rather than being dictated to by profit making companies who cannot possibly have our best interests at heart because.... because money! We have been led down a path into giving up our own powers of healing. Thank you for your posts and explorations Gary.