My new favorite book talks about a fascinating subject that I've read about before, but never so clearly and in so much depth as Andy Clark's The Experience Machine: How Our Minds Predict and Shape Reality.
Now, before New Age types get all excited about how the human mind creates its own reality, this definitely isn't what Clark, a professor of cognitive philosophy, is describing. But it is true that each of us fashions our view of reality to some extent in accord with our previous experiences.
Clark starts off by relating a story of how he woke up to the sound of bird noises. Except, he soon realized that his surroundings were perfectly quiet. What had happened was that his partner had gotten a smartphone app that plays a birdsong rather than a traditional alarm.
After hearing the birdsong app for several days, Clark's brain had played a trick on him. Here's how he describes the trick, followed by a summary of his book's thesis.
I now find that I quite often awake well in advance of the start of the actual alarm, already seeming to hear the faint onset of those prerecorded chirps. These are genuine auditory hallucinations, caused by my new, strong expectation of waking to the subtle sound of the birds.
There is probably nothing sinister about my proneness to this hallucination. It has long been known that hallucinations, both auditory and visual, can be quite easily induced by the right kind of training.
But these, as well as a myriad of other intriguing phenomena, are lately falling into place of signs of something much larger -- something that lies at the very heart of all human experience. The idea (the main topic of this book) is that human brains are prediction machines.
They are evolved organs that build and rebuild experiences from shifting mixtures of expectation and actual sensory evidence. According to that picture, my own unconscious predictions about what I was likely to be hearing as I awoke pulled my perceptual experience briefly in that direction, creating a short-lived hallucination that was soon corrected as more information flowed in through my senses.
That new information (signifying the lack of birdsong) generated "prediction error signals" and these -- on this occasion at least -- were all it took to bring my experience back into line with reality. The hallucination gave way to a clear experience of a silent room.
But in other cases, as we'll see, mistaken predictions can become entrenched and contact with reality (itself a complex and vexed notion) harder to achieve. Even when there are no mistakes involved, and we are seeing things "as they are," our brain's predictions are still playing a central role.
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.
This book is about those balances and an emerging science that turns much of what we thought we knew about perceiving our worlds upside down. According to that science, the brain is constantly trying to guess how things in the world (and our own body) are most likely to be, given what has been learned from previous encounters.
Everything that I see, hear, touch, and feel -- so this new science suggests -- reflects hidden wells of prediction. If the expectations are sufficiently strong, or (as in early chirps of the bird alarm) the sensory evidence sufficiently subtle, I may get things wrong, in effect overwriting parts of the real sensory information with my brain's best guess of how things ought to be.
This does not mean that successful sensing is simply a form of hallucination, though the mechanisms are related to those of hallucination. We should not downplay the importance of all that rich sensory information arriving at the eyes, ears, and other senses.
But it casts the process of seeing -- and of perceiving more generally -- in a new and different way. It casts it as a process led by our brain's best predictions: predictions that are then checked and corrected using the sensory inputs as a guide.
With the prediction machinery up and running, perception becomes a process structured not simply by incoming sensory information but by difference -- the difference between the actual sensory signals and the ones the brain was expecting to encounter.
I'll be interested to see if this is reflected in the rest of the book -- I've only finished the first chapter -- but it makes sense to me: that religious or mystical experiences occurring entirely within one's own mind, not out there in the world, are especially prone to being hallucinations resulting from strong predictions, or expectations, of what should occur.
After all, as we've seen in the above excerpt from Clark's book, what keeps the brain in close touch with reality is sensory information that corrects erroneous predictions about what ought to be perceived.
So if a religious believer is engaged in closed-eyes meditation with the expectation that their devotion will result in experiencing God, Jesus, the astral form of their guru, divine light/sound, or whatever, and their brain manifests such an experience, there's no way for that person to use error-correcting sensory information to bring "what appears to be" into closer correspondence with "what actually is."
I said closer correspondence because in one of the last pages I read this morning, Clark dispels the notion that there's any such thing as reality "as it is" -- a favorite saying of many spiritual writers that I'm pleased to see makes little sense. Here he's talking about pain and other sorts of medical symptoms, but his point applies generally.
Since all human experience is constructed from mixtures of expectation, attention, and sensory stimulation, it will never be possible to experience either the world or your own body "as it really is." Indeed, it rapidly becomes unclear what this could even mean.
Instead, there exists a deep continuity between cases where expectation and attention create symptoms (as we saw earlier) "from whole cloth" and cases where they also reflect the operation of some more standard form of disease and injury. Functional disorders simply lie at one end of this spectrum.
If you want to experience how your brain uses prior experience to predict current reality, check out these examples of sine-wave speech.
First listen to the brief SWS (sine-wave speech) audio. Probably you can't make any sense of it. Then listen to the original audio. After you hear the original, listen again to the SWS audio. If you're like me, and probably you are, now the SWS audio will be quite clear, since your brain has the experience of the original audio to predict what the SWS audio is saying.