Human Flourishing in the Age of Computational Neuroscience

Next week we are publishing a podcast conversation with Shamil Chandaria—a former advisor to Google DeepMind and a research fellow at Imperial College London Centre for Psychedelic Research and Oxford University’s Centre for Eudaimonia and Human Flourishing—on the topics of neuroscience, psychology, meditation, psychedelics, and human flourishing.

I have wanted to speak with Shamil since I watched his lecture at Oxford on computational neuroscience and meditation, The Bayesian Brain and Meditation.

Since it is probably the most technical conversation we’ve had on the podcast, I want to lay the groundwork and cover the foundational idea and related concepts to help listeners digest the discussion.

This foundational idea is a novel and counterintuitive way of understanding the human brain and subjective experience that we’ll refer to as the Predictive Brain Hypothesis.

This model challenges the traditional idea that we passively perceive the world “as it is,” proposing instead that our brains actively construct our reality through predictions and comparisons with sensory data. By understanding how our brains predict and construct our reality, we can gain greater control over our experiences and move towards a state of flourishing.

Here are the key takeaways:

• The brain is a prediction machine: It constantly generates models of the world based on past experiences and uses these models to predict incoming sensory information.

• Our perception is an active construction: Rather than passively receiving information, our brains actively shape our experiences by comparing predictions with actual sensory data.

• Prediction errors drive learning: When predictions mismatch reality, the brain updates its models, leading to learning and adaptation.

• Meditation and psychedelics can recalibrate our predictive models: These practices can help us become aware of and potentially modify our ingrained patterns of thought and perception, leading to greater well-being.

• Understanding the predictive brain can improve mental health: This framework offers new insights into conditions like depression, anxiety, and PTSD, potentially leading to more effective therapies.

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Before we get into this week’s dispatch, I want to highlight our friends at the Tiny Blue Dot Foundation (TBD), who have just announced their latest Request for Proposals for scientific studies of the Perception Box.

Tiny Blue Dot Foundation strives to help people understand that they live in their own unique Perception Box whose walls can be expanded to minimize suffering, increase acceptance of self and others, and view trauma and other challenges as opportunities for growth.

TBD has allocated $9,000,000 to fund up to 10 rigorous research projects related to The Science of the Perception Box. 

TBD ran similar RFPs over the last two years and has funded 23 projects thus far. Information about these projects can be found here and here.

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What is Experience?

The conventional way we understand our moment-to-moment experience is that we are perceiving a fixed, objective, immutable world.

It seems we experience the world as it is.

But consider the dress that broke the internet.

Is the dress above blue and black or white and gold?

In 2015, a seemingly simple photo of a dress went viral on social media, dividing the internet into two camps: those who saw it as blue and black and those who saw it as white and gold¹. 

The phenomenon highlighted how our perception of color isn't solely determined by the wavelengths of light entering our eyes but also by how our brains interpret that information based on factors like lighting conditions and our unique, idiosyncratic experience.

Our brains constantly make predictions about the world around us, including the color of objects. In the case of the dress, the ambiguous lighting in the photo caused our brains to make different assumptions about the light source, leading to different color perceptions.

The dress is perhaps the most canonical example of how perception arises from a combination of incoming sensory data and each individual’s own idiosyncratic prediction of that information.

While the incoming sensory data is unchanged, it is the unique ways in which our brains—shaped through our own unique personal experiences—anticipate and render this incoming information that creates our conscious experience.

Another popular example is the ‘checker shadow illusion’ in which two squares on a checkerboard (labeled A and B) appear to be different shades of grey but are, in fact, the same color. 

When interpreting color, our brains take into account the surrounding context, including shadows and other visual cues. In this illusion, the shadow cast by the cylinder tricks our brains into perceiving square B as lighter than square A, even though they are identical.

While these are perhaps inconsequential optical illusions that may seem to have no bearing on our personal well-being, they point to the underlying neurocomputational processes that provide novel and compelling explanations for things like depression, anxiety, and post-traumatic stress disorder, among others.

We often assume that our experience directly reflects an objective reality.

We believe we see the world “as it is.”

These illusions challenge this assumption. They demonstrate that our experience is not a passive reception of sensory information but an active construction by our brains. Our brains constantly predict what we will see, hear, and feel based on past experiences and current context. These predictions then influence our perception, shaping our moment-to-moment experience.

In other words, the brain is the organ of prediction.

The Brain is the Organ of Prediction

“Brains…are bundles of cells that support perception and action by constantly attempting to match incoming sensory inputs with top-down expectations or predictions.”

—Andy Clark

The common assumption is that the eyes operate as cameras, capturing the visual scene of the world around you; the ears as microphones that pick up sound waves moving through the air; and sensory nerves throughout the body reliably report the sense of touch, etc.

This is the view of an old paradigm that recent neuroscience and psychology research has proven not just wrong but physically impossible.

Contrary to this popular belief, the world you experience—what you see, hear, feel, etc.—is not an accurate representation of objective reality as it really is. 

Rather, your experience is more like a controlled hallucination or simulation generated by a few pounds of wet meat, mostly fat, encased in the darkness of your skull.

Yes, of course, sensory information is received and propagated through a signal-processing apparatus in the nervous system in a bottom-up manner, but this is only half the story.

It is the fact that information flows in the other direction—top-down, from higher-level brain structures in anticipation of the bottom-up sensory information—that makes the matter of experience, perception, and sensation all the more fascinating and mysterious.

This top-down flow of information, commonly referred to as the brain’s Generative Model, is precisely that, a model generated by the brain that predicts the incoming sensory data, as well as the cause and significance based on the brain's understanding of the environment, context, and prior experiences.

The interplay between bottom-up sensory information and top-down predictions is key to understanding our subjective experience. This intricate dance between the world and our minds is a captivating area of scientific inquiry. It has profound implications for therapeutic practices like psychotherapy, meditation, and psychedelic-assisted therapy, offering clues as to why these methods sometimes succeed and sometimes fail.

Top-Down Predictions, Bottom-Up Sensory Data & Prediction Errors

“...the brain is an inference machine that actively predicts and explains its sensations. Central to this hypothesis is a probabilistic model that can generate predictions, against which sensory samples are tested to update beliefs about their causes”

—Prof Karl Friston

The top-down predictions (generative model) are based on prior experience about the cause and significance of incoming sensory input and are referred to as top-down because the model is stored in “higher brain levels,” such as the cortex—the most recently evolved part of the brain responsible for complex functions like perception, prediction, and decision-making.

These top-down predictions flow down to meet the incoming sensory information traveling bottom-up from our senses. Outside of our awareness, these two streams of information are constantly compared. 

If a prediction aligns with the incoming sensory data, it reinforces the brain's existing world model. However, if there's a mismatch—a prediction error—the brain revises its model to better reflect reality.

In other words, the generative model—the simulation created by our brain—is what we experience, and it is constantly revised as it receives and processes sensory input. Our perception isn't a passive reflection of the world, but an active construction, constantly refined through this predictive process.

Importantly, this system evolved not for perfect accuracy, but for survival. The brain prioritizes predictions that help us navigate our environment and respond effectively to potential threats, even if those predictions sometimes deviate from objective reality.

The Predictive Brain, Meditation & Psychedelics

“It turns out that a really important piece of the puzzle to make a prediction machine work well is that it learns that it's a prediction machine.”

—Mark Miller

Predictive brain dynamics can serve as a powerful framework for understanding the states of consciousness associated with meditation, spiritual awakening, and psychedelic experiences.

In this lens, practices like meditation and the responsible use of psychedelics afford us opportunities to observe and recalibrate the brain’s predictive models. 

In meditation, as practitioners cultivate awareness and equanimity, the predictive models begin to loosen their grip, revealing that much of what we experience—including thoughts, emotions, and even the sense of self—is constructed.

This de-reification of mental constructs may be akin to what many spiritual traditions refer to as the process of "awakening."

“Awakening” can be seen as the recognition of the fabricated nature of the generative model.

Instead of passively accepting reality as it is, one becomes lucid within the simulation, or as Shamil puts it, becoming lucid in the matrix—not escaping the model but realizing it’s a model and thus reducing the emotional reactivity tied to it.

Psychedelics, too, can act as a catalyst for this process, especially in their ability to dissolve rigid predictive models temporarily. 

This phenomenon is closely aligned with the "REBUS model," co-developed by Shamil and Robin Carhart-Harris, which posits that psychedelics reduce the precision of top-down predictions, creating an opportunity for bottom-up sensory data to reshape one's models of reality. 

Through both meditation and psychedelics, the brain can learn to update its generative models in ways that reduce suffering and enhance human flourishing. 

By embracing the realization that much of what we experience is a construction, we gain the ability to choose which stories we believe, which emotional responses to act on, and ultimately, how we wish to live.

In summary, the predictive brain model provides a compelling framework to bridge ancient contemplative practices and cutting-edge neuroscience, offering new pathways to understand and foster human flourishing through meditation, spiritual awakening, and psychedelics.

I am looking forward to sharing my conversation with Shamil with you all next week.

1. It’s blue and black