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Neuroscience
The Brain as a Prediction Machine: The Key to the Self?
Part 2: Sense of self may arise from the brain’s predictions and simulations.
Posted January 25, 2022 Reviewed by Michelle Quirk
Key points
- Consciousness and the sense of self are inextricably interwoven with being a living organism.
- Sense of self arises partly from a feedback loop of the brain’s modeling, predicting, and controlling of the body’s internal state and actions.
- Feeling states and emotions are central to the sense of self, providing the brain with a sense of ownership of all its mental representations.
The […] intuition that the conscious self is somehow apart from the rest of nature—a really-existing immaterial inner observer looking out onto a material external world—turns out to be just one more confusion between how things seem and how they are. –Anil Seth, Being You: A New Science of Consciousness1
In Part 1 of this two-part series, we explored how theories that reconceptualize the brain as organized around forming predictions/expectations help explain many of the brain’s features and bugs and illuminate the very nature of consciousness. In Part 2, we will look at how understanding the brain as a prediction machine also sheds light on how the brain acquires a sense of self.
Consciousness is inextricably interwoven with being a living organism.
In his popular TED talk, the neuroscientist Anil Seth suggests that “Your experience of being a self, the specific experience of being you, is…a controlled hallucination generated by the brain”—a perception formed by the brain’s predictions or simulations of sensory data of specific kinds.2 “Our conscious experiences of the world around us, and of ourselves within it, happen with, through, and because of our living bodies.”3
Seth calls this the “beast machine” theory of consciousness—to emphasize the centrality of our physical, animal nature.4 He posits “bedrock layers” of selfhood “intimately tied to the interior of the body, rather than to the body as an object in the world.” These include affective experiences (emotions and moods).
Affective experiences can be understood as distinctive kinds of “controlled hallucination.” Seth suggests that the brain makes predictions or best guesses about its internal state—he calls the idea “interoceptive inference.” The term interoceptive refers to perception of sensory signals that originate from within the body, especially in the gut and other internal organs, as opposed to exteroceptive, which refers to stimuli from the external environment.
Just as the brain has no direct access to the causes of exteroceptive sensory signals like vision, which are out there in the world, it also lacks direct access to the causes of interoceptive sensory signals, which lie inside the body.…Every emotional experience is rooted in top-down perceptual best guessing about the state of the body.”5,6
The brain’s modeling and predicting of the self is intertwined with its modeling and predicting of the world.7
Self-perception is fundamentally about maintaining physiological stability (homeostasis).
In contrast to perceptual inference, which is about finding things out (about the external environment), interoceptive inference is primarily about controlling things (inside the body). “Self-perception is not about discovering what's out there in the world, or in here, in the body. It's about physiological control and regulation—it's about staying alive.”8 The brain’s predictions or best guesses about its internal state can be understood to be part of an active process by which it controls the body’s internal organs and physiological parameters. For example, the brain predicts that blood sugar should be at certain levels. If this parameter deviates from what is expected (generating a prediction error), then the brain sets in motion active measures to ensure the return to the expected range. Those measures can be physiological or behavioral (e.g., insulin secretion or obtaining food). “Interoceptive inference exemplifies active inference, in that prediction errors are minimized by acting to fulfill top-down predictions.”9
In a sense, even the simplest, most primitive organisms “care” about maintaining their stability and biological integrity, resisting degeneration. So, too, do the individual cells in complex multicellular organisms like us. Central nervous systems coordinate this effort. “This imperative for self-organization and self-preservation in living systems goes all the way down: Every cell within a body maintains its own existence just as the body as a whole does.” For this and other reasons, Seth is inclined to believe that consciousness might be substrate-dependent—it might only be possible in biological organisms.10
This drive of cells to resist degeneration is a defining feature of life: the push against entropy. The second law of thermodynamics has thus been said to be the first law of life and the first law of psychology.11
The stability of the self is an illusion.
Seth hypothesizes that since self-perception is primarily about physiological control and maintaining stability of the organism, the brain may be inclined to misperceive the self as unchanging over time:
Effective physiological regulation may depend on systematically misperceiving the body's internal state as being more stable than it really is, and as changing less than it really does. Intriguingly, this proposal may generalize to other, higher levels of selfhood.…Across every aspect of being a self, we perceive ourselves as stable over time because we perceive ourselves in order to control ourselves, not in order to know ourselves.12
So, too, for the sense of self as an entity: “the predictive machinery of perception, when directed inwardly makes it seem as though there really is a stable essence of ‘me’ at the center of everything.”13
Thus, we may have the illusion of being a “real,” stable entity that exists unchanging over time, because this is our brain’s expectation.14
The evolution of feeling.
A fundamental driver for the evolution of brains in the first place (beginning more than 500 million years ago) would have been the adaptive advantages that central nervous systems conferred in enabling more flexible, coordinated behavioral control and more sophisticated self-regulation. Perhaps even more so with the evolution of a conscious sense of self.
The neuroscientist Antonio Damasio, like Seth, focuses on the centrality of life processes and the embodied brain in the formation of conscious minds and a subjective sense of self. Damasio emphasizes the evolutionary perspective. He has developed and articulated his theory in a number of books, most recently Feeling & Knowing: Making Minds Conscious.15
Damasio argues that the key to making minds conscious is to imbue them with feelings/emotions, which are hybrid phenomena bridging body and brain, physical and mental. Feelings are firmly rooted in bodily sensations and homeostasis.
The most primitive nervous systems,16 which would have been capable of producing very simple neural representations,17 soon evolved the additional capacity to enable a primitive form of evaluation, the attachment of “valence” or value—external objects being marked as “good” or “bad” for the organism’s survival.18 This was achieved through mindless mechanistic chemical processes. Damasio formulates this as a very early form of subjective experience, an early form of “feeling.”19
Feelings operate as alerting sentinels. They inform each mind…of the state of life within the organism to which that mind belongs. Moreover, feelings give that mind an incentive to act according to the positive or negative signal of their messages….Feelings do more than provide valuable information: they force us to act according to the information. They motivate our actions.20
This is abundantly clear for the most basic types of feelings such as pain, hunger, and thirst.21
Feelings provide the brain with a sense of ownership of all its mental representations.
For Damasio, the addition of feelings to the mind’s sensory images is key to making minds conscious. Moreover, the very nature of the representation of feelings indicates that they have originated from the brain’s own body, thereby giving the mind a sense of ownership over them.
What does begin to engender consciousness is the enrichment of the mental flow with the sort of knowledge that points to the organism as the proprietor of the mind.…Ownership knowledge can be obtained from specific facts and, quite directly, from homeostatic feelings. Easily, naturally, and instantaneously, as often as needed, homeostatic feelings identify my mind with my body, unequivocally, no extra reasoning or calculation needed.”22,23
Nested self-referential internal representations.
Our brains have layered or, rather, nested internal representations of internal representations—higher, more abstract representations of lower, more concrete representations.24 The brain’s reflection on itself is recursive and self-referential, like the infinite regress of reflections of reflections obtained by holding two mirrors facing each other. The modeler contains a model of itself doing the modeling.
Predictive modeling is an important feature of the system—predicting and controlling the next internal state of the organism and its next response to a stimulus. In a very simple organism, that response may be limited to approach or withdrawal and is immediate. In humans, with all the layers of complex neuronal networks intervening between sensory receptors and motor outputs, the repertoire of behavioral responses is vastly greater and less stimulus-bound. There are far more degrees of freedom. And the response can be very delayed if necessary. There is far more computation of environmental variables in determining the response, and far greater integration of past experience (learning, memory) in shaping it. Furthermore, human actions can first be tested as mental simulations before implementation—we call this imagination and planning (other animals do it, too; we do it more). Out of all this emerges our sense of agency.
We are the sum of all our complex, dynamically interconnected brain networks. We are composed of a lifetime of remembered experiences, knowledge, learned behaviors, and habits. We are all of that information, physically embodied in the total network’s connections, recursively reflecting on itself in a cybernetic loop. We are organized matter, a dynamic network of physically encoded information.
References
1. Anil Seth, Being You: A New Science of Consciousness (New York: Dutton, 2021), p.202.
2. Seth elaborates: “There are in fact many different ways we experience being a self. There's the experience of having a body and of being a body. There are experiences of perceiving the world from a first-person point of view. There are experiences of intending to do things and of being the cause of things that happen in the world. And there are experiences of being a continuous and distinctive person over time, built from a rich set of memories and social interactions.” [Anil Seth, “Your brain hallucinates your conscious reality,” TED video transcript, filmed Apr 2017 in Vancouver, BC, https://www.ted.com/talks/anil_seth_your_brain_hallucinates_your_conscious_reality/transcript?language=en.]
3. Being You, p. 181.
[Click 'More' to view footnotes 4-24].
4. In deliberate contradistinction to the 17th century philosopher Rene Descartes, who tried to distinguish humans from soulless nonhuman animals—which Descartes referred to as “beast machines,” Seth argues that understanding our nature as living creatures is fundamental to understanding the nature and origin of our conscious experiences, and therefore calls his theory the “beast machine” theory of consciousness.
5. Being You, p.186, 188.
6. Seth explains further: “these states have to be inferred through Bayesian best guessing. As with all predictive perception, this best guessing is achieved through a brain-based process of prediction error minimization. In the context of interoception, this is called interoceptive inference. Just as with vision and with hearing—just as with all perceptual modalities—interceptive perception is a kind of controlled hallucination.” (Being You, p. 196)
7. The philosopher Albert Newen posits “two parallel hierarchies of processing, one based on prior hypotheses for the external world, and one based on prior hypotheses for the self.” (Newen A. (2018). The Embodied Self, the Pattern Theory of Self, and the Predictive Mind. Front Psychol. 9:2270. doi: 10.3389/fpsyg.2018.02270). Similar to Seth’s theory, in Newen’s model: “self-consciousness results from an integration of an embodied, basic affective flow with an intentional object (the self as agent or as center of perception, imagination or thought) where this integration remains anchored in an embodied self.” Newen elaborates: “The basis for a self is a biological system that perceives and acts in the world, and such a biological system is a self only if it develops self-representations about itself ‘as itself’, i.e., in an immediate way, not representing itself as an object but as the subject of perception and action or thinking." He adds: “Emotions essentially involve an embodied affective flow, and an affective, emotional life is a constitutive part of the self.” He sums up his detailed thesis: “The principal organization of a mechanism of building up a self-model is such that both types of representations [i.e. of the self and of the external world] are always activated and developed in parallel. Modeling oneself is a process which is always activated when one interacts with the world – much as a shadow is present when a person walks in the sun.”
Newen helpfully systematizes the characteristic features which are candidates for constituting a self:
“The self is a biological system – here a human being – which has the capacity for self-consciousness, where the latter is realized in immediate self-representations which are consciously experienced and integrated into a pattern. Such a pattern normally consists of (1) typical affective and vegetative features like homeostatic processes and a body-centered frame of reference which are the foundation for an evolutionarily basic distinction between a biological system and its environment; (2) typical behavior or behavioral dispositions like self-directed dispositions of self-care for bodily conditions and for psychological conditions (e.g., via self-deception) and for social conditions such as being a self in different groups; (3) self-directed expressive behavior like self-directed gestures, body postures and speech; (4) experienced features such as a first-person perspective, a sense of ownership of body parts, and a sense of agency over one’s actions; and (5) cognitive features such as explicitly imagining oneself or thinking about oneself and telling autobiographical stories about oneself. Furthermore, each episode of self-consciousness has (6) an intentional object, namely the self, i.e., the self-representing biological system, respectively, the human being.”
8. Being You, p.178.
9. Seth expands on this topic: “There is a useful term in physiology to describe this process: ‘allostasis.’ Allostasis means the process of achieving stability through change, as compared to the more familiar term ‘homeostasis,’ which simply means a tendency toward a state of equilibrium. We can think of interoceptive inferences being about the allostatic regulation of the physiological condition of the body.” (Being You, p. 197). Seth also relates his theory to Karl Friston’s Free Energy Principle (FEP) of living organisms (Friston, K.J., Stephan, K.E. Free-energy and the brain. Synthese. 2007;159(3):417-458. doi:10.1007/s11229-007-9237-y]. Seth explains in an interview: “The free-energy principle is not itself a theory about consciousness, but I think it’s very relevant because it provides a way of understanding how and why brains work the way they do, and it links back to the idea that consciousness and life are very tightly related. Very briefly, the idea is that to regulate things like body temperature—and, more generally, to keep the body alive—the brain uses predictive models, because to control something it’s very useful to be able to predict how it will behave. The argument I develop in my book is that all our conscious experiences arise from these predictive models which have their origin in this fundamental biological imperative to keep living.”
10. Computerized artificial intelligence might not be capable of true consciousness and a true sense of self unless perhaps if it is designed to “care” about its continued existence down to its very core. (https://www.quantamagazine.org/anil-seth-finds-consciousness-in-lifes-push-against-entropy-20210930)
11. Things in the universe tend toward increasing states of entropy or disorder, dictated by the second law of thermodynamics. Living things have “figured out” ways of resisting that natural degeneration, temporarily—for the duration of their lifetime. All living things are purpose-driven, whether or not they possess a modicum of consciousness, in that they strive to keep living and propagate themselves, and they “make an effort” toward that goal. Nonliving things make no such “effort.” Thus, when life first arose in the universe, spontaneously and unguided, purposiveness emerged. See my post Where Does Purpose Come From? (If the Universe Had None) for a summary of Terry Deacon’s cogent theory of how this might have happened: how the earliest and most primitive forms of a “self” could have arisen—a self in the sense of being a self-contained system that has some “purpose.”
This is why it has been said that the second law of thermodynamics is the first law of life—the imperative to maintain stability and resist entropy (i.e., opposing the second law of thermodynamics). [Michael Shermer, Heavens on Earth: The Scientific Search for the Afterlife, Immortality, and Utopia (New York: Henry Holt, 2018), pp. 245, 251.] Indeed, for the same reason, the second law of thermodynamics can also be said to be the first law of psychology. [Tooby, John, Leda Cosmides and H. Clark Barrett. 2003. “The second law of thermodynamics is the first law of psychology” Psychological bulletin 129 (6): 858-65.]
For further explanation of how complexity and life arose spontaneously in the universe despite the second law of thermodynamics, and an exploration of what this all means to us philosophically, see my post (and its footnotes): Life Is Short and the World Will End, Can It Have Meaning?
12. Being You, p.200.
13. Being You, p.200.
14. See also my post Is Consciousness an Illusion? which presents another theory (Attention Schema Theory, broadly compatible with the theories outlined here), to explain why consciousness feels the way it does—why it feels like a subjective inner experience, and why it feels so nonphysical.
15. Antonio Damasio, Feeling & Knowing: Making Minds Conscious (New York: Pantheon Books, 2021).
16. Evolving more than 500 million years ago.
17. In Damasio’s (and several others’) theory of consciousness, the most basic building blocks of mental activity are the neural representations or maps of the body’s external environment and of its internal state. At a basic level, these are simply sensory images of physical phenomena. In more complex brains they also include “ideas,” but these are still fundamentally built on sensory images.
18. A very primitive form of valence evolved much earlier even than that, in unicellular organisms such as bacteria, which move toward food (e.g., glucose), thus sensing it as “good” for survival, and move away from toxins—“bad” for survival.
19. Damasio elaborates: “The earliest physiological source of feelings is an integrated chemical profile of the organism’s interior. It is likely that such a molecular-level source was present in evolution prior to the appearance of nervous systems. But this is not to say that simple organisms devoid of nervous systems would have been (or are) capable of mental experiences, beginning with the experience of feelings. Feelings reflect a chemical regulatory process, the initial condition without which they could not occur, but another condition must be met, and that is a dialogue between body chemistry and the bioelectrical activity of neurons in a nervous system. Regulatory chemical molecules ignite the feeling process but cannot complete it alone.” (Feeling & Knowing, p.86)
20. Feeling & Knowing, pp. 95, 99.
21. Damasio points out certain important “peculiarities” of interoception that contribute to these feelings being so integrally visceral and powerful: “Lack of myelin insulation and lack of blood-brain barrier allow signals from the body to interact with neural signals directly. In no way can interoception be regarded as a plain perceptual representation of the body inside the nervous system. There is, rather, an extensive commingling of signals.” Feeling & Knowing, p.94.
22. Feeling & Knowing, p.157.
23. Elsewhere, Damasio elaborates: “The flow of images is not ‘conscious,’ per se, but can be rendered conscious by adding to it knowledge to the effect that the ongoing mental contents belong to a particular organism. The above transformation is first accomplished by feelings.…The critical step in the generation of consciousness, then, is the revelation, made within the mind, that the mind belongs to and is located within a specific living organism. This revelation is firstly accomplished by feeling but is complemented by (a) proprioceptive signals arising from the musculoskeletal frame, by (b) exteroceptive signals which define organism perspective in coordinate space, and by (c) recall of memorized material related to critical aspects of the organism’s history.” Damasio A. Feeling & knowing: Making minds conscious. Cogn Neurosci. 2021;12(2):65–66. doi:10.1080/17588928.2020.1846027.
24. These include, among other things, representations of our body, behaviors, proclivities, interactions with and feedback from other people, and our whole autobiographical history. Mental representations of abstract concepts are achieved by the brain creating mental representations of representations of representations (maps of maps of maps…), each higher level distilling the essence of the more concrete lower representations, the lowest of which are simply sensory images of physical phenomena.
The neuroscientist Stanislas Dehaene speculates that maybe what makes human cognition unique is "the peculiar way we explicitly formulate our ideas using nested or recursive structures of symbols"—Stanislas Dehaene, Consciousness and the Brain: Deciphering How the Brain Codes Our Thoughts (New York, NY: Viking, 2014), (p. 250).
