This is Part 5 of a five-part blog series on the evolutionary origins of consciousness. I encourage you to read Part 1 first, for the overall context. Parts 2 to 5 look in a little more detail (but still necessarily in a summarized manner) at each of six books by scientists focusing on this intriguing, fundamental way of understanding consciousness. Here in Part 5, we will discuss the theories of Michael Graziano.
The evolution of attention
Graziano gives central place to attention in his theory of consciousness, and more specifically, the brain’s model of its own attention. According to Graziano:
“Consciousness arises as a solution to one of the most fundamental problems facing any nervous system: Too much information constantly flows in to be fully processed. The brain evolved increasingly sophisticated mechanisms for deeply processing a few select signals at the expense of others, and according to AST, consciousness is the ultimate result of that evolutionary sequence.”2
Selective attention began to evolve almost as long ago as the first nervous systems, in jellyfish-like animals some 600-700 million years ago (mya). Neuronal signals in neural nets would have had to compete with one another, with the strongest signals at a given moment inhibiting the other signals and causing the organism’s motor response at that moment. After the gradual evolution of centralized nervous systems in worm-like creatures (approximately 550 mya), the next big evolutionary step in the control of attention occurred in the first tiny vertebrates, which evolved about 520 mya from lancelet-like animals. They evolved a centralized controller for attention that could coordinate among all senses, located in a primitive brain area called the tectum, which is present in all vertebrates today. It orients and coordinates attention, and directs gaze—such as when a frog tracks the movement of a fly before darting out its tongue to catch it.
The tectum constructs an internal model—a simulation that keeps track of the current state of the eyes, head, and other major body parts, making predictions about how these body parts will move next and about the consequences of their movement. With the evolution of reptiles around 350 to 300 mya, a new brain structure began to emerge, the predecessor of what later in mammals became the massively expanded cerebral cortex (mammals first evolved as tiny shrew-size creatures living in the shadows of the dinosaurs around 200 mya). The cortex is like an upgraded tectum.3
The cortex enables “covert attention”—the focusing of attention on something without having to look directly at it. In humans, this can be quite complex—we can focus our attention on memories, plans and abstract concepts.
“The cortex needs to control that virtual movement, and therefore like any efficient controller it needs an internal model. Unlike the tectum, which models concrete objects like the eyes and the head, the cortex must model something much more abstract. According to the AST, it does so by constructing an attention schema—a constantly updated set of information that describes what covert attention is doing moment-by-moment and what its consequences are.”2
The brain’s simplified model of its own attentional system
Graziano proposes that in order for more complex animals to monitor and control their specialized attention processes, the brain evolved a simplified model. The model is a schema, an internal representation, a map of sorts, much like the brain’s schema of the body it is housed in. The schema is a “cartoonish” (i.e. simplified, caricature-like) self-description depicting an internal essence with a capacity for knowledge and experience.
The schema lacks physical details of its own functioning. It has no access to its own underlying neuronal workings—the billions of neurons and synapses and electrochemical signals. The schema has no need for such details—just as a self-driving car needs only a high-level internal model of itself—such as its shape and size and how it handles the road. It would be irrelevant and a waste of processing capacity for that model to include all the more specific material details and engineering machinations of the car. So too, the information in the brain’s schema of itself portrays an imperfect, simplified, abstracted version of attention. This leads the brain to conclude that it has a nonphysical essence of awareness, and that's why people believe consciousness is nonphysical, according to Graziano—because it lacks a more detailed schema of its own machinations.4
Graziano suggests that the brain’s Attention Schema was also recruited by evolution to enable the individual to model the attention of other individuals. This would have been particularly adaptive for advanced social animals such as primates, especially humans.5 Therefore, it can be said of the Attention Schema:
“It is an ancient, highly simplified, internal model, honed by evolution to serve two main useful functions […] Its first function may have been as a self-model, to monitor, make predictions about, and help control one’s own attention. The second function may have been as a catalyst for social cognition, allowing us to model the attentional states of others and thus predict their behavior.” (Rethinking Consciousness p.64)
The additional missing ingredient for more established theories of attention and consciousness
Attention Schema Theory answers a key question that is not addressed by the other major theories of consciousness, such as Higher-Order Theory (HOT) (discussed in Part 3) and the Global Workspace Theory (GWT): namely, why consciousness feels the way it does—why it feels like a subjective inner experience, and why it feels so nonphysical. Attention Schema Theory builds on GWT, adding the extra component of a system in the brain that can model itself, monitor what it's doing and build a self-description. The attention schema is the brain’s imperfect but efficient understanding of its own attention processes.6
The illusion of consciousness as a nonphysical essence
Graziano’s theory, like Dennett’s (see Part 4), regards consciousness as an illusion—the brain believes/“insists” that it is conscious in some kind of nonphysical way, because all it knows is its simplified (“cartoonish”) nonphysical schema of its attention processes. But Graziano is careful to qualify that by calling it an illusion he does not mean that consciousness is not a real phenomenon, or that the things we are conscious of are not really “there.”7 It’s just that consciousness is not what it seems—not what we think it is:
“In the attention schema theory, consciousness is […] a simplified, imperfect account of something real. […] Every internal model is a simplified version of reality, because reality has far more complexity and microscopic texture than the brain has any reason or ability to handle. […] The brain claims to have consciousness on the basis of imperfect information.” (pp. 99-100)
“So at the heart of it all is this realization that really the study of consciousness is not the study of how a nonphysical magic emerges from the brain, but instead the study of how a machine computes information about itself and how a brain thinks it is conscious.”8
In conclusion: take-away points from this five-part series
- Theories of consciousness need to be firmly rooted in evolutionary biology.
- The brain gradually evolved to its present state of complexity, driven by the powerful sculpting forces of natural selection.
- Primitive animals might have an elementary form of consciousness with only raw, nonreflective experience (primary sensory or primary consciousness).
- Consciousness evolved gradually in complexity, as a function of more complex brains.
- Internal representations play a central role in consciousness. The brain forms representations of the external world, of its own body, and of its own attentional processes. The formation of internal representations in nervous systems is a physical process.
- Primitive organisms evolved systems for the attachment of positive or negative valence to an experience. This later formed the basis for the evolution of emotions. This too is a physical, mechanistic process.
- Emotion plays a central role in consciousness. There are competing theories of the relationship between emotions and feelings, and whether feelings are dependent on higher cognitive functions.
- Primitive self-representations evolved early, having their origin in the organism’s mapping of its own body and behavior.
- Higher, more complex regions of the brain form representations of the representations of the representations (etc.) that are formed in lower, sensory regions of the brain, with increasing levels of abstraction.
- In humans, the sense of self has a much more developed autobiographical component.
- Subjectivity is built into the very nature of life: as soon as the first cell evolved there was an inside and an outside, and therefore the beginnings of a subjective-objective divide between the body and the outside world. Subjective experience is inaccessible to external observers.
- There are differing expert opinions on whether consciousness is an illusion, or to what degree. These differences hinge partly on definitions.
- Attention, and the brain’s internal model or schema of its attentional processes, plays a central role in consciousness, and may explain why people believe consciousness is nonphysical.
- Language and cultural evolution have played central roles in the elaboration of human consciousness.
Of course, we are still far from a complete understanding of how the brain generates consciousness, but we are much further along in developing plausible and intriguing models than most people realize. There are a number of other compelling models of consciousness that have not been discussed here. This blog series has focused on evolutionary theories of consciousness, and the discussion here has only been a bare-bones summary of those theories.
Nothing in biology makes sense except in the light of evolution. Consciousness is no exception—it seems nonphysical, but is very much a biological phenomenon.
1. Michael S. A. Graziano, Rethinking Consciousness: A Scientific Theory of Subjective Experience (New York: W.W. Norton & Company, 2019).
2. Michael Graziano, “A New Theory Explains How Consciousness Evolved,” Atlantic, June 6, 2016, https://www.theatlantic.com/science/archive/2016/06/how-consciousness-evolved/485558/
3. Graziano explains: “We still have a tectum buried under the cortex and it performs the same functions as in fish and amphibians. If you hear a sudden sound or see a movement in the corner of your eye, your tectum directs your gaze toward it quickly and accurately. The cortex also takes in sensory signals and coordinates movement, but it has a more flexible repertoire.” (Graziano, Atlantic, June 6, 2016).
[CLICK 'MORE' TO VIEW FOOTNOTES 4-8]
4. This is what Feinberg and Mallatt, reviewed in Part 2, refer to as auto-irreducibility. Dennett, reviewed in Part 4, makes a similar argument to Graziano—that we only have access to a highly edited, simplified version of the net results of our underlying brain processes.
5. He ties in two other well-established concepts in social psychology, what are referred to as Theory of Mind (the ability to attribute mental states to oneself and to others), and Hyperactive Agency Detection (the tendency of humans to over-ascribe events in the environment to intentional agents).
6. GWT is a theory originally developed by Bernard Baars and further developed by Stanislas Dehaene and colleagues into a global neuronal workspace theory. According to the theory, only one piece of information at a time can gain access to a "global neuronal workspace:" Neuronal signals compete with each other constantly. When one set of signals (for example, visual processing of a particular object, such as an apple) becomes enhanced and boosted, out-competing other signals, then it becomes strong enough to influence widespread networks around the brain (this is referred to as “ignition”). In that moment, that particular set of signals (containing features of the apple) dominates the brain’s processing such that it becomes the focus of the brain’s conscious attention.
Graziano’s argument is that while GWT or neuronal workspace theory can explain very well how we attend to a particular object such as an apple, the theory on its own doesn't explain why we claim to have a subjective inner experience of the apple. He argues that the addition of AST provides the extra ingredient that explains our subjective experience of our conscious attention.
7. In a mostly favorable review of Graziano’s book, consciousness expert Sue Blackmore writes:
“I have really enjoyed Graziano’s ideas but I wish he had more warmly welcomed the fact that the AST is a form of illusionism. Instead, having briefly admitted as much, he distances himself from the idea because ‘calling consciousness an illusion is the kiss of death for a theory’ (p 97). Admittedly illusionism is hard to understand and difficult to accept. But is that a reason to disguise it? If we think consciousness is an illusion, as I do (Blackmore, 2016), we should be bold in saying so and then help people to understand it. The AST not only claims that people are wrong about their own experience but explains how and why they are wrong. This is what illusionism is and I am sorry Graziano was not more positive about it.” [Blackmore, S. Book Review: Rethinking Consciousness: A Scientific Theory of Subjective Experience. The Journal of Consciousness Studies. 2020; 27 (1-2): 242-47.]
8. Michael Graziano in an Interview on Brain Science Podcast with Ginger Campbell, M.D. October 25, 2019. https://brainsciencepodcast.com/bsp/2019/162-graziano