American neuroscientist, Princeton, contemporary

Michael Graziano

The brain controls its attention, and like any good controller it builds a model of the thing it controls. That model is simplified and a little magical: it depicts attention as an invisible inner power. When we say we are aware of something, we are reading out the model.

The view

Graziano works on how the brain controls movement and attention, and his theory of consciousness is an engineer's theory. Control theory, the mathematics of thermostats, autopilots and robot arms, has a basic lesson: a controller works better if it has a model of the thing it controls. The brain controls the body, so it builds a body schema, a simplified model of the limbs and their positions. The brain also controls attention, the process by which some signals are boosted and others suppressed. So, Graziano reasons, it should build an attention schema too.

A schema is useful because it leaves things out. The body schema tells you where your arm is, but says nothing about muscle fibres or nerve impulses. The attention schema, in the same way, tells you what you are attending to, but says nothing about competing neural signals. It depicts attention as a simple, unified thing: a kind of invisible inner presence that reaches out and takes hold of objects. That depiction is awareness. When you insist that you have a subjective, non-physical experience of the apple in front of you, you are reporting what your attention schema says.

The argument

We claim a ghostly inner awareness because the brain's model of attention describes one. After Graziano, Rethinking Consciousness (2019)

The theory is meant to be testable. If awareness is a model of attention, then awareness and attention should usually go together but sometimes come apart, as a model can drift from what it models. Experiments do find that people can attend to a stimulus without being aware of it, and that attention is controlled less well when awareness is missing. The theory also explains why we attribute awareness to other people: the same machinery that models our own attention models theirs, which is why we can tell what someone else is focused on.

Click the objects to move attention around, then switch views. The process is messy, graded and distributed. The model is clean and simple: a beam of inner light from the self to the object. Graziano notes that people across many cultures describe the mind in just these terms, as a spirit, a ghost or an energy that can reach out from the eyes. That is just what you would expect if those descriptions were readouts of a crude internal model.

Where he meets Dennett

Graziano offers something Dennett asked for but never quite supplied: a specific, mechanistic answer to the question of how the brain produces the conviction that it has ineffable experiences. It is an answer to the Hard Question. The representation of attention is for the brain's control systems, and what happens next is better control of attention, plus the claims we make about awareness. Like Dennett, Graziano thinks a machine built with an attention schema would be conscious in every sense that matters, and would insist on it as firmly as we do.

Where they part

Graziano locates consciousness in one particular model, at one particular level, and so draws a firmer line than Dennett liked between conscious and unconscious processing. Dennett was suspicious of any single "consciousness module", which can sound like a Cartesian Theatre in miniature. Graziano's reply is that the attention schema is not a stage where things are shown, but a set of data used for control. Nobody watches it.

Graziano has also been more willing than Dennett to say that awareness, as described by the schema, is "real" in a sense, as a real model with real effects. On the central question, though, they agree: there is no extra phenomenal property for the model to be accurate about.

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Further reading

• Michael S. A. Graziano, Rethinking Consciousness: A Scientific Theory of Subjective Experience (Norton, 2019): the most accessible statement.
• Michael S. A. Graziano, Consciousness and the Social Brain (Oxford, 2013): the first book-length account.
• The neuroscience of consciousness, Stanford Encyclopedia of Philosophy.