From a Photon to Experience

Where does conscious experience actually begin?

The original article was posted on Medium.

Imagine your friend Michael standing in front of you. You can see his face. You know it is his face because you recognise him. You might be feeling an emotion (are you happy to see him? Are you mad he hasn't called in a while?). Or perhaps you are about to say hello. This is one of the most ordinary moments a human being can have. We have all had it many times today.

And yet, if I ask you to specify the moment when your conscious experience of seeing Michael begins, you might find it surprisingly difficult.

Is it the moment you become aware that you are seeing him? But by then, you have already been seeing him but you become aware of it a little later. According to research, there is a delay of a few hundred milliseconds between neural processing and reported awareness (Dehaene, 2014; Koch, 2019).

Is it before that then? At the moment your brain has finished assembling the image? But when does it actually finish assembling the image?

Or is it earlier still, when the brain starts assembling the image? And what exactly does it mean for the brain to start? Does it start when the first signal reaches the optic nerve? Or when light hits the retina?

Different schools of thought describe consciousness in different ways. Integrated Information Theory says consciousness is the integrated structure of information itself; awareness emerges when processing achieves a certain kind of unity. Global Workspace Theory says consciousness is what happens when information becomes globally available across the brain's many specialised modules; awareness is the broadcast, not a separate event. Higher-Order Theories say awareness is a representation about representation — the brain modelling its own processing to itself. Predictive Processing says consciousness is the brain's best current model of the world, generated through prediction and correction. Enactive and embodied approaches say consciousness is not in the brain at all, but in the living organism's active engagement with its environment.

These positions disagree about much. But on one thing they tend to agree: awareness is not something separate from processing, added on top of it like a label. Awareness is part of what processing is — one of its aspects, or one of its phases, depending on whom you ask.

If that is so, then the question of when conscious seeing begins is not really a question about when, on top of processing, awareness also happens. It is a question about when processing itself begins. And that turns out to be a much stranger question than it first appears.

The Process Behind Seeing

So let us start with the part that is clear. You become aware of seeing Michael after having processed the visual input. But what does it mean that you have processed it?

Presumably, it means that signals arrived at the visual cortex, were integrated with memory, with emotion, with recognition. The brain assembled something — an image, a face, Michael's face. Is this where seeing Michael started?

Let us go further — how did those signals get to the brain in the first place? They came through the optic nerve. So it was not only the brain that did the processing; the optic nerve was already carrying something that had been processed enough to travel. The nerve doesn't lead to a door that it needs to open in order to pass on the signal to the brain. It's an integral part of the processing.

How did the signal get to the optic nerve? It came from cells in the retina, where molecules of rhodopsin absorbed photons and changed their shape, triggering a cascade of chemical reactions that became the electrical signal. So the retina was processing too. The molecule was processing. Is that where seeing started?

And how about when the photon hits your retina? Because this is where it becomes really interesting.

What Is a Photon, Actually?

A photon is not a tiny ball that flew from Michael's face, hit your retina, and dissolved into it. A photon is an excitation of the electromagnetic field — a particular shape the field takes for a particular while. A field that is present everywhere, all the time, and you, Michael, me — simply everything is immersed in it. The photon is a particular configuration the field took on its way from Michael, through the space between you, into you.

Imagine you are swimming in the sea. A wave is coming toward you. When it reaches you, if you open your mouth and swallow some of the water, the water passes through your body. It is broken down, integrated, distributed; it becomes part of your blood, your cells, your tissue. You would not say the water is still in you in the form it arrived. But you would also not say the water is gone. It has become part of you.

Something similar happens with the photon. When it is absorbed by a molecule of rhodopsin in your retina, it does not remain a photon inside you. It doesn't disappear but the potential it carried is now expressed in the molecule changing its shape. The change triggers a cascade. The cascade becomes an electrical signal. The signal travels through the optic nerve, becomes patterns in the visual cortex, integrates with memory, with recognition. The photon, like the water, has been processed — and through that processing, it has become part of you.

But something else is happening at the same moment, on the other side of the absorption process. Just like when you swallow part of the water from the wave, the sea changes. Minimally, almost imperceptibly, but it does. And the same happens with the electromagnetic field when the photon is absorbed in your retina. It changes. Seeing Michael is not just something that happened in you. It is a change in what is between you, and around you, and through you both.

Where, Then, Does Seeing Begin?

We started with a simple question: when does your conscious experience of seeing Michael begin? We tried to find a moment — the moment you become aware, the moment your brain assembled the image, the moment the signal reached the cortex, the moment the photon hit your retina. At every step, the moment moved earlier. And once we reached the photon, the moment stopped being a moment at all — it became a configuration of the field you and Michael share.

So where, then, does seeing Michael begin? Perhaps the question, asked this way, does not have the kind of answer we were expecting. Most schools of thought tell us that awareness is part of processing, not separate from it. But processing, when we follow it carefully, does not start anywhere in particular. It happens at every level at once — in your brain, in your nerve, in your retina, in the molecule, in the photon, in the field — not as a chain where one step triggers the next, but as a process that shapes what you perceive as experience while reshaping all of you and everything around you.

References

Dehaene, S. (2014). Consciousness and the brain: Deciphering how the brain codes our thoughts. Viking.

Koch, C. (2019). The feeling of life itself: Why consciousness is widespread but can't be computed. MIT Press.