Global Workspace Theory and its associated Theater Metaphor are empirically plausible, but why should it result in consciousness? Why should globally available information being processed by separate cognitive modules make us talk about being conscious?
Sure, that's how brains see stuff, but why would that make us think that it's happening to anyone? What in the world corresponds to a self?
So far, I've only encountered two threads of thought that try to approach this problem: the Social Cognitive Interface of Kurzban, and the Self-Model theories like those of Metzinger and Damasio.
I’ll be talking about the latter, starting off with what self-models are, and a bit about how they’re constructed. Then I’ll say what a self-model theory is.
Humans as Informational Processing Systems
Questions: What exactly is there for things to happen to? What can perceive things?
Well, bodies exist, and stuff can to happen to them. So let's start there.
Humans have bodies which include informational processing systems called brains. Our brains are causally entangled with the outside world, and are capable of mapping it. Sensory inputs are transformed into neural representations which can then be used in performing adaptive responses to the environment.
In addition to receiving sensory input from our eyes, ears, nose, tongue, skin, etc, we get sensory input about the pH level of our blood, various hormone concentrations, etc. We map not only things about the outside world, but things about our own bodies. Our brain's models of our bodies also include things like limb position.
From the third person, brains are capable of representing the bodies that they're attached to. Humans are information processing systems which, in the process of interacting with the environment, maintain a representation of themselves used by the system for the purposes of the system.
Answers: We exist. We can perceive things. What we see as being our "self" is our brain's representation of ourselves. Generalizably, a "self" is a product of a system representing itself.
Note: I don't mean to assert that human self-modeling accomplished by a single neurological system or module, but I do mean to say that there are a nonzero set of systems which, when taken together, can be elegantly expressed as being part of a self-model which presents information about a person to the person's brain.
Bodily Self Models
Human self-models seem to normally be based on sensory input, but can be separated from it. Your bodily self-model looks a lot like this:
Freaky stuff happens when a body model and sensory inputs don't coincide. Apotemnophilia is a disorder where people want to amputate one of their otherwise healthy limbs, complaining that their body is "overcomplete", or that the limb is "intrusive". They also have very specific and consistent specifications for the amputation that they want, suggesting that the desire comes from a stable trait rather than say, attention seeking. They don't want want to get an amputation, they want a particular amputation. Which sounds pretty strange.
This is distinct from somatoparaphrenia, where a patient denies that a limb is theirs but is fairly apathetic towards it. Somatoparaphrenia is caused by damage to both S1 and the superior parietal lobule, leading to a limb which isn't represented in the self-model, that they don't get sensory input from. Hence, its not theirs and its just sorta hanging out there, but its not particularly distressing or creepy. Apotemnophilia can be described as lacking a limb in the self-model, but continuing to get input from it. Imagine if you felt a bunch of armness coming into your back.
In some sense, your brain also marks this model of the body as being you. I'll talk more about it in another article, but for now just notice that that's important. It's useful to know that our body is in fact ours for planning purposes, etc.
Self Models and Global Availability
Anosognosia is the disorder where someone has a disability, but is unable/unwilling to believe that they have that disability. They insist that they don't move paralyzed arms because they don't want to, or that they can actually see while they're stumbling around bumping into things.
This is also naturally explained in terms of self-model theory. A blind person with anosognosia isn't able to see, and doesn't receive visual information, but they still represent themselves as seeing. So when you ask them about it, or they try and plan, they assert that they can still see. When the brain damage leading to blindness and anosognosia occurs, they stop being able to see, but their self-model isn't updated to reflect that.
Blindsight is the reverse case where someone is able to see, but don't represent themselves as seeing.
In both cases, the person's lack of an ability to represent themselves as having particular properties interferes with those properties being referred to by other cognitive modules such as those of speech or planning.
Self-Model Theories of Consciousness
Self-Model Theories hold that we're self aware because we're able to pay attention to ourselves in the same way that we pay attention to other things. You map yourself based on sensory inputs the same way that you map other things, and identify your model as being you.
We think that things are happening to someone because we're able to notice that things are happening to something
That's true of lots of animals though. What makes humans more conscious?
Humans are better at incorporating further processing based on the self-model into the self-model. Animals form representations of and act in the environment, but humans can talk about their representations. Animals represent things, but they don't represent their representation. The lights are on, and somebody's home, but they don't know they're home.
To be continued...
Kurzban, R., & Aktipis, C. A. (2007). Modularity and the social mind: are psychologists too self-ish? Personality and social psychology review : an official journal of the Society for Personality and Social Psychology, Inc, 11(2), 131-49. doi:10.1177/1088868306294906
Ramachandran, V. S., Brang, D., McGeoch, P. D., & Rosar, W. (2009). Sexual and food preference in apotemnophilia and anorexia: interactions between “beliefs” and “needs” regulated by two-way connections between body image and limbic structures. Perception, 38(5), 775-777. doi:10.1068/p6350