Lately I’ve been reading up on global workspace theory (GWT). In a survey published last year, among general consciousness enthusiasts, integrated information theory (IIT) was the most popular theory, followed closely by GWT. However, among active consciousness researchers, GWT was seen as the most promising by far (although no theory garnered a majority). Since seeing those results, I’ve been curious about why.
One reason might be that GWT has been around a long time, having first been proposed by Bernard Baars in 1988, with periodic updates all recently republished in his new book. It’s received a lot of development and has spawned numerous variants. Daniel Dennett’s multiple drafts model is one. But perhaps the one with the most current support is Stanislas Dehaene’s global neuronal workspace, which I read and wrote about earlier this year.
All of the variants posit that for an item to make it into consciousness, it has to enter a global workspace in the brain. This is most commonly described using a theater metaphor.
Imagine a play in progress in a theater. A light shines down on the stage on the currently most relevant actor or events, the light of conscious. The backstage personnel enabling the play, along with the director and other controlling personnel, are not in the light. They’re in the unconscious dark. The audience, likewise, is in the dark. That is, the audience members are unconscious information processing modules.
This last point is crucial, because this is not the infamous Cartesian theater, with an audience of one conscious homunculus, a little person observing events. Such a notion merely defers the explanation. If the homunculus provides consciousness, then does it too have its own homunculus? And that one yet its own? With infinite regression? By stipulating that the audience is not conscious, we avoid this circular trap.
That said, one issue I have with this metaphor is the passivity of the audience. Consider instead a large meeting room with a lot of rowdy people. There is someone chairing the meeting, but their control is tenuous, with lots of people attempting to talk. Every so often, someone manages to gain the floor and make a speech, conveying their message throughout the room. At least until the next person, or coalition of people, either adds to their message, or shouts them down and takes over the floor.
Most of the talking in the room is taking place in low level side conversations. But the general room “consciousness”, that is, the common things everyone is aware of, are only of what’s conveyed in the speeches, even though all the side conversations are constantly changing the tenor and state of people’s opinions throughout the room, and could effect future speeches.
I think this alternate metaphor makes it more clear what it means to enter the workspace. In all of the theories, the workspace is not a particular location in the brain. To “enter” it is to be broadcast throughout the brain, or at least the cortical-thalamic system.
How does a piece of information, or a coalition of information, accomplish this? There is a competition. Various modules in the brain attempt to propagate their signals. In many cases, actually in most cases, they are able to connect up to one or a few other modules and accomplish a task (the side conversations). If they do, the processing involved is unconscious.
But in some cases, the signal from a particular module resonates with information from other modules, and a coalition is formed, which results in the information dominating one of the major integration hubs in the brain and brings the competition to the next level.
At some point, a signal succeeds in dominating the frontoparietal network, all competing signals are massively inhibited, and the winning signal is broadcast throughout the cortical-thalamic system, with binding recurrent connections forming circuits between the originating and receiving regions . The signal achieves what Daniel Dennett calls “fame in the brain”. It is made available to all the unconscious specialty modules.
Many of these modules will respond with their own information, which again might be used by one or more other modules unconsciously. Or the new information might excite enough other modules to win the competition and be the next broadcast throughout the workspace. The stream of consciousness is the series of images, concepts, feelings, or impulses that win the competition.
One question that has long concerned me about GWT: why does simply being in the workspace cause something to be conscious? I think the answer is it’s the audience that collectively makes it so.
Consider Dennett’s “fame in the brain” metaphor. If you were to meet a famous person, would you find anything about the person, in an of themselves, that indicated fame? They might be attractive, an athlete, funny, or extraordinary in some other fashion, but in all cases you could meet non-famous people with those same traits. What then gives them the quality of fame? The fact that large numbers of other people know who they are. Fame isn’t something they exude. It’s a quality they are granted by large numbers of people, which often give the famous person causal influence in society.
Similarly, there’s nothing about a piece of information in the brain, in and of itself, that makes it either conscious or unconscious. It becomes a piece of conscious content when it is accessible by several systems throughout the brain, memory systems that might flag it for long term retention, affect systems that might provide valenced reactions, action systems that might use it in planning, or introspective and language systems that might use it for self report. All of these systems end up giving the information far more causal influence than it would have had if it remained isolated and unconscious.
Admittedly, this is a description of access consciousness. Someone might ask how this implies phenomenal consciousness. GWT proponents tend to dismiss the philosophical idea that phenomenal consciousness is something separate and apart from access. I agree with them. To me, phenomenal consciousness is what access consciousness is like from the inside.
But I realize many people don’t see it that way. I suspect many might accept GWT but feel the need to supplement it with additional philosophy to address the phenomenal issue. Peter Carruthers, in his latest book, attempts to philosophically demonstrate how GWT explains phenomenal experience, but since he’s a “qualia irrealist”, I’m not sure many people seeking that kind of explanation will find his persuasive.
There are a lot of nuanced differences between the various global workspace theories. For example, Baars most often speaks of the workspace as being the entire cortical-thalamic core. Dehaene tends to emphasize the role of the prefrontal cortex, although he admits that parietal, temporal, and other regions in the frontoparietal network are major players.
Baars emphasizes that processing in any one region of the cortical-thalamic core can be conscious or unconscious. Any region can potentially win the competition and get its contents into the workspace.
Dehaene is more reserved, noting that some regions, particularly executive ones, have more connectivity than others, and that very early sensory regions don’t necessarily seem capable of generating workspace content, except indirectly through later sensory layers.
Both agree that subcortical regions generally can’t contribute directly to the workspace. Although Baars sees the hippocampus as a possible exception.
Both Dehaene and Baars think it’s likely that many other animal species have global workspaces and are therefore conscious. Baars seems confident that any animal with a cortex or a pallium has a workspace, which I think would include all vertebrates. Dehaene is again a bit more cautious, but he sees all mammals as likely having a workspace, and possibly birds. Peter Carruthers, who converted from his own particular higher order theory to GWT, doesn’t think there’s a fact of the matter on animal consciousness.
A common criticism of GWTs is that they are theories of cognition rather than consciousness. Since to me, any scientific theory of consciousness is going to be a cognitive one, I don’t see that as a drawback. And I realized while reading about them that they also function as theories of general intelligence, the holy grail of AI research. Which fits since GWT actually has origins in AI research.
GWTs also seem able to account for situations where large parts of the cortex are injured or destroyed. Unlike higher order theories (HOT), most of which seem dependent on the prefrontal cortex, if large parts of the frontal regions were lost, the workspace would be dramatically reduced but not eliminated. Capabilities would be lost, but consciousness would still exist in a reduced form.
I also now understand why the overview paper earlier this year on HOT classified GWTs as first order theories, since first order representations can win the workspace competition as well as higher order or executive ones. This allows GWTs to avoid many of the computational redundancies implicit in HOT, redundancies that might seem unlikely from an evolutionary perspective.
And I’ve recently realized that GWT resonates with my own intuition from reading cognitive neuroscience, which I described in a post a while back, that subjective experience is communication between the sensory, affective, and planning regions of the brain. The broadcasting workspace seems like the medium of that communication.
GWTs are scientific theories, so they’ll either succeed or fall on empirical research. I was impressed with the wealth of empirical data discussed in Dehaene’s and Baars’ books. Only time will tell, but I now understand why so many consciousness experts are in this camp.
What do you think? Does this theory sound promising? Or do you see problems with it? What stands out to you as either its strengths or weaknesses?