The Global Workspace Theory (GWT) [5, 26] conceives of consciousness as an integrative workspace featuring limited capacity and serial processing for decision making. The workspace accesses and broadcasts salient multimodal sensory information and combines it with information from memory. It supports the monitoring and reduction of uncertainty and error correction mech- anisms. It performs non-social and social imaginary simulations and appraises their outcomes. Its core function is to support planning, decision-making, and action programming. GWT has been modeled using ”toy” models of neural networks in an analogical manner in conjunction with empirical research using brain imaging [90, 25, 24]. However, GWT has not offered mathematical principles and models capable of capturing the ensemble of functions it considers for consciousness, let alone the mechanisms of their interaction. Attempts at mathematical modeling of GWT, though quite interesting, have remained rather generic and have been based on information theoretic con- cepts, with a focus on neurally relevant concepts [107]. However they have not integrated the type of geometrical perspective we see at the core of consciousness, and could not be straigthforwardly operationalized to generate simulations relating the GW, cognitive and affective processing, and behavior.
According to global workspace theory (GWT), for a content to be conscious is for it to be sustained in working memory, and so to be available to the various cognitive systems that draw on working memory. Carruthers' case for GWT centers on four conditions. Any adequate theory of phenomenal consciousness must meet all four, but the only theories to do so are GWT and the dual content theory -- the theory that Carruthers used to endorse, according to which an aptness to be the object of higher-order thought gives a state a higher-order content alongside its first-order content. GWT is theoretically simpler than the dual content theory, which settles matters in its favor. Carruthers used to think that GWT failed one of the conditions, but he has changed his mind, hence his change in position.
The four conditions:
Fineness-of-grain: we can consciously discriminate more than we can non-indexically conceptualize. (pp. 16-20, p. 89).
Ubiquity of unconscious perception: unconscious perception is widespread even in the ventral system (pp. 61-63).
Hard-problem aptness: "phenomenal consciousness can be operationalized in terms of its aptness to give rise to 'hard problem' thought experiments" (p. 19). Consciousness has to be such that there are ways of thinking about it that are apt to give rise to thoughts like "my brain states could have been the same but this might have been different" (ibid.).
All-or-nothing: our primary, first-personal concept of phenomenal consciousness is "all-or-nothing" (p. 20): it doesn't admit of degrees. "Any given mental state (in humans, at any rate) is either categorically conscious or definitely unconscious" (p. 141). This is a claim about degrees of truth, not about degrees of intensity or focus or detail. Conscious experiences can be more or less intense, focused or detailed, but if you are having an experience of any degree of intensity, focus or detail, it is true (to degree one) that you are having an experience.
Global workspace theory (GWT) is a simple cognitive architecture that has been developed to account qualitatively for a large set of matched pairs of conscious and unconscious processes. It was proposed by Bernard Baars (1988, 1997, 2002). Brain interpretations and computational simulations of GWT are the focus of current research. GWT resembles the concept of working memory, and is proposed to correspond to a "momentarily active, subjectively experienced" event in working memory (WM)—the "inner domain in which we can rehearse telephone numbers to ourselves or in which we carry on the narrative of our lives. It is usually thought to include inner speech and visual imagery." (in Baars, 1997). GWT can be explained in terms of a "theater metaphor". In the "theater of consciousness" a "spotlight of selective attention" shines a bright spot on stage. The bright spot reveals the contents of consciousness, actors moving in and out, making speeches or interacting with each other. The audience is not lit up—it is in the dark (i.e., unconscious) watching the play. Behind the scenes, also in the dark, are the director (executive processes), stage hands, script writers, scene designers and the like. They shape the visible activities in the bright spot, but are themselves invisible. Baars argues that this is distinct from the concept of the Cartesian theater, since it is not based on the implicit dualistic assumption of "someone" viewing the theater, and is not located in a single place in the mind (in Blackmore, 2005).