Integration information theories posit that the integration of information is necessary and/or sufficient for consciousness. In this paper, we focus on three of the most prominent information integration theories: Information Integration Theory (IIT), Global Workspace Theory (GWT), and Attended Intermediate-Level Theory (AIR). We begin by explicating each theory and key concepts they utilize (e.g., information, integration, etc.). We then argue that the current evidence indicates that the integration of information (as specified by each of the theories) is neither necessary nor sufficient for consciousness. Unlike GWT and AIR, IIT maintains that conscious experience is both necessary and sufficient for consciousness. We present empirical evidence indicating that simple features are experienced in the absence of feature integration and argue that it challenges IIT’s necessity claim. In addition, we challenge IIT’s sufficiency claim by presenting evidence from hemineglect cases and amodal completion indicating that contents may be integrated and yet fail to give rise to subjective experience. Moreover, we present empirical evidence from subjects with frontal lesions who are unable to carry out simple instructions (despite appearing to understand their meaning) and argue that they are irreconcilable with GWT. Lastly, we argue that empirical evidence indicating that patients with visual agnosia fail to identify objects they report being conscious of present a challenge to AIR’s necessity claim.
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A theory of consciousness should be able to explain the neural substrates of mental states and their behavioral manifestations.
Bayne (2018) argues that the phenomenological axioms posited by ITT fail to capture the essential features of every experience.
ITT’s postulates identify an experience with the set of all mechanisms (i.e., the “conceptual structure”) and the maximally irreducible probability distribution of potential past and future states of a system as informed by a mechanism in its current state (i.e., its “cause–effect repertoire. See Tononi and Koch 2015).
But why, one might ask, is there more information contained in the representation of a blue square at some location L1, than there is in the representation of a color at L1 and a shape at L1? Why wouldn’t the first representation be reducible to its parts? The reason for this seems to be that the former representation carries the information that the color and the shape are properties of a single object (and thus their fates are non-accidentally correlated), whereas the latter representation lacks this information.
IIT’s contention that the experience of a blue square has its integrated content essentially is closely tied to the unity of consciousness: conscious unity can be understood in terms of the irreducibility of its components (see Bayne and Chalmers 2003).
For arguments against this and other claims pertaining to the axioms see Bayne (2018).
One might wonder how IIT would account for experiences in different sensory modalities that pick out the same feature of a given object. Consider, for example, the case of seeing and holding a ball. The visual and tactile experiences of the ball’s spherical shape have different phenomenal characters. How would IIT account for this difference in phenomenology, given that both experiences pick out a spherical shape? One way for IIT to accommodate this sort of phenomenal difference is to take the shared feature to be integrated differently in the different sensory modalities or submodalities. For example, the sphericality of the ball may be taken to be integrated in a visual way in one case but in a tactile way in the other (for a similar solution to the general problem, sometimes referred to as ‘Molyneux’s question’, see Chalmers 2004).
The global workspace cannot be associated with a fixed set of brain areas because various cortical areas can contain workspace neurons with suitable long-distance and widespread connectivity needed to give rise to conscious experiences. However, the fact that workspace neurons seem to be denser in certain areas such as the prefrontal cortices (PFC) and the anterior cingulate (AC) suggests that these areas play a dominant role in the function of the global workspace.
Block (1995, p. 234) argues that there is a natural use of ‘consciousness’ and ‘awareness’ corresponding to ‘access consciousness’ and ‘phenomenal consciousness’, respectively. According to Block, phenomenal consciousness can be understood as awareness, whereas access consciousness is better understood as consciousness proper. When a content is both P- and A-conscious, Block suggests that we speak of ‘conscious awareness’.
Many of those who agree that there is a meaningful distinction to be drawn between phenomenal and access consciousness argue that the two do not actually come apart. David Chalmers (1997), for example, argues that while phenomenal consciousness and access consciousness, as defined by Block (1995), coincide (i.e., are both present or both absent in the actual world), it is conceivable and, therefore, possible that they come apart. His view supports those like Baars and Prinz who take P-consciousness and A-consciousness to coincide.
In the case of vision, the intermediate level is anatomically located in a family of areas involved in processing color (hue), motion and three-dimensional shape (extra-striate brain regions). By comparison, the lower level is anatomically located in primary visual cortex (V1) and some subcortical structures such as the visual nuclei of the thalamus and the superior colliculus; the high level recruits structures in inferior temporal areas (such as TE, TEO, and sections of the superior temporal sulcus), the lateral occipital complex, and some structures in parietal cortex (such as the ventral and posterior inter-parietal areas).
Note that, on this view, high-level representations are used to mediate encoding once an attended item has been selected for use in cognitive tasks or for retention in long-term memory, but Prinz argues, high-level representations are not themselves modulated by attention and therefore do not themselves reach conscious awareness (Prinz 2012).
We are grateful to an anonymous reviewer for suggesting these objections.
As an anonymous reviewer noted, proponents of IIT could insist that these subjective reports should not be taken at face value because the Φ is maximal at posterior parts of the brain. Since the frontal activity associated with reportability is not part of the neural correlates of consciousness, reportability is suspect as a guide to the phenomenology of experience. However, this objection seems misguided. Our claim is not that reportability is part of conscious experience but rather that conscious experience is, in the good cases, accurately reportable. If IIT rejects this claim, then it is unclear what sort of evidence it can provide (apart from reportability) for the claim that its axioms govern the phenomenology of experience. If proponents of IIT claim instead that the Treisman cases are not “good” for whatever reason, but that report does generally serve as a guide to phenomenology (especially when it comes to their axioms), then the latter claim, given the disassociation between frontal activity and consciousness, starts seeming exceedingly mysterious.
While objective measures typically involve asking subjects to make forced-choice guesses about what they have seen, subjective measures typically involve reportability (Szczepanowski and Pessoa 2007; Kunimoto et al. 2001). When subjects are asked to report on whether they saw a stimulus, negative responses are taken as evidence that the stimulus was not experienced consciously.
See the special journal issue published in Consciousness and Cognition, 2015 Mar. volume 32. Edited by Robert Foley and Bob Kentridge.
We are grateful to an anonymous reviewer for raising this objection.
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Brogaard, B., Chomanski, B. & Gatzia, D.E. Consciousness and information integration. Synthese 198 (Suppl 3), 763–792 (2021). https://doi.org/10.1007/s11229-020-02613-3
- Amodal completion
- Attended intermediate-level representation theory
- Feature integration
- Global workspace theory
- Illusory contours
- Information integration theory
- Spatial neglect
- Visual agnosia