ETHOS

Empirical Tests of Higher-order Theories of Consciousness

Theories of consciousness can often be categorized as either first-order (FO) or higher-order (HO). FO theories propose that consciousness is tied to the properties or strength of an FO perceptual representation (for instance, in Global Neuronal Workspace theory, consciousness depends on the global broadcasting of an FO representation across the brain). In contrast, HO theories hold that consciousness arises when an FO state becomes monitored or meta-represented by an HO representation. HO theories originated in philosophy and have since diversified into several variants that make distinct predictions. However, unlike FO theories which have been the focus of active empirical research, HO theories have received relatively little testing from neuroscience so far. This project addresses this imbalance by focusing empirical investigations on HO theories.
HO theories are often presented as a single framework when, in fact, they vary and differ in many distinct ways, just as FO theories. This project, led by Stephen Fleming (University College London) and co-directed by Axel Cleeremans (Université Libre de Bruxelles), puts the contradictory predictions of different HO theories to the test, through the process of adversarial collaboration. It focuses on two main axes of disagreement between HO theory variants.
The first axis examines to what degree HO representations are rich or sparse, where these terms refer to specific forms of brain architecture rather than perceptual experience itself. Sparse HO theories view conscious experience as jointly determined by FO and HO states, with HO states only secondarily tracking the precision, intensity or reliability of FO states. Even within sparse theories, there is disagreement as to what the HO state is coding for (for instance, whether it distinguishes perception from imagination). In contrast, rich HO theories propose that conscious experience is fully determined by HO states. In this view, HO representations are just as rich and detailed as perceptual experience itself.

The second axis of disagreement this project investigates is concerned with whether HO representations can “misrepresent” their FO targets or not and, if so, in what way. For instance, a person might have an experience of the colour green even as their FO perceptual system is signalling for red.
The possibility of misrepresentation is central to non-relational HO theories: in the event of a mismatch between FO and HO states, conscious experience should change in tandem with the HO state.
According to relational theories, however, strong misrepresentation is impossible. This is because, in this case, it is the FO state which supplies the perceptual content that the HO state merely monitors.
Each axis of disagreement between HO theories will be tested in distinct experiments using convergent methodologies from different areas of research, such as tools from psychophysics, neuroimaging, and hypnotic suggestion.
The project team follows the high standards that have been set by previous adversarial collaborations by collecting large datasets in a way that will enable replication of the results and ensure their reliability.
All experimental procedures, datasets and analysis tools developed for this project will be made freely available to other researchers, following best open science practices. In doing so, the project will lend valuable support to future research on theories of consciousness.