Challenges for theories of consciousness: seeing or knowing, the missing ingredient and how to deal with panpsychism

Abstract

Significant progress has been made in the study of consciousness. Promising theories have been developed and a wealth of experimental data has been generated, both guiding us towards a better understanding of this complex phenomenon. However, new challenges have surfaced. Is visual consciousness about the seeing or the knowing that you see? Controversy about whether the conscious experience is better explained by theories that focus on phenomenal (P-consciousness) or cognitive aspects (A-consciousness) remains, and the debate seems to reach a stalemate. Can we ever resolve this? A further challenge is that many theories of consciousness seem to endorse high degrees of panpsychism-the notion that all beings or even lifeless objects have conscious experience. Should we accept this, or does it imply that these theories require further ingredients that would put a lower bound on beings or devices that have conscious experience? If so, what could these 'missing ingredients' be? These challenges are discussed, and potential solutions are offered.This article is part of the theme issue 'Perceptual consciousness and cognitive access'.

Keywords: access; consciousness; panpsychism; phenomenal; recurrent processing.

Figure 1.

Three successive stages of visual processing after stimulus presentation. The feedforward sweep proceeds within 150–200 ms, during which low- and high-level features are extracted and translated into a (potential) motor output. This stage is unconscious. Recurrent processing starts within 100 ms after stimulus presentation, at first between low-level visual areas, and then more widespread between visual cortex. Neural correlates such as V1 contextual modulation, PPI and VAN (see text) are shown. These recurrent interactions enable phenomenal (P-) consciousness of the visual stimulus: you SEE. Eventually, recurrent interactions spread through the whole brain, causing ‘global ignition’. At the neural level this is expressed in P300 responses, and the involvement of fronto-parietal areas. The result is access (A-) consciousness, the ability to cognitively manipulate the stimulus, your reaction to it, its consequences, etc.: you KNOW. (Online version in colour.)

Figure 2.

Phenomenal content is conscious in the fly, yet comparable to unconscious content in humans. The figure depicts the richness or quality of phenomenal content (calculated as PHI in IIT) on the vertical axis. In both fly and man there is a nonlinear transition in this richness, marking the transition between unconscious to conscious processing, corresponding to the transition from feedforward to recurrent processing at the neural level. At the lower end, there is a second nonlinear transition, that between dead or alive. In both species, it therefore makes sense to talk about ‘conscious’ versus ‘unconscious’. However, the content of conscious processing in the fly is comparable to unconscious processing (e.g. deep sleep) in humans. (Online version in colour.)

Figure 3.

Recurrent processing-induced network plasticity as a potential ‘missing ingredient’. A pre-stimulus network state is depicted, with varying strengths of connections. A stimulus evokes a feedforward sweep, followed by recurrent processing. Recurrent processing may then either induce changes to the strengths of connections (via long or short term, or pre- or postsynaptic plasticity; right) or not (left). Only in the case of network changes will conscious experience arise. (Online version in colour.)