I have examined the defining characteristics of conscious versus unconscious vision. Incremental grouping and segregation according to Gestalt laws seems to be a defining characteristic of conscious vision. Other visual phenomena and functions, like interference or inference, are less strongly linked. Feature detection and higher-level categorization clearly do not mark the transition from unconscious to conscious vision. From a neural perspective, it can be argued that conscious processing is linked to those operations that require spatially and temporally extended processing, where neurons engage in incremental interactions involving many steps. These processes are selectively dependent on horizontal and feedback connections. Moreover, these interactions induce learning, as they operate along highly plastic neural pathways, and use the molecular machinery that is directly involved in neural plasticity.
We can now start using these defining characteristics to answer more difficult questions. Is there consciousness in the right half-brain of a split brain patient (Sperry 1984)? Is there consciousness without attention (Koch & Tsuchiya 2012)? Is there consciousness in neglect or extinction (Lamme 2003)? Is it appropriate to talk about inattentional “blindness”, where people do not remember having seen something while their attention was engaged elsewhere? What exactly happens during change blindness (Simons & Rensink 2005)? Is there consciousness in animals (Edelman & Seth 2009), or in a vegetative state (Owen et al. 2006)? These are the “dolphins” of consciousness research, situations that are hard to position in the current taxonomy of conscious versus unconscious, because much controversy exists about the presence or absence of conscious experience in those conditions. With this, I hope to have given some usable arguments that can settle such controversies. My claim would simply be that whenever we see the defining properties of conscious vision that have been laid out here (i.e., incremental Gestalt grouping and segregation), there is conscious vision, regardless of whether there is conscious access or report (e.g., Scholte et al. 2006). More in general, the more fruitful stance towards consciousness would be to let all the available evidence converge into general theses, such as those derived here, and then take these as the defining characteristics of conscious processing and consciousness, regardless of whether they fit our introspective intuition of what consciousness is or should be. Defining consciousness as the process that builds on spatio-temporally extended neural processing (STERP property), that enables the building of super-positioned representations that individual modules cannot provide (SUPER property), and that evokes synaptic plasticity and learning (LEARN property) yields clear defining characteristics. These characteristics go a great length towards elucidating important features of phenomenality (its integrated nature, Gestalt properties), towards explaining the nature of conscious experience (perceptual organization, interference, inference), and are hinting towards a potential function of consciousness (learning) and its molecular basis. What I consider irrelevant characteristics (such the ability to report about an experience, see Lamme 2010a, 2010b) generally do no such explaining. It is better to build a taxonomy of conscious versus unconscious processing on defining characteristics than on irrelevant ones. That has helped a lot in positioning dolphins in the taxonomy of species. It will also help a lot in positioning the wild amalgam of phenomena that the field of consciousness research has produced so far. And it will enable us to give consciousness its proper ontological status. But I have already contributed to that discussion extensively elsewhere (Lamme 2003, 2004, 2006, 2010a, 2010b), so I will lay that to rest here.
At the crack of dawn, something magical happens. Night turns into day, life springs, vibrations fill the air. We know, it is just the earth rotating. But a very fundamental transition it remains. Unconscious or conscious processing, it’s all neurons doing their job, firing action potentials, exchanging chemicals, transferring information. But somehow, suddenly, they “turn on the light”. You see. You have a conscious sensation of that dawn. Isn’t it beautiful? You should take a picture of it.
Acknowledgements
This work was supported by an ERC Advanced Investigator Grant (DEFCON1, nr 230355 ) to Victor Lamme.