Distinctions of Consciousness
2.0 Distinctions of Consciousness
Ned Blocks distinction of consciousness into two types called phenomenal consciousness (P-consciousness) and access consciousness (A-consciousness) 1 conveniently organizes and categorizes our brain processes. The physically classification of this is the evolutionary ancient pathways such as the brain stem and amygdala corresponds to p-consciousness while the recently evolved pathways consisting of the pre-frontal cortex corresponds to a-consciousness. Even though consciousness as we perceive as irreducible we are aided in explaining the unity of consciousness by using Blocks’ distinctions. Classifying cognition into two different brain structure architectures allows the artificial general intelligence problem to be re-framed. The prospective theory for modeling human level intelligence must explain how unconscious and conscious processes create our tool making and behavioral variety. The below excerpt further explains the distinctions.
P-consciousness, according to Block, is simply raw experience: it is moving, colored forms, sounds, sensations, emotions and feelings with our bodies and responses at the center. These experiences, considered independently of any impact on behavior, are called qualia. A-consciousness, on the other hand, is the phenomenon whereby information in our minds is accessible for verbal report, reasoning, and the control of behavior. So, when we perceive, information about what we perceive is access conscious; when we introspect, information about our thoughts is access conscious; when we remember, information about the past is access conscious, and so on. David Chalmers has argued that A-consciousness can in principle be understood in mechanistic terms, but that understanding P-consciousness is much more challenging: he calls this the hard problem of consciousness.
Blind sight patients provide a superb example of this perceived duality of consciousness. When the V1 or striate cortex of a person is damaged then the individual will have an area of blindness known as a sotoma. But since this route from the retina to the visual cortex is not the only pathway from the eye, these patients can still unconsciously realize that something is in their visual field to the extent that they can guess its motion without being aware of it. This ability remains because of the preserved pathways into the extrastriate cortex that bypass V1. The preserved pathways provide judgments for decision making allowing blind sight patients to even have the ability to navigate mazes 2. In this case the patient suffered two strokes and was profoundly blind yet the astonishing result was that the patient also had a response to the facial expressions of others. In other cases, blind sight patients were presented with fearful images; the patients then would exhibit a cringe at a faster response time then patients with no blindness whom are able to use their visual cortex 3 4.The results show that even though they are unaware of stimuli because of their damaged pathways, they can still react and make judgments using alternative instinctual pathways. In these cases the patient is unaware of images but the alternative un-conscious pathways output the phenomenal experience of a primal and instinctual response. The un-conscious pathways have a natural, instinctual, and unavoidable sensation because the individual is not aware of the steps or brain computations that leads to the information they feel. Access consciousness will then compute a decision using the phenomenal information in conjunction with logic and learned knowledge.
Since phenomenal consciousness is instinctual in nature, it’s very difficult to overcome the intrinsic attractiveness or aversion for positive or negative quale. The a-conscious workload is far more difficult if it tries to change the valence of a fearful quale into a positive one. Examples of this would be overcoming a fear of snakes or squeamishness at the sight of blood as well as irrational fears we all possess.
A further elaboration of this can be made with the philosophical thought experiment of Mary the scientist who was born color blind who on her 40th birthday she had a procedure done to restore her vision. Beforehand, she only knew the physical facts about the color red, but now she can compute a valence for every instance of red she experiences. Prior to the procedure the visual attributes of red could only be verbally explained to her and another person would have to tell her whether a color is red or green. Her new found capability allows her to judge a red quale and identify it as a unique experience. Now that red phenomenal information can be inputted into her brain she can use the valence of the quale for behavioral decision making.
For certain color blind individual’s red is experienced the same as green 5 6. Without the ability for distinctions between the shades of those colors there is no separate quale experienced. This results in a inability to distinguish between shades of red and green. Physiologically this occurs because the brain or eyes are physically incapable of receiving green wavelengths. The physical realization of green symbols cannot be grounded for these individuals. The lack of perception creates an information loss where the individual is unable to have an emotion for green.
In another example of the explanatory argument, Broad argues that by knowing the complete structure of ammonia molecules and even predicting the changes in the olfactory nerves would not give someone the ability to deduce the smell of ammonia 7. This is because again the information of “what it is like” to smell ammonia is computed by the brain from the experience of being near ammonia. When the smell is phenomenally experienced then the brain computes a valence that is based on one’s survival needs and desired preference. The unconscious or phenomenal-consciousness pathways compute the valence based on survival needs, while the access-consciousness pathways contribute by supplying the desired preference for smells as well as creating an empirical description.
The valence of the experience is a product of the dynamic physical processes undergone in the brain and the quale in attention. We possess free will in the sense we possess intentionality, but we do not have control of how experiences feel. Amazingly though every one of us still has a unique subjectivity of experience.
1 Block, N. (2004). The Encyclopedia of Cognitive Science.
Block, N. (1995). ON A CONFUSION ABOUT A FUNCTION OF CONSCIOUSNESS. Behavioral and Brain Sciences 18 (2): 227-287.
1 Block, Ned. “Two neural correlates of consciousness.” Trends in cognitive sciences 9.2 (2005): 46-52.
Block, Ned. “How many concepts of consciousness?.” Behavioral and brain sciences 18.02 (1995): 272-287.
2 Briggs, Helen. “Blind man navigates maze.” BBC News. N.p., 22 Dec 2008. Web. 02 July 2012. <http://news.bbc.co.uk/1/hi/health/7794783.stm>.
3 Tamietto, Marco, and Beatrice de Gelder. “Affective blindsight in the intact brain: Neural interhemispheric summation for unseen fearful expressions.”Neuropsychologia 46.3 (2008): 820-828.
4 Ptito, Alain, and Sandra E. Leh. “Neural substrates of blindsight after hemispherectomy.” The Neuroscientist 13.5 (2007): 506-518.
5 Sharpe, Lindsay T., et al. “Opsin genes, cone photopigments, color vision, and color blindness.” Color vision: From genes to perception (1999): 3-51.
6 Morgan, M. J., A. Adam, and J. D. Mollon. “Dichromats detect colour-camouflaged objects that are not detected by trichromats.” Proceedings of the Royal Society of London. Series B: Biological Sciences 248.1323 (1992): 291-295.
7 Broad, Charlie Dunbar. The mind and its place in nature. Ed. Trench Kegan Paul. London: Routledge & Kegan Paul, 1925.
Chalmers, David J. “Consciousness and its place in nature.” Blackwell guide to the philosophy of mind (2003): 102-142.