Blindsight: The Reality That Isn't "There"

Abstract:

Previously consciousness has been a concept to which only philosophers, and later psychologists, have aspired to describing. However, it is now believed that neuroscience may offer a means for reaching a better understanding of consciousness, including locating a neurological correlate of consciousness (5). The phenomenon known as “blindsight” has given rise to several rounds of research that have produced multiple theories pertaining to visual consciousness, the consequences of which force one to question previous notions of awareness, experience and the mind-body relationship. This paper begins to examine some of the major theories that have emerged from studies of blindsight and discuss their implications on our previous notions of consciousness, including as it relates to Aristotle’s notion of the soul. Within this subject, there are yet to be any truths to conclude. Consequently the goal of this paper is not to innumerate truth, but instead to provoke thought about everyday experiences of consciousness.

Foreword:

The vary nature of this topic (consciousness) lends itself to confusion and ambiguity. Consequently, a brief discussion of the language used in this paper is necessary. Terms such as awareness and consciousness are applied in a sense that does always not refer to consciousness as one would typically take it to mean. Let it then suffice that terms such as “consciousness” and “awareness” [within quotations] refer to a lack of introverted awareness or a lack of “I-function” involvement, whereas awareness and consciousness [no quotations] refer to “I-function” accessibility, the idea of consciousness with which one typically associates. Consciousness [italicized] will refer to the general subject in its totality, limited to neither one of these notions. I apologize for any subsequent confusion arising from these distinctions.

Further, within this line of questioning, the research is plagued with the clear difficulty of subjectivity; one cannot know what is occurring within the conscious mind of another. Hence this research relies heavily on first, believing the subjects, and second, the subjects ability to discern their own consciousness. Even in approaching an understanding of consciousness through neurological and psychological processes, one should not limit oneself to considering facts only provable by objective, empirical studies.

Discussion:

An aspect of Aristotle’s examination of consciousness can be found in the treatise De Anima. Here Aristotle examines the nature of living things said to possess a soul, also referred to as a psyche. Aristotle postulates that different being possess different forms of psyche, with a primary distinction between a nutritive [basic] psyche, which is capable of living and reproducing, and a perceptive psyche, which has the capacity to sense. Plants, for example, possess a nutritive psyche, while higher life forms are capable of perceiving their surroundings. While plants may be said to respond to their surroundings, the beanstalk growing towards the light, it is safe to say that plants do not do so by choice. Or rather, plants do not perceive their surroundings with any awareness. As Aristotle describes, the capacity to sense necessitates a level of awareness [“consciousness”] (1). Currently, the predominant understanding of perception concurs with the notion laid out by Aristotle. However, should one necessarily believe that the perception of objects necessitates an awareness of doing so? If so, what is the nature of this awareness? How does one become aware of one’s perceptions? The rare condition of “blindsightedness” points to the possibility of perception without awareness, without the “I-function” of consciousness. What implications does blindsightedness have for the concepts of perception and consciousness?

What is sensing or perceiving? Aristotle proposes that a perception [e.g. sound, image] requires an acting body, a passive body to be acted upon, and a space between the two (1). Using sight as an example, one cannot actually see color, or the colored, if there is no light being reflected off an object, across a space, to one’s sense organ [the retina of the eye]. Instead, one can only potentially see the color of the colored. A wall painted red, in the absence of light, is only potentially red. Likewise, a man standing before this wall, in the absence of light, can only potentially see the wall. The potential image of the wall is actualized in the presence of light, with the concurrent actualization of the wall’s redness and the observer’s sight.

What occurs within this movement? How does the image of the wall impress upon the viewer’s mind? Here it should also be understood that there could be no image of the wall if there were no one there to see the wall, as a tree falling in the woods produces no sound if no one is there to hear it. So perhaps one should not say the image is impressed upon the viewer’s mind, but rather that it is realized in the viewer’s mind. This realization implies an internal awareness of the perception. Aristotle explains that sensing is not merely affection by a sensible object, as would be the case if the image were merely imposed on the viewer. For example, light waves may reflect off clouds and reach the leaves of a plant. While a chemical effect will be produced in the chlorophyll of the plant, one would not say that the plant “saw” the clouds. Contrarily, a man can “see” the clouds because he becomes aware of an image of clouds in his mind. The distinction between affection and perceiving then is the presence of a consciousness, or an awareness of having been affected by the clouds. Is Aristotle correct in making this distinction? If so, does this mean one can only be said to see if one is aware that one is seeing?

Concurring with Aristotle’s proposal, it is currently understood that visual perception requires the simultaneous actualization of the object’s potentiality to been seen and the subject’s potentiality to see [with the presence of light]. In other words, visual perception requires that the object of perception lie within the subject’s field of view and reflect sufficient amounts of light to the subject’s retinas to induce a pattern of activity in the photoreceptors (3). In addition to this prerequisite, seeing, or more specifically, visual perception, requires three primary conditions (2). First, the contrafactual condition, which refers to the necessity of an object’s presence in the field of view of a subject in such a way that it offers a visual perception unique to that object. In other words, the visual perception would not have occurred as it did without the object. Second is the condition of consciousness, which requires that the subject consciously experience the phenomenal qualities of the perception. Phenomenal qualities, also called qualia, refer to the qualitative differences between experiences that distinguish them from one another (3). For example, when one hears lightning, the qualia of hearing make it apparent to the subject that he is hearing [and not seeing, smelling etc.]. As the second condition implies, in order for the subject to realize that he is hearing, he must consciously experience the qualia of the perception. The third condition is the epistemic condition. This states that if a subject sees an object, then the subject inherently predicates beliefs about that object. The phenomenon of blindsight diverges from the realm of normal vision due to an apparent deficiency of consciousness, violating the second condition of visual perception. However, in order to understand this alleged lack of consciousness one must first examine the characteristics of blindsight.

Lawrence Weiskrantz and colleagues first discovered blindsight while studying a patient, DB, who had become blind in his left field of view following surgical removal of his right occipital lobe. Weiskrantz found that DB was able to point with relative accuracy towards an object occupying the blind area of DB’s visual field, and further, that DB was able to guess as to the shape and orientation of these objects with greater accuracy than chance alone would permit. During these tests, DB sincerely maintained that he could not see these objects (4). Weiskrantz classifies blindsight as a behavioral pattern exhibited under particular conditions by subjects who have sustained damage to their striate cortex, creating holes in their field of view (3). These conditions stipulate first, that the perceiver claims to be incapable of seeing an object that lies within one’s normal field of view that reflects a sufficient amount of light to the perceiver’s eyes to be seen under normal circumstances. Second, the perceiver demonstrates behavior indicative of stimulation by the object he claims not to see. Finally, the perceiver must be capable of seeing the object when it is projected to his field of view that has not been affected by cortical damage.

The fact that the blindsighted subject sincerely claims not to see the object stimulus, despite being able to point towards it, suggests that the subject has no immediate awareness of the visual experience; the perceiver is unaware of both the light his eyes have absorbed and his brain’s processing of this light (3). In other words, the perceiver is not conscious of the visual perception, but this does not mean that the perceiver has failed to experience visual perception. Here there seems to arise contradiction, as conscious awareness seems to be a necessary facet of experience. How can one experience nonconsciously? There is a distinction between conscious awareness and nonconscious “awareness”. Conscious awareness is the condition whereby a subject has an internal apprehension of being aware of an object of visual perception [an awareness of the awareness]. While nonconscious “awareness” refers to the condition of a subject who is only “aware” of the object (3). To then experience nonconsciously means that an object of perception has left an effect on one’s nervous system without making him aware of that effect. It can now be seen how blindsight diverges from normal sight: While in normal sight one is aware of the visual experience, in blindsight one only has “awareness” of the object of visual experience.

Since blindsight implies that a subject does not consciously experience the qualia of visual perception, it follows that his intentionalities [e.g. pointing to the object] occur without phenomenality, as proposed by Norton Nelkin. Intentionality refers to an inner “apprehension” of the visual experience, of which the perceiver’s I-function has no awareness. These internal “apprehensions” are the aforementioned effects left by the object of sight. How a subject acts when asked to point towards an object occupying the subject’s blind area will be directly affected by this internal information, but without the subject being made aware of it (3). Weiskrantz, too, suggests this notion of disconnect of awareness and performance within blindsight. If performance is occurring without awareness, what does this say about the relation between mind and body? It is being suggested that the subject points to the object without knowing why he has done so, or without knowing he has done so. If this is the case, ultimately the subject’s actions would not be under conscious control. How much control does one’s I-function really have over one’s actions?

The subject pointing towards the object that he does not see is being affected by an object, which for him, does not exist. Yet this object does exist, and it is directly influencing his behavior. Reality, then, cannot be limited to that which one perceives. Rather, reality should also be qualified as that which one “perceives.” This returns to Aristotle’s notion of a nutritive psyche versus a perceptive psyche. The nutritive psyche would constitute that which is “aware” of the world while the perceptive psyche is aware of the world. Aristotle would then say that to be “aware” of the world is not to sense the world; the man with blindsight is not seeing if he is not aware that he is seeing. Instead, the man is merely being affected by light as a plant is affected by light. A plant will grow towards the light just as the man can point towards it. Is Aristotle right? Should one define seeing as an awareness of the visual experience? Or could one say that seeing only requires the visual experience itself accompanied by the “awareness” it produces?

Does this research implicate the cortex as the structure ultimately responsible for separating humanity from other organisms? Damage to the cortex damages the perceptive psyche, forcing a subject to fall back onto the basic, nutritive psyche, one that does not have self-awareness. This seems to suggest that the cortex is what permits humans to possess a soul, a higher perceptive psyche. Additionally, might this suggest that qualia do in fact exist if it is qualia perceived that allows one to perceive in the first place? Does the cortex have specialized receptors for this qualia? Blindsighted patients may have an “awareness” of the object of visual experience, but they are not aware of the phenomenal qualities. Lacking this phenomenality, a subject with blindsight could not know that he is seeing. Hence the subject wholeheartedly claims not to see an objected presented to the area of his field of view corresponding to his cortical damage. Would this mean that the striate cortex is responsible for processing visual qualia, thus creating visual consciousness? The asnwer: a definite maybe yes, maybe no. The truth is, there is really too much activity involved with visual perception to pinpoint when and where visual awareness arises. In the end, we are only left with more questions.

Sources

1) McKeon, Richard, ed. The Basic Works of Aristotle. New York: Random House, 1941.

2) Blindsight and the Role of the Phenomenal Qualities of Visual Perceptions, Freely accessible paper by Ralph Schumacher regarding visual perception

3) Blindsight and Consciousness, Thomas Natsoulas. The American Journal of Psychology, Vol. 110, No. 1. (Spring, 1997), pp. 1-33. Accessed through JSTOR via Haverford.

4) The consciousness of sight, Freely accessible paper by Adam Zeman provided on pubmed

5) Towards A True Neural Stance on Consciousness, Victor A.F. Lamme, Towards a true neural stance on consciousness, Trends in Cognitive Sciences, Volume 10, Issue 11, November 2006, Pages 494-501. Accessed through ScienceDirect via Haverford.