The Varying Levels of Consciousness
Depending on the way you interpret consciousness, the levels at which it can exist also vary. To be able to define certain states or species as being 'unconscious' is to imply that there is a scale on which consciousness falls. Here we will explore the varying levels of consciousness as understood both within the neuroscientific interpretation and without.
Levels As Defined in Neuroscience
In the previous section, we determined that Neuroscience defines consciousness as the state or quality of being aware of external objects as well as oneself. This awareness is dependent upon two factors of the individual. First, The individual must be at a level of brain development where they can achieve said awareness in the first place, and second they must be in a transient state of awareness at the time they are being tested in order to be considered conscious. As an example, a mature adult human has the mental capacity to be consciously aware of their surroundings, however if they are in a transient state of sleep, they still qualify as unconscious. This duality within the neuroscientific definition is well represented in the distinction between phenomenal and access consciousness that is often cited within neuroscience.
Phenomenal consciousness in this case refers to an individuals subjective experience and their ability to interact and perceive the world around them. Phenomenal consciousness can be thought of as the transient scale of consciousness that varies for an individual on a short term basis. One's ability to experience the world around them is dependent upon their state, therefore consciousness can be considered a variable concept within this interpretation. One way to measure an individuals ability to receive and react to environmental stimuli is through the use of the Glasgow Coma Scale(GCS). When using the GCS, neuroscientists assess a patients arousal and responsiveness to certain tasks in various states. These assessments are then compared to a set of standards for various states of consciousness, called the Glasgow Coma Scale(GCS). The GCS measure 3 different aspects of awareness on up to 6 levels. These aspects are Eye opening, Verbal Response, and Motor Response. Level 1 of each aspect indicates no response, whereas the highest level is indicative of normal, functioning 'awake' levels of awareness and activity.
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Access Consciousness within neuroscience refers to the ability of an individuals experience to be transferred into other cognitive processes such as speech and memory. It is the connection between the ability to perceive the world around you, and the ability to interpret, remember, and share that world. Unlike phenomenal consciousness, access consciousness develops early in life (both pre and post-natally) and does not vary much on a large timescale.
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Glasgow Coma Scale
Phenomenal Consciousness:
Related solely to an individuals subjective experience. Phenomenal consciousness is an individuals first person experience, the levels of which are dictated by an individuals ability to perceive and interact with the world around them. For scientific purposes, it is the extent to which an individual can receive stimulation from the world independent of later cognitive processes.
Phenomenal Consciousness
Access Consciousness:
Access Consciousness refers to the ability of an Individual's experience to be transferred to other cognitive processes such as memory and speech. It is the connection between experience and verbal report/association of said experience. This form of consciousness develops throughout early childhood.
Access Consciousness
4. Open eyes voluntarily and spontaneously
3. Open eyes in response to direct speech
2. Open eyes in response to pain
1. No response
Eye Opening Response
5. Correctly oriented to time/person/place
4. Confused
3. Incorrect word usage
2. Incomprehensible sounds
1. No response
Verbal Response
6. Voluntary movement, obeys command
5. Moves with localized pain
4. Withdraw from pain
3. Abnormal Flexion
2. Abnormal Extension
1. No response
Motor Response
Prenatal Development:
~20 weeks: sensory receptors present in fetus
~22-26 weeks: thalamus and thalamo-cortical connections develop (thought to be necessary for sensory function)
~30 weeks: sleep-wake cycles distinctions detected
Postnatal Development:
~6 months: children can speak simple, few syllable words
~18 months-2 years: children can begin to form
2-4 word sentences, are able to express most experiences and thoughts verbally
Developmental Stages
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Levels of Consciousness Outside of Neuroscience
Freudian Levels of Consciousness
Conscious Level:
Thoughts, perceptions, and actions
Conscious
Preconscious Level:
Memories and Stored Knowledge
Preconscious
Unconscious Level:
Fears, Instinctual Urges, Selfish Needs, Shameful Experiences
Unconscious
Psychoanalyst Sigmund Freud had his own interpretation of consciousness in which it is comprised of three different levels that are continually present within an individual. These levels represented stages of awareness of different factors of human experience. They are comprised of what he calls the conscious, the preconscious, and the unconscious.
The conscious represents all things we are aware of at a certain moment. This includes our thoughts, perceptions, and actions. Below the conscious level is the preconscious, which represents things that we could pay attention to if we desired but that we are not currently aware of. The preconscious is our memory and stored knowledge, the stuff we can dredge up if need be but do not automatically have in our attentional spotlight. Lastly, the lowest level is the unconscious, or what can also be thought of as the large bottom to the freudian consciousness iceberg. The unconscious represents what is completely outside of our conscious knowledge. The unconscious according to freud is what drives a large part of our actions as it is comprised of our fears, animalistic urges, and other unpleasantries.
The 'Scala Naturae'
Otherwise known as the 'Scale of Nature,' the Scala Naturae was originally derived from a taxonomic ordering of all things, from minerals to god, ranked by perfection and devised for religious reasons. St. Albertus Magnus, in defense of this linear method for organization of all beings once stated "Nature does not make [animal] kinds separate without making something intermediate between them; for nature does not pass from extreme to extreme without an intermediate." This formed the basis of the 'Law of Continuity,' an idea that Charles Darwin supported as well.
Though the scale in it's entirety is no longer used as an accurate method of classification for many species, it's linear organization still influences present classification classification methods used by biologists. Additionally, this hierarchical ordering may still be used for certain concepts, consciousness being one of them. One way to view the levels of consciousness is on the scale of species to species relationships, placing species with lower cognitive functions on the side of possessing simple consciousness while higher order species such as humans with vast cognitive functions represent the opposite side of the scale as possessing complex consciousness. The species between the two extremes would then form a gradient of consciousness, each with a slightly different level of consciousness than their neighbors, as represented by the graphic below.
Fish
Amphibians
Reptiles
Birds
Simple Consciousness
Mammals
Humans
Complex Consciousness
So what can we learn from all of this?
The large range of interpretations of consciousness results in a correspondingly large range of ways in which consciousness is believed to vary. This variance takes place on several different scales. First, it varies on the scale of the day to day basis of an individual as well as over the individuals lifetime as seen in the neuroscientific interpretation. Next, according to the Freudian definition, it varies according to levels accessibility at a given time. And lastly, according to the Scala Naturae, it varies spectrally between species. This contributes to the complexity of consciousness in that not only is there no singular unified definition, but also each of the existing definitions uses very different quantifications to categorize levels of consciousness. However, non of these categorization levels are entirely mutually exclusive. They can exist co-dependently and can serve to label varying consciousness from different points of view. But, in reference to the Scala Naturae, is consciousness truly a gradient scale between all species? And can a point in evolutionary history be found where consciousness begins?