Different qualia are qualia that have different phenomenal characteristics even if they are qualia of the same thing. For example, qualia of a color “C” may have phenomenal characteristics as red in some people, but as blue, green, or other colors in other people. Theoretically, there are many possible types of different qualia. They can be classified into three major types as follows.
9.1. Objectively different qualia
9.2. Randomly different qualia
- 9.2.1. Completely randomly different qualia
- 9.2.2. Partially randomly different qualia
9.3. Restrictedly different qualia
- 9.3.1. Inverted qualia
- 9.3.2. Shifted qualia
- 9.3.3. Parallel qualia
Figure 9.1 Different Color Qualia among People
It has long been suspected that, in perceiving things in the outside world, people may have different qualia of the same thing occurring in their minds. As noted above, some people think that when people look at the same color C, the color quale of red may appear in some, while the color quale of blue, green, or other colors may appear in others [1-5][Figure 9.1]. It is also possible that some extraordinary colors that are not in the color spectrum that general people perceive may occur in some people’s mind. Yet, they will all call what they see the same, “color C”, even if the phenomenal characteristics of the color in their minds are different. Even more bizarre possibilities are that other types of qualia, such as auditory qualia, olfactory qualia, or qualia of unusual percepts that do not occur in general people, may occur instead of the color quale in some people! And all of them will still call it “color C”! Notably, at least at present, there is no way to verify whether all these qualia in different people actually have the same or different phenomenal characteristics and, if they are different, which one of them is the correct quale of the color C. However, is this scenario possible – can qualia of the same thing in different people be such randomly different?
The answer, according to Theorem VI1 and Theorem VI2: Identical/similar neural processes have identical/similar mental processes and identical/similar qualia, is “no”. But is there evidence that they really cannot be randomly different and that both theorems are true?
9.1. Objectively different qualia
First, it must be noted that different qualia of the same thing among people are possible objectively because many physical, anatomical, and physiological factors are involved in the process of perceiving anything and because these factors – which have effects on perception neural processes and their signaling patterns, which will inevitably affect perception mental processes and qualia – are different among people. For example, in a case of perceiving a color, the involved physical factors in the outside world (such as the light that shines on the color, the light’s angle of incidence and of reflection, and the intervening medium between the color and the observer’s eyes) and the anatomy and the physiology of the whole visual perception pathway (from the cornea of the eyes to the neural circuits for visual perception) are slightly different in different people. So, the resulting perception neural processes and their signaling patterns, together with their mental processes and qualia, will be slightly different, and it is very likely that people will consciously experience (mentally see) the same color differently, but only subtly if their brains are normal and if other factors are very similar. This kind of different qualia that result from objective differences in physical, anatomical, and physiologic factors is called objectively different qualia in this theory. The differences among objectively different qualia of the same thing in different people are usually subtle because the differences of the resulting neural processes and signaling patterns among people are only slight, as noted. Drastic differences among objectively different qualia of the same thing under similar perceiving conditions in normal people are not possible and do not occur.
Synesthesia is a condition in which a stimulus in one sensory modality automatically and consistently triggers concurrent percepts in another modality [6-23], or in another form of the same modality. For example, people with color-music synesthesia will have color perception occurring when they hear musical sounds [17,21] and people with grapheme-color synesthesia will have the perception of colors occurring when viewing letters or numbers [8,9,10,14,15,18,23]. Many scientists believe that synesthesia occurs because there are unusual neural connections between perception neural circuits of different modalities such that, when a perception neural circuit of one modality (such as auditory) is stimulated to function by some stimulus, another perception neural circuit of different modality (such as visual) will function simultaneously (such as in people with color-music synesthesia). In other types of synesthesia, the unusual neural mechanisms activate perception neural circuits of different types but of the same modality, such as between visual perception of form and visual perception of color in people with grapheme-color synesthesia . Other possible underlying mechanisms for synesthesia generations are disinhibited feedback, hyperconnectivity/hyperbinding, or enhanced white matter connectivity . However, the evidence from some studies have shown that synesthetic experience (e.g., synthetic perception of colors) is not equivalent to true perception (e.g., perception that occurs in seeing colors)  and that the cause of synesthesia may be something else, such as a special kind of childhood memory that is recalled when there is some sensory perception  or distributed processing of synesthetic associations . However, despite the uncertainty of what the exact mechanisms that generate synesthesia are, it can be concluded in general that they are physical mechanisms involving neural connections and/or functions.
Qualia that occur in people with synesthesia are thus different from qualia in general people experiencing the same thing because there are more than one type of qualia occurring simultaneously. And because these different qualia occur due to some physical mechanisms, they are objectively different qualia, too.
Objectively different qualia are not evidence that Theorem VI1 (Identical neural processes have identical mental processes and identical similar Qualia) is wrong because the conditions that create objectively different qualia are not identical. Theorem VI1 is valid only in identical conditions.
9.2. Randomly different qualia
Excluding objectively different qualia, is it possible that identical subjects perceiving the same thing in the outside world under the same condition have different qualia occurring in their minds? And, if we examine this question down to the level of neural processes, is it possible that identical neural processes (in the same person or different persons) perceiving the same thing in the outside world under the same condition have different qualia occurring in their processes? If the answer is “yes”, it means that qualia of the same thing can be different in different subjects and different neural processes not because of objective physical factors but because of the nature of the qualia to be arbitrarily or randomly different in different subjects and different neural processes. This type of different qualia may be called “subjectively different qualia” in contrast to “objectively different qualia” because they are not determined by objective factors. However, as there are no subjective factors that determine how qualia will be in each subject or neural process, the term “subjectively different qualia” may not be appropriate. Because the principal feature of this kind of different qualia is that they can be randomly different in different subjects and different neural processes without any rules, they should be more aptly called randomly different qualia (RDQ), and this is the term that will be used in this theory. RDQ can be classified into 2 groups, depending on whether they are completely random or are partially random.
9.2.1. Completely randomly different qualia (CRDQ) are qualia that appear randomly different in all neural processes, no matter whether they are identical or not and no matter whether they are in one individual or in different individuals. They are thus complete in their randomness.
9.2.2. Partially randomly different qualia (PRDQ) are qualia that do not appear randomly different in identical neural processes that are in one individual but appear randomly different in identical neural processes that are in different individuals. They are thus only partial in their randomness.
Now, the question is whether RDQ do occur in the real world. To answer this question, we shall examine the two types of RDQ one by one as follows.
9.2.1. Completely randomly different qualia (CRDQ)
For CRDQ – qualia that appear randomly different in all neural processes, no matter whether they are identical or not and no matter whether they are in one individual or in different individuals – there is evidence that they do not occur in the real world. Consider this example:
A visual image that occurs in one’s mind is not an all-or-none phenomenon, i.e., it is not that the image must occur as the whole image or not occur at all. Instead, the whole visual image is composed of millions of independent tiny visual images, which contain visual information of their corresponding points in the visual field, joined seamlessly together by the visual perception neural processes. Each tiny visual image is the result of a tiny perception neural process of that point in the visual field. If there is damage to some of these tiny neural processes, the damage will affect only them and will be reflected in the corresponding points of the visual field, leaving the non-affected part intact. For example, a lesion of a portion of an occipital cortex can result in a scotoma (defect) in the corresponding portion of the visual field, leaving the rest of the visual field undisturbed. Also, as there are separate perception neural processes for each specific characteristic (color, shape, movement, etc.) , various types of defects can occur separately and independently of each other. For example, a unilateral occipito-temporal infarction can result in a contralateral hemi- or quandrantic achromatopsia (cerebral color blindness in a half or a quarter of visual field) [27-30] while other components (shape, dimension, movement, etc.) of the vision are still intact. Thus, the whole visual image in the mind is composed of millions of independent tiny visual images, each composed of several independent types of visual characteristics.
Now, suppose one is looking at a screen of homogeneous color “C” (Figure 9.2).
All the tiny neural processes for color perception must be creating the same signals – the color “C” signal – separately; and the quale for each tiny neural process must be occurring separately. If CRDQ are possible, each quale of the millions tiny neural processes that generate the whole image should manifest itself differently as red, blue, green, or other colors randomly, and the whole visual image should not be a homogeneous color but a mixture of myriad different color bits (as in Figure 9.3). But in reality, this does not happen. A screen of pure red color (Figure 9.4) is always perceived as a pure red screen (as in Figure 9.4), not a screen of numerous different colors (as in Figure 9.5).
Similarly, a pair of same-color discs (red and red, Figure 9.6) are always perceived as a pair of same-color discs (red and red, as in Figure 9.6), not a pair of different-color discs (such as red and blue, as in Figure 9.7), which can occur if CRDQ are possible.
Even a pair of same-color discs that are separated in different visual fields (Figure 9.8) are always perceived as a pair of same-color discs (such as red and red, Figure 9.8), not a pair of different-color discs (such as red and blue, Figure 9.9), which can occur if CRDQ are possible.
So, it means that, for the same color in the outside world, the same color qualia occur in all those millions tiny neural processes and that CRDQ do not occur. Also, it never happens that color qualia occur at some points in the visual field but auditory, olfactory, or other kinds of qualia occur at other points in the visual field. This means that the signals from all the tiny neural processes for color perception are generating only visual qualia, not randomly different kinds of qualia.
Similarly, with the same consideration, there is no evidence that CRDQ ever occur in other sensory perceptions either. For example, when someone hears two identical musical instruments playing the same musical note “M” (M stands for a certain musical note), the quale of each sound has the chance to manifest itself differently if CRDQ are possible: one may appear as the piano sound of note C and the other as the violin sound of note G. This is, of course, absurd and never happens – he/she always hears the two sounds as the same musical note of the same musical instrument, such as the flute sound of note A if it is the flutes playing the note A. The same scenario is similar for other sensory perceptions, such as the feeling of the same touches on both arms, the pain from the needle stabbing with similar strength on both legs, and the taste of sugar on both sides of the tongue – the qualia of the same things on both sides are always the same, not randomly different.
Thus, evidently, there is no randomness in the manifestation of qualia. This “no randomness in manifestation” of qualia has been consistently true for a long time in billions of humans nowadays and in the past – no normal person has ever reported having a mixture of different qualia occurring when perceiving a homogenous stimulus or identical stimuli. Thus, even though CRDQ have had virtually infinite chances to manifest themselves, they have never ever done so. It can, therefore, be concluded that completely randomly different qualia (CRDQ) do not occur.
9.2.2. Partially randomly different qualia (PRDQ)
However, is it possible that randomly different qualia do not occur in an individual because all the tiny qualia occur in one single person, with one consciousness to experience the qualia, but that they will occur (manifest themselves differently) among different persons, with different consciousness to experience the qualia? If so, it means that, even though all the tiny neural processes in an individual are not the same one and are at different anatomical positions and even though the neural processes on the right and on the left hemisphere are widely separated, these dissimilarities are not enough for qualia to manifest themselves differently and that it requires different individuals for qualia to do so. If this is the case, then such qualia are not “completely randomly different qualia” but are “partially randomly different qualia” (PRDQ) because they do not appear completely randomly different; only in some circumstances – in different individuals – will they appear so.
Now, is there evidence that PRDQ do occur or do not occur? The answer is that there is evidence that PRDQ do not occur either. Consider a pair of red disc and blue disc in Figure 9.10 below. Everyone with normal color vision will agree that the two colors are markedly contrasting in their hue. However, if PRDQ are possible, the red disc can appear as a yellow disc and the blue disc as a green disc in some people by chance, and the pair will be of yellow and green color discs as in Figure 9.11. In those people where the qualia appear as yellow and green will say that the two colors are not markedly contrasting in their hue, in disagreement with people who see them as red and blue. The disagreement will be even more obvious if the pair of red and blue discs is perceived as a pair of yellow and light yellow discs, which can occur in some people if PRDQ are possible. But such disagreement never occurs in billions of people with normal color vision. This is evidence that even PRDQ do not occur.
Other visual evidence is a color wheel. Everyone with normal color vision will agree that the hue of a color in the color wheel like the one in Figure 9.12 gradually changes from one disc to another successive disc. However, if PRDQ occur, the color quale of each disc in the wheel will manifest itself haphazardly and result in a color wheel that the hues of successive discs do not gradually change, like the color wheel in Figure 9.13, in some people. But this never happens in billions of people with normal color vision. They always agree that the hues of the colors in the color wheel like the one in Figure 9.12 gradually change from one successive disc to another. So, PRDQ do not occur in this case either.
The evidence in auditory perception is that if PRDQ occur, the sound qualia of musical notes must be randomly different among people. For example, some may perceive the sound quale of a certain musical note “M” as the note C, some as the note F, and some as the note A#, and for the next sound that is one semitone higher, or note “M#”, some people must randomly perceive it as note C#, some as the note Cb, and some as the note G, by chance. A musical scale must sound different among people if PRDQ occur. Also, a train of musical notes that have sound qualia as C-D-E-C-E-C-E in some people may have sound qualia as F-E-G-F-G-F-G in some people and as something else in others; a train of musical notes will appear as music for some people, but as an erratic train of sounds in others. But these strange phenomena never happen. People agree on the orderly sounds of a musical scale, the sound that is music, and the sound that is chaotic. This is similarly true for other sensory perceptions. For example, the sensory perception of a series of smoothly-increasing vibration stimuli or a series of smoothly-increasing sweetness stimuli will always be that the stimuli are smoothly increasing in strength, in all individuals. It will not be that in some individuals the perception is of haphazardly-changing-strength stimuli – which can occur in some individuals if PRDQ are possible.
Thus, evidently, there is no randomness in manifestation of qualia among different people. This “no randomness in manifestation” of qualia has been consistently true for a long time in billions of different individuals nowadays and in the past. Thus, even though PRDQ have had virtually infinite chances to manifest themselves, they have never ever done so. It can, therefore, be concluded that PRDQ do not occur among people in the real world.
9.3. Restrictedly different qualia
Still, is it possible that qualia can manifest themselves differently in people in some restricted forms that people perceive as identical? This kind of different qualia may be called restrictedly different qualia because they do not and cannot appear randomly different – there are some rules that restrict how they appear different in different people so that people cannot tell that they are experiencing different qualia. There are several possible kinds of restrictedly different qualia. Let’s examine some forms of restrictedly different qualia to see which kind can occur among people without people knowing that they are experiencing different qualia.
9.3.1. Inverted qualia
Inverted qualia are qualia that have a certain characteristic inverted. For visual qualia, there are a few kinds of inverted qualia. One of them is the inverted light spectrum qualia in Figure 9.14.
Figure 9.14 Inverted Light Spectrum with Respect to the Wavelength
Generally, when people with normal color vision see a spectrum of light like the one in panel A, they will agree that there are definite changes in color hue around wavelengths of 410, 470, 490, 570, 590, and 610 nm. If the qualia of light spectrum are inverted with respect to the wavelength in some people, the light spectrum will be like that in panel B. Evidently, people with inverted qualia would not agree with the previous observation – for them, definite changes in color hue occur around wavelengths of 510, 530, 550, 630, 650, and 710 nm. But people with normal color vision never disagree around what wavelengths a light spectrum changes color hues. So, there is no evidence that inverted color qualia of this kind really occur in people.
Another way to invert the color spectrum is to invert each color to its complementary color (color inversion). The will result in an inverted spectrum that looks like the one in Figure 9.15.
Figure 9.15 Inverted Color Spectrum by Color Inversion
The inverted spectra in this way still have problems of different changes of hue along the spectra. For example, from wavelength 580 to 640 nm, the upper spectrum (A) changes from yellow to red, the definitely different hues, but the lower spectrum (B) changes from dark blue to light blue, the slightly different hues. Also, between wavelength 510 and 590 nm, the upper spectrum (A) appears as green and yellow, the fairly close hues, but the lower spectrum appears as magenta and dark blue, the quite different hues. Therefore, if this kind of inverted spectrum really occurs among people, people will be able to tell that they are experiencing different color spectra. But this does not happen. So, there is no evidence that inverted color qualia of this kind really occur in people, either.
For auditory qualia, inverted chromatic scales, such as scale 1 and scale 2 below, will have different effects when chords are constructed. (The primed C, C’, is one octave higher than the unprimed C.)
Scale 1: C C# D D# E F F# G G# A A# B C’
The chord constructed from the 1st, 5th, and 8th notes (C-E-G) will sound like C Major.
Scale 2: C’ B A# A G# G F# F E D# D C# C
The chord constructed from the 1st, 5th, and 8th notes (C’-G#-F) will sound like F Minor.
So, the chords from both scales will be different. As major chords and minor chords have different musical effects, such as major chords are usually more vibrant and minor chords are more somber, people will not agree on what the mood of the chords is, which is usually not the case. And certainly, all professional musicians agree on what major and minor chords sound like. There must be some chords that they must disagree if inverted auditory qualia occur among them. There is no evidence that this has ever happened.
9.3.2. Shifted qualia
Figure 9.16 Shifted Light Spectrum along the Wavelength
Shifted qualia are qualia that the spectrum of their qualia is shifted. The situation in shifted qualia of a light spectrum is like that in inverted qualia. If the spectrum of light is shifted, such as shifted to the reader’s left side as in panel B (Figure 9.16), although we cannot say definitely about new color qualia that occur in the vacated portion, it is evident that people with shifted qualia will not agree with people with non-shifted qualia about at what wavelengths the light definitely changes color hues. But this kind of disagreement never happens. So, like inverted-spectrum qualia, there is no evidence that shifted light-spectrum qualia occur among people.
For shifted sound-pitch qualia, when the spectrum of sound-pitch qualia shifts up or down in different people, it is impossible to prove behaviorally whether they occur or not. This kind of different qualia can certainly happen objectively because of physical factors described above – some people may hear sounds in slightly higher or lower pitches than other people because of anatomic and/or physiologic factors in their auditory perception pathways. But, excluding objectively different qualia, behaviorally, there are no ways to tell that shifted sound-pitch qualia among people or not.
9.3.3. Parallel qualia
It is possible that there are other kinds of inverted or shifted qualia that may occur among people and that people perceive as similar (please see ref 31). However, one kind of different qualia that can theoretically occur in people without people being able to tell that they are experiencing different qualia is parallel qualia. Parallel qualia come in sets. Each set of parallel qualia is composed of qualia that have unique phenomenal characteristics that are different from their counterparts in other sets. But all the internal relationships among qualia in a certain set are similar to those in other sets. Thus, these sets of qualia can be considered parallel to each other with respect to their internal relationships. One example is the shifted sound qualia discussed in the previous section. All sets of shifted sound qualia have internal relationships among sound qualia in each set identical to internal relationships of sound qualia in other sets, such as the repeated similar sound every octave (in different pitches) and the relation of notes in a particular chord. So, all sets behave identically, and people will not be able to tell the differences between them. For another example, consider the light spectra of two sets of parallel qualia below (Figure 9.17).
Figure 9.17 Light Spectrum – Parallel Qualia
The lower panel has all qualia that have unique phenomenal characteristics that are different from those of qualia in the upper panel and that occur in only some people (so we cannot know what the lower panel’s qualia are like and cannot demonstrate them here in the picture). But all the internal relationships among qualia in each spectrum of both panels are the same. For example, the way the colors change their hues along the spectrum, the apparent brightness at all wavelengths along the spectrum, and the perceived hue differences between colors of different wavelengths (such as between the color at 440 nm vs. the one at 700 nm [which is blue vs. red in the upper panel] and between the color at 540 nm vs. the one at 590 nm [which is green vs. yellow in the upper panel]) are the same in both panels. Therefore, if this kind of parallel qualia occurs among people, people will not be able to tell that they are experiencing different qualia.
Therefore, parallel qualia can occur among people, and, behaviorally, people will not be able to tell that they are experiencing different qualia. However, it is important to note that parallel qualia are restrictedly different qualia – they cannot occur haphazardly but must occur in some restricted ways, with some rules governing their manifestations. The governing rules must be that
- The qualia are different in different people.
- The qualia must have the same number and type of their phenomenal characteristics. For example, all the visual qualia in every people must have color, brightness, shape, dimension, and velocity phenomenal characteristics. They cannot lack any of these characteristics in some people, and they cannot have more or extraordinary phenomenal characteristics in some people.
- The qualia must have all the internal relationships among qualia in every set similar to those in other sets, as discussed above.
Notably, if parallel qualia do occur, the physical problem about them is “What is the mechanism that keeps them occurring restrictedly according to these rules?”. And the philosophical question about them is “Why should qualia manifest themselves differently in only certain restricted ways, why not in a totally random way, or why not not-differently at all?”.
From all the evidence at present, it can be concluded that
– Objectively different qualia can occur.
– Completely randomly different qualia do not occur.
– Partially randomly different qualia do not occur.
– Restrictedly different qualia in some forms, such as parallel qualia, may occur, and, behaviorally, people will not be able to tell that they are experiencing different qualia.
However, theoretically, these issues can be investigated by examining signaling patterns of those different qualia, and according to Theorem VI1 and Theorem VI2, it will be found that signaling patterns of qualia of the same things under the same conditions are the same and that, because those signaling patterns are qualia, those qualia are identical and that different qualia of any kind do not occur.
Predictions about different qualia are the same as predictions for Theorem VI1 and Theorem VI2. They will be reiterated here as follows:
- Craniopagus twins who share a certain perception neural process and can access the shared neural process of the other twin will find that the quale (of some object) that occurs in his/her neural process is similar to the quale (of the same object) that occurs in the other’s neural process provided that their neural processes for that perception are similar.
- If, in the future, there is a way to connect neural processes of different persons together so that one person’s consciousness neural process can access and read the signaling pattern of a perception neural process (such as a visual perception neural process) of another person who is experiencing the same thing (such as looking at the same color), the first person will find that the quale that occurs in the second person’s perception neural process is similar to the quale that occurs in his/her perception neural process.
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