Synesthesia

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Synesthesia 

Synesthesia
Other names	Synaesthesia
How someone with synesthesia might perceive certain letters and numbers. Synesthetes see characters just as others do (in whichever color actually displayed) but may simultaneously perceive colors as associated with or evoked by each one.
Specialty	Psychiatry, neurology

Synesthesia or synaesthesia is a perceptual phenomenon in which stimulation of one sensory or cognitive pathway leads to involuntary experiences in a second sensory or cognitive pathway. People who report a lifelong history of such experiences are known as synesthetes. Awareness of synesthetic perceptions varies from person to person. In one common form of synesthesia, known as grapheme–color synesthesia or color–graphemic synesthesia, letters or numbers are perceived as inherently colored. In spatial-sequence, or number form synesthesia, numbers, months of the year, or days of the week elicit precise locations in space (for example, 1980 may be "farther away" than 1990), or may appear as a three-dimensional map (clockwise or counterclockwise). Synesthetic associations can occur in any combination and any number of senses or cognitive pathways.

Little is known about how synesthesia develops. It has been suggested that synesthesia develops during childhood when children are intensively engaged with abstract concepts for the first time. This hypothesis – referred to as semantic vacuum hypothesis – explains why the most common forms of synesthesia are grapheme-color, spatial sequence and number form. These are usually the first abstract concepts that educational systems require children to learn.

Difficulties have been recognized in adequately defining synesthesia. Many different phenomena have been included in the term synesthesia ("union of the senses"), and in many cases the terminology seems to be inaccurate. A more accurate but less common term may be ideasthesia.

The earliest recorded case of synesthesia is attributed to the Oxford University academic and philosopher John Locke, who, in 1690, made a report about a blind man who said he experienced the color scarlet when he heard the sound of a trumpet. However, there is disagreement as to whether Locke described an actual instance of synesthesia or was using a metaphor. The first medical account came from German physician Georg Tobias Ludwig Sachs in 1812. The term is from the Ancient Greek σύν syn, 'together', and αἴσθησις aisthēsis, 'sensation'.

Types

There are two overall forms of synesthesia:

• projective synesthesia: people who see actual colors, forms, or shapes when stimulated (the widely understood version of synesthesia).
• associative synesthesia: people who feel a very strong and involuntary connection between the stimulus and the sense that it triggers.

For example, in chromesthesia (sound to color), a projector may hear a trumpet, and see an orange triangle in space, while an associator might hear a trumpet, and think very strongly that it sounds "orange".

Synesthesia can occur between nearly any two senses or perceptual modes, and at least one synesthete, Solomon Shereshevsky, experienced synesthesia that linked all five senses. Types of synesthesia are indicated by using the notation x → y, where x is the "inducer" or trigger experience, and y is the "concurrent" or additional experience. For example, perceiving letters and numbers (collectively called graphemes) as colored would be indicated as grapheme → color synesthesia. Similarly, when synesthetes see colors and movement as a result of hearing musical tones, it would be indicated as tone → (color, movement) synesthesia.

While nearly every logically possible combination of experiences can occur, several types are more common than others.

Grapheme-color synesthesia

From the 2009 non-fiction book Wednesday Is Indigo Blue. Note the numbers 1-12 form an upside-down clock face.

In one of the most common forms of synesthesia, individual letters of the alphabet and numbers (collectively referred to as graphemes) are "shaded" or "tinged" with a color. While different individuals usually do not report the same colors for all letters and numbers, studies with large numbers of synesthetes find some commonalities across letters (e.g., A is likely to be red).

Chromesthesia

Main article: Chromesthesia

Another common form of synesthesia is the association of sounds with colors. For some, everyday sounds such as doors opening, cars honking, or people talking can trigger seeing colors. For others, colors are triggered when musical notes or keys are being played. People with synesthesia related to music may also have perfect pitch because their ability to see/hear colors aids them in identifying notes or keys.

The colors triggered by certain sounds, and any other synesthetic visual experiences, are referred to as photisms.

According to Richard Cytowic, chromesthesia is "something like fireworks": voice, music, and assorted environmental sounds such as clattering dishes or dog barks trigger color and firework shapes that arise, move around, and then fade when the sound ends. Sound often changes the perceived hue, brightness, scintillation, and directional movement. Some individuals see music on a "screen" in front of their faces. For Deni Simon, music produces waving lines "like oscilloscope configurations – lines moving in color, often metallic with height, width and, most importantly, depth. My favorite music has lines that extend horizontally beyond the 'screen' area."

Individuals rarely agree on what color a given sound is. B flat might be orange for one person and blue for another. Composers Franz Liszt and Nikolai Rimsky-Korsakov famously disagreed on the colors of musical keys.

Spatial sequence synesthesia

Those with spatial sequence synesthesia (SSS) tend to see numerical sequences as points in space. For instance, the number 1 might be farther away and the number 2 might be closer. People with SSS may have superior memories; in one study, they were able to recall past events and memories far better and in far greater detail than those without the condition. They also see months or dates in the space around them. Some people see time like a clock above and around them.

Number form

A number form is a mental map of numbers that automatically and involuntarily appear whenever someone who experiences number-forms synesthesia thinks of numbers. These numbers might appear in different locations and the mapping changes and varies between individuals. Number forms were first documented and named in 1881 by Francis Galton in "The Visions of Sane Persons". It is suggested that this might be caused by “cross activation” of the neural pathway that connects the parietal lobes and angular gyrus. Both of these areas are involved in numerical cognition and spatial cognition respectively.

A number form from one of Francis Galton's subjects (1881). Note how the first 4 digits roughly correspond to their positions on a clock face.

Auditory-tactile synesthesia

In auditory-tactile synesthesia, certain sounds can induce sensations in parts of the body. For example, someone with auditory-tactile synesthesia may experience that hearing a specific word or sound feels like touch in one specific part of the body or may experience that certain sounds can create a sensation in the skin without being touched. Not to be confused with the milder general reaction known as frisson, which affects approx 50% of the population. It is one of the least common forms of synesthesia.

Ordinal linguistic personification

Main article: Ordinal linguistic personification

Ordinal-linguistic personification (OLP, or personification for short) is a form of synesthesia in which ordered sequences, such as ordinal numbers, week-day names, months and alphabetical letters are associated with personalities or genders (Simner & Hubbard 2006). For example, the number 2 might be a young boy with a short temper, or the letter G might be a busy mother with a kind face. Although this form of synesthesia was documented as early as the 1890s (Flournoy 1893; Calkins 1893) researchers have, until recently, paid little attention to this form (see History of synesthesia research). This form of synesthesia was named as OLP in the contemporary literature by Julia Simner and colleagues although it is now also widely recognised by the term "sequence-personality" synesthesia. Ordinal linguistic personification normally co-occurs with other forms of synesthesia such as grapheme-color synesthesia.

Misophonia

Misophonia is a neurological disorder in which negative experiences (anger, fright, hatred, disgust) are triggered by specific sounds. Cytowic suggests that misophonia is related to, or perhaps a variety of, synesthesia. Edelstein and her colleagues have compared misophonia to synesthesia in terms of connectivity between different brain regions as well as specific symptoms. They formed the hypothesis that "a pathological distortion of connections between the auditory cortex and limbic structures could cause a form of sound-emotion synesthesia." Studies suggest that individuals with misophonia have a normal hearing sensitivity level but the limbic system and autonomic nervous system are constantly in a “heightened state of arousal” where abnormal reactions to sounds will be more prevalent.

Newer studies suggest that depending on its severity, misophonia could be associated with lower cognitive control when individuals are exposed to certain associations and triggers.

It is unclear what causes misophonia. Some scientists believe it could be genetic, others believe it to be present with other additional conditions however there is not enough evidence to conclude what causes it. There are no current treatments for the condition but could be managed with different types of coping strategies. These strategies vary from person to person, some have reported the avoidance of certain situations that could trigger the reaction: mimicking the sounds, cancelling out the sounds by using different methods like earplugs, music, internal dialog and many other tactics. Most misophonics use these to “overwrite” these sounds produced by others.

Mirror-touch synesthesia

This is a form of synesthesia where individuals feel the same sensation that another person feels (such as touch). For instance, when such a synesthete observes someone being tapped on their shoulder, the synesthete involuntarily feels a tap on their own shoulder as well. People with this type of synesthesia have been shown to have higher empathy levels compared to the general population. This may be related to the so-called mirror neurons present in the motor areas of the brain, which have also been linked to empathy.

Lexical-gustatory synesthesia

This is another form of synesthesia where certain tastes are experienced when hearing words. For example, the word basketball might taste like waffles. The documentary 'Derek Tastes Of Earwax' gets its name from this phenomenon, in references to pub owner James Wannerton who experiences this particular sensation whenever he hears the name spoken. It is estimated that 0.2% of the synesthesia population has this form of synesthesia, making it the rarest form.

Kinesthetic synesthesia

Kinesthetic synesthesia is one of the rarest documented forms of synesthesia in the world. This form of synesthesia is a combination of various different types of synesthesia. Features appear similar to auditory-tactile synesthesia but sensations are not isolated to individual numbers or letters but complex systems of relationships. The result is the ability to memorize and model complex relationships between numerous variables by feeling physical sensations around the kinesthetic movement of related variables. Reports include feeling sensations in the hands or feet, coupled with visualizations of shapes or objects, when analyzing mathematical equations, physical systems, or music. In another case, a person described seeing interactions between physical shapes causing sensations in the feet when solving a math problem. Generally, those with this type of synesthesia can memorize and visualize complicated systems, and with a high degree of accuracy, predict the results of changes to the system. Examples include predicting the results of computer simulations in subjects such as quantum mechanics or fluid dynamics when results are not naturally intuitive.

Other forms

Other forms of synesthesia have been reported, but little has been done to analyze them scientifically. There are at least 80 types of synesthesia.

In August 2017 a research article in the journal Social Neuroscience reviewed studies with fMRI to determine if persons who experience autonomous sensory meridian response are experiencing a form of synesthesia. While a determination has not yet been made, there is anecdotal evidence that this may be the case, based on significant and consistent differences from the control group, in terms of functional connectivity within neural pathways. It is unclear whether this will lead to ASMR being included as a form of existing synesthesia, or if a new type will be considered.

Signs and symptoms

Some synesthetes often report that they were unaware their experiences were unusual until they realized other people did not have them, while others report feeling as if they had been keeping a secret their entire lives. The automatic and ineffable nature of a synesthetic experience means that the pairing may not seem out of the ordinary. This involuntary and consistent nature helps define synesthesia as a real experience. Most synesthetes report that their experiences are pleasant or neutral, although, in rare cases, synesthetes report that their experiences can lead to a degree of sensory overload.

Though often stereotyped in the popular media as a medical condition or neurological aberration, many synesthetes themselves do not perceive their synesthetic experiences as a handicap. On the contrary, some report it as a gift—an additional "hidden" sense—something they would not want to miss. Most synesthetes become aware of their distinctive mode of perception in their childhood. Some have learned how to apply their ability in daily life and work. Synesthetes have used their abilities in memorization of names and telephone numbers, mental arithmetic, and more complex creative activities like producing visual art, music, and theater.

Despite the commonalities which permit definition of the broad phenomenon of synesthesia, individual experiences vary in numerous ways. This variability was first noticed early in synesthesia research. Some synesthetes report that vowels are more strongly colored, while for others consonants are more strongly colored. Self reports, interviews, and autobiographical notes by synesthetes demonstrate a great degree of variety in types of synesthesia, intensity of synesthetic perceptions, awareness of the perceptual discrepancies between synesthetes and non-synesthetes, and the ways synesthesia is used in work, creative processes, and daily life.

Synesthetes are very likely to participate in creative activities. It has been suggested that individual development of perceptual and cognitive skills, in addition to one's cultural environment, produces the variety in awareness and practical use of synesthetic phenomena. Synesthesia may also give a memory advantage. In one study, conducted by Julia Simner of the University of Edinburgh, it was found that spatial sequence synesthetes have a built-in and automatic mnemonic reference. So the non-synesthete will need to create a mnemonic device to remember a sequence (like dates in a diary), but the synesthete can simply reference their spatial visualizations.

Mechanism

Regions thought to be cross-activated in grapheme-color synesthesia (green=grapheme recognition area, red=V4 color area)

As of 2015, the neurological correlates of synesthesia had not been established.

Dedicated regions of the brain are specialized for given functions. Increased cross-talk between regions specialized for different functions may account for the many types of synesthesia. For example, the additive experience of seeing color when looking at graphemes might be due to cross-activation of the grapheme-recognition area and the color area called V4 (see figure). This is supported by the fact that grapheme-color synesthetes are able to identify the color of a grapheme in their peripheral vision even when they cannot consciously identify the shape of the grapheme.

An alternative possibility is disinhibited feedback, or a reduction in the amount of inhibition along normally existing feedback pathways. Normally, excitation and inhibition are balanced. However, if normal feedback were not inhibited as usual, then signals feeding back from late stages of multi-sensory processing might influence earlier stages such that tones could activate vision. Cytowic and Eagleman find support for the disinhibition idea in the so-called acquired forms of synesthesia that occur in non-synesthetes under certain conditions: temporal lobe epilepsy, head trauma, stroke, and brain tumors. They also note that it can likewise occur during stages of meditation, deep concentration, sensory deprivation, or with use of psychedelics such as LSD or mescaline, and even, in some cases, marijuana. However, synesthetes report that common stimulants, like caffeine and cigarettes do not affect the strength of their synesthesia, nor does alcohol.

A very different theoretical approach to synesthesia is that based on ideasthesia. According to this account, synesthesia is a phenomenon mediated by the extraction of the meaning of the inducing stimulus. Thus, synesthesia may be fundamentally a semantic phenomenon. Therefore, to understand neural mechanisms of synesthesia the mechanisms of semantics and the extraction of meaning need to be understood better. This is a non-trivial issue because it is not only a question of a location in the brain at which meaning is "processed" but pertains also to the question of understanding—epitomized in e.g., the Chinese room problem. Thus, the question of the neural basis of synesthesia is deeply entrenched into the general mind–body problem and the problem of the explanatory gap.

Genetics

The genetic mechanism of synesthesia has long been debated. Due to the prevalence of synesthesia among the first-degree relatives of synesthetes, there is evidence that synesthesia might have a genetic basis, however the monozygotic twins case studies indicate there is an epigenetic component. Synesthesia might also be an oligogenic condition, with locus heterogeneity, multiple forms of inheritance (including Mendelian in some cases), and continuous variation in gene expression. It has been found that women have a higher chance of developing Synesthesia, and in the UK, females are 8 times more likely to have it than men (reasons are unknown). When people are left-handed it is inherited, and researchers have discovered that synesthetes have a higher probability of being left-handed than the general population.

Diagnosis

Although often termed a "neurological condition," synesthesia is not listed in either the DSM-IV or the ICD since it usually does not interfere with normal daily functioning. Indeed, most synesthetes report that their experiences are neutral or even pleasant. Like perfect pitch, synesthesia is simply a difference in perceptual experience.

Reaction times for answers that are congruent with a synesthete's automatic colors are shorter than those whose answers are incongruent.

Synesthesia Test Variations A number of tests exist for synesthesia. Each common type has a specific test. When testing for grapheme-color synesthesia a visual test is given. The person is shown a picture that includes black letters and numbers. A synesthete will associate the letters and numbers with a specific color. An auditory test is another way to test for synesthesia. A sound is turned on and one will either identify it with a taste, or envision shapes. The audio test correlates with chromesthesia (sounds with colors). Since people question whether or not synesthesia is tied to memory the "retest" is given. One is given a set of objects and is asked to assign colors, tastes, personalities, or more. After a period of time, the same objects are presented and the person is asked again to do the same task. The synesthete is able to assign the same characteristics, because that person has permanent neural associations in the brain, rather than memories of a certain object. The simplest approach is test-retest reliability over long periods of time, using stimuli of color names, color chips, or a computer-screen color picker providing 16.7 million choices. Synesthetes consistently score around 90% on reliability of associations, even with years between tests. In contrast, non-synesthetes score just 30–40%, even with only a few weeks between tests and a warning that they would be retested.

The automaticity of synesthetic experience. A synesthete might perceive the left panel like the panel on the right.

Grapheme-color synesthetes, as a group, share significant preferences for the color of each letter (e.g., A tends to be red; O tends to be white or black; S tends to be yellow etc.) Nonetheless, there is a great variety in types of synesthesia, and within each type, individuals report differing triggers for their sensations and differing intensities of experiences. This variety means that defining synesthesia in an individual is difficult, and the majority of synesthetes are completely unaware that their experiences have a name.

Neurologist Richard Cytowic identifies the following diagnostic criteria for synesthesia in his first edition book. However, the criteria are different in the second book:

1. Synesthesia is involuntary and automatic.
2. Synesthetic perceptions are spatially extended, meaning they often have a sense of "location." For example, synesthetes speak of "looking at" or "going to" a particular place to attend to the experience.
3. Synesthetic percepts are consistent and generic (i.e., simple rather than pictorial).
4. Synesthesia is highly memorable.
5. Synesthesia is laden with affect.

Cytowic's early cases mainly included individuals whose synesthesia was frankly projected outside the body (e.g., on a "screen" in front of one's face). Later research showed that such stark externalization occurs in a minority of synesthetes. Refining this concept, Cytowic and Eagleman differentiated between "localizers" and "non-localizers" to distinguish those synesthetes whose perceptions have a definite sense of spatial quality from those whose perceptions do not.

Prevalence

Estimates of prevalence of synesthesia have ranged widely, from 1 in 4 to 1 in 25,000 - 100,000. However, most studies have relied on synesthetes reporting themselves, introducing self-referral bias. In what is cited as the most accurate prevalence study so far, self-referral bias was avoided by studying 500 people recruited from the communities of Edinburgh and Glasgow Universities; it showed a prevalence of 4.4%, with 9 different variations of synesthesia. This study also concluded that one common form of synesthesia—grapheme-color synesthesia (colored letters and numbers) – is found in more than one percent of the population, and this latter prevalence of graphemes-color synesthesia has since been independently verified in a sample of nearly 3,000 people in the University of Edinburgh.

The most common forms of synesthesia are those that trigger colors, and the most prevalent of all is day-color. Also relatively common is grapheme-color synesthesia. We can think of "prevalence" both in terms of how common is synesthesia (or different forms of synesthesia) within the population, or how common are different forms of synesthesia within synesthetes. So within synesthetes, forms of synesthesia that trigger color also appear to be the most common forms of synesthesia with a prevalence rate of 86% within synesthetes. In another study, music-color is also prevalent at 18–41%. Some of the rarest are reported to be auditory-tactile, mirror-touch, and lexical-gustatory.

There is research to suggest that the likelihood of having synesthesia is greater in people with autism.

History

The interest in colored hearing dates back to Greek antiquity, when philosophers asked if the color (chroia, what we now call timbre) of music was a quantifiable quality. Isaac Newton proposed that musical tones and color tones shared common frequencies, as did Goethe in his book Theory of Colours. There is a long history of building color organs such as the clavier à lumières on which to perform colored music in concert halls. In further support of this notion, in Indian classical music, the musical terms raga and rasa are also synonyms for color and (quality of) taste, respectively.

The first medical description of "colored hearing" is in an 1812 thesis by the German physician Georg Tobias Ludwig Sachs. The "father of psychophysics," Gustav Fechner, reported the first empirical survey of colored letter photisms among 73 synesthetes in 1876, followed in the 1880s by Francis Galton. Carl Jung refers to "color hearing" in his Symbols of Transformation in 1912.

In the early 1920s, the Bauhaus teacher and musician Gertrud Grunow researched the relationships between sound, color and movement and developed a 'twelve-tone circle of colour' which was analogous with the twelve-tone music of the Austrian composer Arnold Schönberg (1874-1951). She was a participant in at least one of the Congresses for Colour-Sound Research (German:Kongreß für Farbe-Ton-Forschung) held in Hamburg in the late 1920s and early 1930s.

Research into synesthesia proceeded briskly in several countries, but due to the difficulties in measuring subjective experiences and the rise of behaviorism, which made the study of any subjective experience taboo, synesthesia faded into scientific oblivion between 1930 and 1980.

As the 1980s cognitive revolution made inquiry into internal subjective states respectable again, scientists returned to synesthesia. Led in the United States by Larry Marks and Richard Cytowic, and later in England by Simon Baron-Cohen and Jeffrey Gray, researchers explored the reality, consistency, and frequency of synesthetic experiences. In the late 1990s, the focus settled on grapheme → color synesthesia, one of the most common and easily studied types. Psychologists and neuroscientists study synesthesia not only for its inherent appeal, but also for the insights it may give into cognitive and perceptual processes that occur in synesthetes and non-synesthetes alike. Synesthesia is now the topic of scientific books and papers, PhD theses, documentary films, and even novels.

Since the rise of the Internet in the 1990s, synesthetes began contacting one another and creating web sites devoted to the condition. These rapidly grew into international organizations such as the American Synesthesia Association, the UK Synaesthesia Association, the Belgian Synesthesia Association, the Canadian Synesthesia Association, the German Synesthesia Association, and the Netherlands Synesthesia Web Community.

Society and culture

Notable cases

Solomon Shereshevsky, a newspaper reporter turned celebrated mnemonist, was discovered by Russian neuropsychologist, Alexander Luria, to have a rare fivefold form of synesthesia. Words and text were not only associated with highly vivid visuo-spatial imagery but also sound, taste, color, and sensation. Shereshevsky could recount endless details of many things without form, from lists of names to decades-old conversations, but he had great difficulty grasping abstract concepts. The automatic, and nearly permanent, retention of every detail due to synesthesia greatly inhibited Shereshevsky's ability to understand what he read or heard.

Neuroscientist and author V.S. Ramachandran studied the case of a grapheme-color synesthete who was also color blind. While he couldn't see certain colors with his eyes, he could still "see" those colors when looking at certain letters. Because he didn't have a name for those colors, he called them "Martian colors."

Art

Other notable synesthetes come particularly from artistic professions and backgrounds. Synesthetic art historically refers to multi-sensory experiments in the genres of visual music, music visualization, audiovisual art, abstract film, and intermedia. Distinct from neuroscience, the concept of synesthesia in the arts is regarded as the simultaneous perception of multiple stimuli in one gestalt experience.

Neurological synesthesia has been a source of inspiration for artists, composers, poets, novelists, and digital artists. Vladimir Nabokov writes explicitly about synesthesia in several novels. Wassily Kandinsky (a synesthete) and Piet Mondrian (not a synesthete) both experimented with image-music congruence in their paintings. Alexander Scriabin composed colored music that was deliberately contrived and based on the circle of fifths, whereas Olivier Messiaen invented a new method of composition (the modes of limited transposition) specifically to render his bi-directional sound-color synesthesia. For example, the red rocks of Bryce Canyon are depicted in his symphony Des canyons aux étoiles... ("From the Canyons to the Stars"). New art movements such as literary symbolism, non-figurative art, and visual music have profited from experiments with synesthetic perception and contributed to the public awareness of synesthetic and multi-sensory ways of perceiving.

Contemporary artists with synesthesia, such as Carol Steen and Marcia Smilack (a photographer who waits until she gets a synesthetic response from what she sees and then takes the picture), use their synesthesia to create their artwork. Brandy Gale, a Canadian visual artist, experiences an involuntary joining or crossing of any of her senses – hearing, vision, taste, touch, smell and movement. Gale paints from life rather than from photographs and by exploring the sensory panorama of each locale attempts to capture, select, and transmit these personal experiences.

David Hockney perceives music as color, shape, and configuration and uses these perceptions when painting opera stage sets (though not while creating his other artworks). Kandinsky combined four senses: color, hearing, touch, and smell. Nabokov described his grapheme-color synesthesia at length in his autobiography, Speak, Memory, and portrayed it in some of his characters. In addition to Messiaen, whose three types of complex colors are rendered explicitly in musical chord structures that he invented, other composers who reported synesthesia include Duke Ellington, Rimsky-Korsakov, and Jean Sibelius. Michael Torke is a contemporary example of a synesthetic composer. Physicist Richard Feynman describes his colored equations in his autobiography, What Do You Care What Other People Think?

Other notable synesthetes include musicians Billy Joel, Itzhak Perlman, Alexander Frey, Lorde, Brendon Urie, Ida Maria, Brian Chase and Patrick Stump; inventor Nikola Tesla; electronic musician Richard D. James a.k.a. Aphex Twin (who claims to be inspired by lucid dreams as well as music); and classical pianist Hélène Grimaud. Drummer Mickey Hart of The Grateful Dead wrote about his experiences with synaesthesia in his autobiography Drumming at the Edge of Magic. Pharrell Williams, of the groups The Neptunes and N.E.R.D., also experiences synesthesia and used it as the basis of the album Seeing Sounds. Singer/songwriter Marina and the Diamonds experiences music → color synesthesia and reports colored days of the week.

Some artists frequently mentioned as synesthetes did not, in fact, have the neurological condition. Scriabin's 1911 Prometheus, for example, is a deliberate contrivance whose color choices are based on the circle of fifths and appear to have been taken from Madame Blavatsky. The musical score has a separate staff marked luce whose "notes" are played on a color organ. Technical reviews appear in period volumes of Scientific American. On the other hand, his older colleague Rimsky-Korsakov (who was perceived as a fairly conservative composer) was, in fact, a synesthete.

French poets Arthur Rimbaud and Charles Baudelaire wrote of synesthetic experiences, but there is no evidence they were synesthetes themselves. Baudelaire's 1857 Correspondances introduced the notion that the senses can and should intermingle. Baudelaire participated in a hashish experiment by psychiatrist Jacques-Joseph Moreau and became interested in how the senses might affect each other. Rimbaud later wrote Voyelles (1871), which was perhaps more important than Correspondances in popularizing synesthesia. He later boasted "J'inventais la couleur des voyelles!" (I invented the colors of the vowels!).

Daniel Tammet wrote a book on his experiences with synesthesia called Born on a Blue Day.

Joanne Harris, author of Chocolat, is a synesthete who says she experiences colors as scents. Her novel Blueeyedboy features various aspects of synesthesia.

Ramin Djawadi, a composer best known for his work on composing the theme songs and scores for such TV series as Game of Thrones, Westworld and for the Iron Man movie, also has synesthesia. He says he tends to "associate colors with music, or music with colors."

Literature

Synesthesia is sometimes used as a plot device or way of developing a character's inner life. Author and synesthete Pat Duffy describes four ways in which synesthetic characters have been used in modern fiction.

• Synesthesia as Romantic ideal: in which the condition illustrates the Romantic ideal of transcending one's experience of the world. Books in this category include The Gift by Vladimir Nabokov.
• Synesthesia as pathology: in which the trait is pathological. Books in this category include The Whole World Over by Julia Glass.
• Synesthesia as Romantic pathology: in which synesthesia is pathological but also provides an avenue to the Romantic ideal of transcending quotidian experience. Books in this category include Holly Payne’s The Sound of Blue and Anna Ferrara's The Woman Who Tried To Be Normal.
• Synesthesia as psychological health and balance: Painting Ruby Tuesday by Jane Yardley, and A Mango-Shaped Space by Wendy Mass.

Many literary depictions of synesthesia are not accurate. Some say more about an author's interpretation of synesthesia than the phenomenon itself.

Research

Tests like this demonstrate that people do not attach sounds to visual shapes arbitrarily. When people are given a choice between the words "Bouba" and "Kiki", the left shape is almost always called "Kiki" while the right is called "Bouba"

Research on synesthesia raises questions about how the brain combines information from different sensory modalities, referred to as crossmodal perception or multisensory integration.

An example of this is the bouba/kiki effect. In an experiment first designed by Wolfgang Köhler, people are asked to choose which of two shapes is named bouba and which kiki. The angular shape, kiki, is chosen by 95–98% and bouba for the rounded one. Individuals on the island of Tenerife showed a similar preference between shapes called takete and maluma. Even 2.5-year-old children (too young to read) show this effect. Research indicated that in the background of this effect may operate a form of ideasthesia.

Researchers hope that the study of synesthesia will provide better understanding of consciousness and its neural correlates. In particular, synesthesia might be relevant to the philosophical problem of qualia, given that synesthetes experience extra qualia (e.g., colored sound). An important insight for qualia research may come from the findings that synesthesia has the properties of ideasthesia, which then suggest a crucial role of conceptualization processes in generating qualia.

Technological applications

Synesthesia also has a number of practical applications, one of which is the use of 'intentional synesthesia' in technology.

The Voice (vOICe)

Peter Meijer developed a sensory substitution device for the visually impaired called The vOICe (the capital letters "O," "I," and "C" in "vOICe" are intended to evoke the expression "Oh I see"). The vOICe is a privately owned research project, running without venture capital, that was first implemented using low-cost hardware in 1991. The vOICe is a visual-to-auditory sensory substitution device (SSD) preserving visual detail at high resolution (up to 25,344 pixels). The device consists of a laptop, head-mounted camera or computer camera, and headphones. The vOICe converts visual stimuli of the surroundings captured by the camera into corresponding aural representations (soundscapes) delivered to the user through headphones at a default rate of one soundscape per second. Each soundscape is a left-to-right scan, with height represented by pitch, and brightness by loudness. The vOICe compensates for the loss of vision by converting information from the lost sensory modality into stimuli in a remaining modality.

Sign (semiotics)

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Sign_(semiotics) 

In semiotics, a sign is anything that communicates a meaning that is not the sign itself to the interpreter of the sign. The meaning can be intentional such as a word uttered with a specific meaning, or unintentional, such as a symptom being a sign of a particular medical condition. Signs can communicate through any of the senses, visual, auditory, tactile, olfactory, or taste.

Two major theories describe the way signs acquire the ability to transfer information. Both theories understand the defining property of the sign as a relation between a number of elements. In the tradition of semiotics developed by Ferdinand de Saussure (referred to as semiology) the sign relation is dyadic, consisting only of a form of the sign (the signifier) and its meaning (the signified). Saussure saw this relation as being essentially arbitrary (the principle of semiotic arbitrariness), motivated only by social convention. Saussure's theory has been particularly influential in the study of linguistic signs. The other major semiotic theory, developed by C. S. Peirce, defines the sign as a triadic relation as "something that stands for something, to someone in some capacity" This means that a sign is a relation between the sign vehicle (the specific physical form of the sign), a sign object (the aspect of the world that the sign carries meaning about) and an interpretant (the meaning of the sign as understood by an interpreter). According to Peirce signs can be divided by the type of relation that holds the sign relation together as either icons, indices or symbols. Icons are those signs that signify by means of similarity between sign vehicle and sign object (e.g. a portrait, or a map), indices are those that signify by means of a direct relation of contiguity or causality between sign vehicle and sign object (e.g. a symptom), and symbols are those that signify through a law or arbitrary social convention.

Dyadic signs

According to Saussure (1857–1913), a sign is composed of the signifier (signifiant), and the signified (signifié). These cannot be conceptualized as separate entities but rather as a mapping from significant differences in sound to potential (correct) differential denotation. The Saussurean sign exists only at the level of the synchronic system, in which signs are defined by their relative and hierarchical privileges of co-occurrence. It is thus a common misreading of Saussure to take signifiers to be anything one could speak, and signifieds as things in the world. In fact, the relationship of language to parole (or speech-in-context) is and always has been a theoretical problem for linguistics (cf. Roman Jakobson's famous essay "Closing Statement: Linguistics and Poetics" et al.).

A famous thesis by Saussure states that the relationship between a sign and the real-world thing it denotes is an arbitrary one. There is not a natural relationship between a word and the object it refers to, nor is there a causal relationship between the inherent properties of the object and the nature of the sign used to denote it. For example, there is nothing about the physical quality of paper that requires denotation by the phonological sequence ‘paper’. There is, however, what Saussure called ‘relative motivation’: the possibilities of signification of a signifier are constrained by the compositionality of elements in the linguistic system (cf. Emile Benveniste's paper on the arbitrariness of the sign in the first volume of his papers on general linguistics). In other words, a word is only available to acquire a new meaning if it is identifiably different from all the other words in the language and it has no existing meaning. Structuralism was later based on this idea that it is only within a given system that one can define the distinction between the levels of system and use, or the semantic "value" of a sign.

Triadic signs

Charles Sanders Peirce (1839–1914) proposed a different theory. Unlike Saussure who approached the conceptual question from a study of linguistics and phonology, Peirce, the so-called father of the Pragmatist school of philosophy, extended the concept of sign to embrace many other forms. He considered "word" to be only one particular kind of sign, and characterized sign as any mediational means to understanding. He covered not only artificial, linguistic, and symbolic signs, but also all semblances (such as kindred sensible qualities), and all indicators (such as mechanical reactions). He counted as symbols all terms, propositions, and arguments whose interpretation is based upon convention or habit, even apart from their expression in particular languages. He held that "all this universe is perfused with signs, if it is not composed exclusively of signs". The setting of Peirce's study of signs is philosophical logic, which he defined as formal semiotic, and characterized as a normative field following esthetics and ethics, as more basic than metaphysics, and as the art of devising methods of research. He argued that, since all thought takes time, all thought is in signs, that all thought has the form of inference (even when not conscious and deliberate), and that, as inference, "logic is rooted in the social principle", since inference depends on a standpoint that, in a sense, is unlimited. The result is a theory not of language in particular, but rather of the production of meaning, and it rejects the idea of a static relationship between a sign and what it represents: its object. Peirce believed that signs are meaningful through recursive relationships that arise in sets of three.

Even when a sign represents by a resemblance or factual connection independent of interpretation, the sign is a sign only insofar as it is at least potentially interpretable by a mind and insofar as the sign is a determination of a mind or at least a quasi-mind, that functions as if it were a mind, for example in crystals and the work of bees—the focus here is on sign action in general, not on psychology, linguistics, or social studies (fields Peirce also pursued).

A sign depends on an object in a way that enables (and, in a sense, determines) an interpretation, an interpretant, to depend on the object as the sign depends on the object. The interpretant, then, is a further sign of the object, and thus enables and determines still further interpretations, further interpretant signs. The process, called semiosis, is irreducibly triadic, Peirce held, and is logically structured to perpetuate itself. It is what defines sign, object, and interpretant in general. As Jean-Jacques Nattiez (1990: 7) put it, "the process of referring effected by the sign is infinite." (Peirce used the word "determine" in the sense not of strict determinism, but of effectiveness that can vary like an influence.)

Peirce further characterized the three semiotic elements as follows:

1. Sign (or representamen): that which represents the denoted object (cf. Saussure's "signifier").
2. Object (or semiotic object): that which the sign represents (or as some put it, encodes). It can be anything thinkable, a law, a fact, or even a possibility (a semiotic object could even be fictional, such as Hamlet); those are partial objects; the total object is the universe of discourse, the totality of objects in that world to which one attributes the partial object. For example, perturbation of Pluto's orbit is a sign about Pluto, but not only about Pluto. The object may be
   1. immediate to the sign, the object as represented in the sign, or
   2. dynamic, the object as it really is, on which the immediate object is founded.
3. Interpretant (or interpretant sign): a sign's meaning or ramification as formed into a further sign by interpreting (or, as some put it, decoding) the sign. The interpretant may be:
   1. immediate to the sign, a kind of possibility, all that the sign is suited to immediately express, for instance a word's usual meaning;
   2. dynamic, that is, the meaning as formed into an actual effect, for example an individual translation or a state of agitation, or
   3. final or normal, that is, the ultimate meaning that inquiry taken far enough would be destined to reach. It is a kind of norm or ideal end, with which an actual interpretant may, at most, coincide.

Peirce explained that signs mediate between their objects and their interpretants in semiosis, the triadic process of determination. In semiosis a first is determined or influenced to be a sign by a second, as its object. The object determines the sign to determine a third as an interpretant. Firstness itself is one of Peirce's three categories of all phenomena, and is quality of feeling. Firstness is associated with a vague state of mind as feeling and a sense of the possibilities, with neither compulsion nor reflection. In semiosis the mind discerns an appearance or phenomenon, a potential sign. Secondness is reaction or resistance, a category associated with moving from possibility to determinate actuality. Here, through experience outside of and collateral to the given sign or sign system, one recalls or discovers the object the sign refers to, for example when a sign consists in a chance semblance of an absent but remembered object. It is through one's collateral experience that the object determines the sign to determine an interpretant. Thirdness is representation or mediation, the category associated with signs, generality, rule, continuity, habit-taking, and purpose. Here one forms an interpretant expressing a meaning or ramification of the sign about the object. When a second sign is considered, the initial interpretant may be confirmed, or new possible meanings may be identified. As each new sign is addressed, more interpretants, themselves signs, emerge. It can involve a mind's reading of nature, people, mathematics, anything.

Peirce generalized the communicational idea of utterance and interpretation of a sign, to cover all signs:

Admitting that connected Signs must have a Quasi-mind, it may further be declared that there can be no isolated sign. Moreover, signs require at least two Quasi-minds; a Quasi-utterer and a Quasi-interpreter; and although these two are at one (i.e., are one mind) in the sign itself, they must nevertheless be distinct. In the Sign they are, so to say, welded. Accordingly, it is not merely a fact of human Psychology, but a necessity of Logic, that every logical evolution of thought should be dialogic.

According to Nattiez, writing with Jean Molino, the tripartite definition of sign, object, and interpretant is based on the "trace" or neutral level, Saussure's "sound-image" (or "signified", thus Peirce's "representamen"). Thus, "a symbolic form...is not some 'intermediary' in a process of 'communication' that transmits the meaning intended by the author to the audience; it is instead the result of a complex process of creation (the poietic process) that has to do with the form as well as the content of the work; it is also the point of departure for a complex process of reception (the esthesic process that reconstructs a 'message'").

Molino's and Nattiez's diagram:

Poietic Process			Esthesic Process
"Producer"	→	Trace	←	Receiver

(Nattiez 1990, p. 17)

Peirce's theory of the sign therefore offered a powerful analysis of the signification system, its codes, and its processes of inference and learning—because the focus was often on natural or cultural context rather than linguistics, which only analyses usage in slow-time whereas human semiotic interaction in the real world often has a chaotic blur of language and signal exchange. Nevertheless, the implication that triadic relations are structured to perpetuate themselves leads to a level of complexity not usually experienced in the routine of message creation and interpretation. Hence, different ways of expressing the idea have developed.

Classes of triadic signs

By 1903 Peirce came to classify signs by three universal trichotomies dependent on his three categories (quality, fact, habit). He classified any sign:

1. by what stands as the sign — either (qualisign, also called a tone) a quality — or (sinsign, also called token) an individual fact — or (legisign, also called type) a rule, a habit;
2. by how the sign stands for its object — either (icon) by its own quality, such that it resembles the object, regardless of factual connection and of interpretive rule of reference — or (index) by factual connection to its object, regardless of resemblance and of interpretive rule of reference — or (symbol) by rule or habit of interpreted reference to its object, regardless of resemblance and of factual connection; and
3. by how the sign stands for its object to its interpretant — either (rheme, also called seme, such as a term) as regards quality or possibility, as if the sign were a qualisign, though it can be qualisign, sinsign, or legisign — or (dicisign, also called pheme, such as a proposition) as regards fact, as if the sign were an index, though it can be index or symbol — or (argument, also called delome) as regards rule or habit. This is the trichotomy of all signs as building blocks in an inference process.

• Any qualisign is an icon. Sinsigns include some icons and some indices. Legisigns include some icons, some indices, and all symbols.
• Any icon is a rheme. Indices (be they sinsigns or legisigns) include some rhemes and some dicisigns. Symbols include some rhemes, some dicisigns, and all arguments.

Because of those classificatory interdependences, the three trichotomies intersect to form ten (rather than 27) classes of signs. There are also various kinds of meaningful combination. Signs can be attached to one another. A photograph is an index with a meaningfully attached icon. Arguments are composed of dicisigns, and dicisigns are composed of rhemes. In order to be embodied, legisigns (types) need sinsigns (tokens) as their individual replicas or instances. A symbol depends as a sign on how it will be interpreted, regardless of resemblance or factual connection to its object; but the symbol's individual embodiment is an index to your experience of the object. A symbol is instanced by a specialized indexical sinsign. A symbol such as a sentence in a language prescribes qualities of appearance for its instances, and is itself a replica of a symbol such as a proposition apart from expression in a particular language. Peirce covered both semantic and syntactical issues in his theoretical grammar, as he sometimes called it. He regarded formal semiotic, as logic, as furthermore encompassing study of arguments (hypothetical, deductive, and inductive) and inquiry's methods including pragmatism; and as allied to but distinct from logic's pure mathematics.

Peirce sometimes referred to the “ground” of a sign. The ground is the pure abstraction of a quality. A sign's ground is the respect in which the sign represents its object, e.g. as in literal and figurative language. For example, an icon presents a characteristic or quality attributed to an object, while a symbol imputes to an object a quality either presented by an icon or symbolized so as to evoke a mental icon.

Peirce called an icon apart from a label, legend, or other index attached to it, a "hypoicon", and divided the hypoicon into three classes: (a) the image, which depends on a simple quality; (b) the diagram, whose internal relations, mainly dyadic or so taken, represent by analogy the relations in something; and (c) the metaphor, which represents the representative character of a sign by representing a parallelism in something else. A diagram can be geometric, or can consist in an array of algebraic expressions, or even in the common form "All __ is ___" which is subjectable, like any diagram, to logical or mathematical transformations. Peirce held that mathematics is done by diagrammatic thinking — observation of, and experimentation on, diagrams. Peirce developed for deductive logic a system of visual existential graphs, which continue to be researched today.

20th-century theories

It is now agreed that the effectiveness of the acts that may convert the message into text (including speaking, writing, drawing, music and physical movements) depends upon the knowledge of the sender. If the sender is not familiar with the current language, its codes and its culture, then he or she will not be able to say anything at all, whether as a visitor in a different language area or because of a medical condition such as aphasia.

Modern theories deny the Saussurian distinction between signifier and signified, and look for meaning not in the individual signs, but in their context and the framework of potential meanings that could be applied. Such theories assert that language is a collective memory or cultural history of all the different ways in which meaning has been communicated, and may to that extent, constitute all life's experiences (see Louis Hjelmslev). Hjelmslev did not consider the sign to be the smallest semiotic unit, as he believed it possible to decompose it further; instead, he considered the "internal structure of language" to be a system of figurae, a concept somewhat related to that of figure of speech, which he considered to be the ultimate semiotic unit.

This position implies that speaking is simply one more form of behaviour and changes the focus of attention from the text as language, to the text as a representation of purpose, a functional version of the author's intention. But, once the message has been transmitted, the text exists independently.

Hence, although the writers who co-operated to produce this page exist, they can only be represented by the signs actually selected and presented here. The interpretation process in the receiver's mind may attribute meanings completely different from those intended by the senders. But, why might this happen? Neither the sender nor the receiver of a text has a perfect grasp of all language. Each individual's relatively small stock of knowledge is the product of personal experience and their attitude to learning. When the audience receives the message, there will always be an excess of connotational meanings available to be applied to the particular signs in their context (no matter how relatively complete or incomplete their knowledge, the cognitive process is the same).

The first stage in understanding the message is therefore, to suspend or defer judgement until more information becomes available. At some point, the individual receiver decides which of all possible meanings represents the best possible fit. Sometimes, uncertainty may not be resolved, so meaning is indefinitely deferred, or a provisional or approximate meaning is allocated. More often, the receiver's desire for closure leads to simple meanings being attributed out of prejudices and without reference to the sender's intentions.

Postmodern theory

In critical theory, the notion of sign is used variously.

Many postmodernist theorists postulate a complete disconnection of the signifier and the signified. An 'empty' or 'floating signifier' is variously defined as a signifier with a vague, highly variable, unspecifiable or non-existent signified. Such signifiers mean different things to different people: they may stand for many or even any signifieds; they may mean whatever their interpreters want them to mean.

Ideasthesia

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Ideasthesia 

 

Example of associations between graphemes and colors that are described more accurately as ideasthesia than as synesthesia

Ideasthesia (alternative spelling ideaesthesia) is a neuroscientific phenomenon in which activations of concepts (inducers) evoke perception-like sensory experiences (concurrents). The name comes from the Ancient Greek ἰδέα (idéa) and αἴσθησις (aísthēsis), meaning "sensing concepts" or "sensing ideas". The notion was introduced by neuroscientist Danko Nikolić as an alternative explanation for a set of phenomena traditionally covered by synesthesia.

While "synesthesia" meaning "union of senses" implies the association of two sensory elements with little connection to the cognitive level, empirical evidence indicated that most phenomena linked to synesthesia are in fact induced by semantic representations. That is, the linguistic meaning of the stimulus is what is important rather than its sensory properties. In other words, while synesthesia presumes that both the trigger (inducer) and the resulting experience (concurrent) are of sensory nature, ideasthesia presumes that only the resulting experience is of sensory nature while the trigger is semantic.

Research have later extended the concept to topics other than synesthesia and as it turned out applicable to everyday perception the concept have developed into a theory of how we perceive. For example ideasthesia has been applied to the theory of art and could bear important implications in explaining human conscious experience, which, according to ideasthesia, is grounded in how we activate concepts.

Examples and evidence

A drawing by a synesthete which illustrates time unit-space synesthesia/ideasthesia. The months in a year are organized into a circle surrounding the synesthete's body, each month having a fixed location in space and a unique color.

A common example of synesthesia is the association between graphemes and colors, usually referred to as grapheme-color synesthesia. Here, letters of the alphabet are associated with vivid experiences of color. Studies have indicated that the perceived color is context-dependent and is determined by the extracted meaning of a stimulus. For example, an ambiguous stimulus '5' that can be interpreted either as 'S' or '5' will have the color associated with 'S' or with '5', depending on the context in which it is presented. If presented among numbers, it will be interpreted as '5' and will associate the respective color. If presented among letters, it will be interpreted as 'S' and will associate the respective synesthetic color.

Evidence for grapheme-color synesthesia comes also from the finding that colors can be flexibly associated to graphemes, as new meanings become assigned to those graphemes. In one study synesthetes were presented with Glagolitic letters that they have never seen before, and the meaning was acquired through a short writing exercise. The Glagolitic graphemes inherited the colors of the corresponding Latin graphemes as soon as the Glagolitic graphemes acquired the new meaning.

In another study, synesthetes were prompted to form novel synesthetic associations to graphemes never seen before. Synesthetes created those associations within minutes or seconds - which was time too short to account for creation of new physical connections between color representation and grapheme representation areas in the brain, pointing again towards ideasthesia. Although the time course is consistent with postsynaptic AMPA receptor upregulation and/or NMDA receptor coactivation, which would imply that the realtime experience is invoked at the synaptic level of analysis prior to establishment of novel wiring per se, a very intuitively appealing model.

For lexical-gustatory synesthesia evidence also points towards ideasthesia: In lexical-gustatory synesthesia, verbalisation of the stimulus is not necessary for the experience of concurrents. Instead, it is sufficient to activate the concept.

Another case of synesthesia is swimming-style synesthesia in which each swimming style is associated with a vivid experience of a color. These synesthetes do not need to perform the actual movements of a corresponding swimming style. To activate the concurrent experiences, it is sufficient to activate the concept of a swimming style (e.g., by presenting a photograph of a swimmer or simply talking about swimming).

It has been argued that grapheme-color synesthesia for geminate consonants also provides evidence for ideasthesia.

In pitch-color synesthesia, the same tone will be associated with different colors depending on how it has been named; do-sharp (i.e. di) will have colors similar to do (e.g., a reddish color) and re-flat (i.e. ra) will have color similar to that of re (e.g., yellowish), although the two classes refer to the same tone. Similar semantic associations have been found between the acoustic characteristics of vowels and the notion of size.

One-shot synesthesia: There are synesthetic experiences that can occur just once in a lifetime, and are thus dubbed one-shot synesthesia. Investigation of such cases has indicated that such unique experiences typically occur when a synesthete is involved in an intensive mental and emotional activity such as making important plans for one's future or reflecting on one's life. It has been thus concluded that this is also a form of ideasthesia.

In normal perception

Which one would be called Bouba and which Kiki? Responses are highly consistent among people. This is an example of ideasthesia as the conceptualization of the stimulus plays an important role.

Over the past decade, it has been suggested that the Bouba/Kiki phenomenon is a case of ideasthesia. Most people will agree that the star-shaped object on the left is named Kiki and the round one on the right Bouba. It has been assumed that these associations come from direct connections between visual and auditory cortices. For example, according to that hypothesis, representations of sharp inflections in the star-shaped object would be physically connected to the representations of sharp inflection in the sound of Kiki. However, Gomez et al. have shown that Kiki/Bouba associations are much richer as either word and either image is associated semantically to a number of concepts such as white or black color, feminine vs. masculine, cold vs. hot, and others. These sound-shape associations seem to be related through a large overlap between semantic networks of Kiki and star-shape on one hand, and Bouba and round-shape on the other hand. For example, both Kiki and star-shape are clever, small, thin and nervous. This indicates that behind Kiki-Bouba effect lies a rich semantic network. In other words, our sensory experience is largely determined by the meaning that we assign to stimuli. Food description and wine tasting is another domain in which ideasthetic association between flavor and other modalities such as shape may play an important role. These semantic-like relations play a role in successful marketing; the name of a product should match its other characteristics.

Implications for development of synesthesia

The concept of ideasthesia bears implications for understanding how synesthesia develops in children. Synesthetic children may associate concrete sensory-like experiences primarily to the abstract concepts that they have otherwise difficulties dealing with. Synesthesia may thus be used as a cognitive tool to cope with the abstractness of the learning materials imposed by the educational system — referred to also as a "semantic vacuum hypothesis". This hypothesis explains why the most common inducers in synesthesia are graphemes and time units — both relating to the first truly abstract ideas that a child needs to master.

Implications for art theory

The concept of ideasthesia has been often discussed in relation to art, and also used to formulate a psychological theory of art. According to the theory, we consider something to be a piece of art when experiences induced by the piece are accurately balanced with semantics induced by the same piece. Thus, a piece of art makes us both strongly think and strongly experience. Moreover, the two must be perfectly balanced such that the most salient stimulus or event is both the one that evokes strongest experiences (fear, joy, ... ) and strongest cognition (recall, memory, ...) — in other words, idea is well balanced with aesthesia.

Ideasthesia theory of art may be used for psychological studies of aesthetics. It may also help explain classificatory disputes about art as its main tenet is that experience of art can only be individual, depending on person's unique knowledge, experiences and history. There could exist no general classification of art satisfactorily applicable to each and all individuals.

Neurophysiology of ideasthesia

Ideasthesia is congruent with the theory of brain functioning known as practopoiesis. According to that theory, concepts are not an emergent property of highly developed, specialized neuronal networks in the brain, as is usually assumed; rather, concepts are proposed to be fundamental to the very adaptive principles by which living systems and the brain operate.

A study using magnetoencephalography has shown that the information on synesthetic colors is available in the brain signals only about 200 milliseconds after the stimulus, which is consistent with conceptual mediation. The study supports the idea that synesthesia is a semantic phenomenon—i.e., ideasthesia.

Explanatory gap

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https://en.wikipedia.org/wiki/Explanatory_gap 

In philosophy of mind and consciousness, the explanatory gap is the difficulty that physicalist theories have in explaining how physical properties give rise to the way things feel when they are experienced. It is a term introduced by philosopher Joseph Levine. In the 1983 paper in which he first used the term, he used as an example the sentence, "Pain is the firing of C fibers", pointing out that while it might be valid in a physiological sense, it does not help us to understand how pain feels.

The explanatory gap has vexed and intrigued philosophers and AI researchers alike for decades and caused considerable debate. Bridging this gap (that is, finding a satisfying mechanistic explanation for experience and qualia) is known as "the hard problem".

To take an example of a phenomenon in which there is no gap, a modern computer's behavior can be adequately explained by its physical components alone, such as its circuitry and software.In contrast, it is thought by many mind-body dualists (e.g. René Descartes, David Chalmers) that subjective conscious experience constitutes a separate effect that demands another cause that is either outside the physical world (dualism) or due to an as yet unknown physical phenomenon (see for instance quantum mind, indirect realism).

Proponents of dualism claim that the mind is substantially and qualitatively different from the brain and that the existence of something metaphysically extra-physical is required to "fill the gap". Similarly, some argue that there are further facts—facts that do not follow logically from the physical facts of the world—about conscious experience. For example, they argue that what it is like to experience seeing red does not follow logically from the physical facts of the world.

Implications

The nature of the explanatory gap has been the subject of some debate. For example, some consider it to simply be a limit on our current explanatory ability. They argue that future findings in neuroscience or future work from philosophers could close the gap. However, others have taken a stronger position and argued that the gap is a definite limit on our cognitive abilities as humans—no amount of further information will allow us to close it. There has also been no consensus regarding what metaphysical conclusions the existence of the gap provides. Those wishing to use its existence to support dualism have often taken the position that an epistemic gap—particularly if it is a definite limit on our cognitive abilities—necessarily entails a metaphysical gap.

Levine and others have wished to either remain silent on the matter or argue that no such metaphysical conclusion should be drawn. He agrees that conceivability (as used in the Zombie and inverted spectrum arguments) is flawed as a means of establishing metaphysical realities; but he points out that even if we come to the metaphysical conclusion that qualia are physical, they still present an explanatory problem.

While I think this materialist response is right in the end, it does not suffice to put the mind-body problem to rest. Even if conceivability considerations do not establish that the mind is in fact distinct from the body, or that mental properties are metaphysically irreducible to physical properties, still they do demonstrate that we lack an explanation of the mental in terms of the physical.

However, such an epistemological or explanatory problem might indicate an underlying metaphysical issue—the non-physicality of qualia, even if not proven by conceivability arguments is far from ruled out.

In the end, we are right back where we started. The explanatory gap argument doesn't demonstrate a gap in nature, but a gap in our understanding of nature. Of course a plausible explanation for there being a gap in our understanding of nature is that there is a genuine gap in nature. But so long as we have countervailing reasons for doubting the latter, we have to look elsewhere for an explanation of the former.

At the core of the problem, according to Levine, is our lack of understanding of what it means for a qualitative experience to be fully comprehended. He emphasizes that we don't even know to what extent it is appropriate to inquire into the nature of this kind of experience. He uses the laws of gravity as an example, which laws seem to explain gravity completely yet do not account for the gravitational constant. Similarly to the way in which gravity appears to be an inexplicable brute fact of nature, the case of qualia may be one in which we are either lacking essential information or in which we're exploring a natural phenomenon that simply is not further apprehensible. Levine suggests that, as qualitative experience of a physical or functional state may simply be such a brute fact, perhaps we should consider whether or not it is really necessary to find a more complete explanation of qualitative experience.

Levine points out that the solution to the problem of understanding how much there is to be known about qualitative experience seems even more difficult because we also lack a way to articulate what it means for actualities to be knowable in the manner that he has in mind. He does conclude that there are good reasons why we wish for a more complete explanation of qualitative experiences. One very significant reason is that consciousness appears to only manifest where mentality is demonstrated in physical systems that are quite highly organized. This, of course, may be indicative of a human capacity for reasoning that is no more than the result of organized functions. Levine expresses that it seems counterintuitive to accept this implication that the human brain, so highly organized as it is, could be no more than a routine executor. He notes that although, at minimum, Materialism appears to entail reducibility of anything that is not physically primary to an explanation of its dependence on a mechanism that can be described in terms of physical fundamentals, that kind of reductionism doesn't attempt to reduce psychology to physical science. However, it still entails that there are inexplicable classes of facts which are not treated as relevant to statements pertinent to psychology.