American English
American English, sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. English is the most widely spoken language in the United States and in most circumstances i ...
) or synaesthesia (
British English
British English (BrE, en-GB, or BE) is, according to Lexico, Oxford Dictionaries, "English language, English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specifically to the English language in ...
) 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
Grapheme–color synesthesia or colored grapheme synesthesia is a form of synesthesia in which an individual's perception of numerals and letters is associated with the experience of colors. Like all forms of synesthesia, grapheme–color synesth ...
or color–graphemic synesthesia, letters or numbers are perceived as inherently colored. In spatial-sequence, or
number form
:''This article refers to the neurological phenomenon. For Unicode numbers, see Number Forms.''
A number form is a mental map of numbers, which automatically and involuntarily appears whenever someone who experiences number-forms thinks of ...
synesthesia, numbers, months of the year, or days of the week elicit precise locations in space (''e.g.,'' 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'' could explain 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'', and in many cases the terminology seems to be inaccurate. A more accurate but less common term may be ''
ideasthesia
Ideasthesia (alternative spelling ideaesthesia) is a neuropsychological phenomenon in which activations of concepts (inducers) evoke perception-like sensory experiences (concurrents). The name comes from the Ancient Greek () and (), meaning 'se ...
''.
The earliest recorded case of synesthesia is attributed to the
Oxford University
Oxford () is a city in England. It is the county town and only city of Oxfordshire. In 2020, its population was estimated at 151,584. It is north-west of London, south-east of Birmingham and north-east of Bristol. The city is home to th ...
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
A metaphor is a figure of speech that, for rhetorical effect, directly refers to one thing by mentioning another. It may provide (or obscure) clarity or identify hidden similarities between two different ideas. Metaphors are often compared wi ...
. The first medical account came from German physician Georg Tobias Ludwig Sachs in 1812. The term is from the
Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...
, 'together', and , '
sensation
Sensation (psychology) refers to the processing of the senses by the sensory system.
Sensation or sensations may also refer to:
In arts and entertainment In literature
* Sensation (fiction), a fiction writing mode
* Sensation novel, a Britis ...
The Telegraph
''The Telegraph'', ''Daily Telegraph'', ''Sunday Telegraph'' and other variant names are popular names for newspapers. Newspapers with these titles include:
Australia
* ''The Telegraph'' (Adelaide), a newspaper in Adelaide, South Australia, publ ...
. Retrieved 3 December 2018
Types
There are two overall forms of synesthesia:
* projective synesthesia: seeing colors, forms, or shapes when stimulated (the widely understood version of synesthesia)
* associative synesthesia: feeling a very strong and involuntary connection between the stimulus and the sense that it triggers
For example, in
chromesthesia
Chromesthesia or sound-to-color synesthesia is a type of synesthesia in which sound involuntarily evokes an experience of color, shape, and movement. Individuals with sound-color synesthesia are consciously aware of their synesthetic color assoc ...
(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
Solomon Veniaminovich Shereshevsky (russian: Соломон Вениаминович Шерешевский; 1886 – 1 May 1958), also known simply as 'Ш' ('Sh'), 'S.', or Luria's S was a Soviet journalist and mnemonist active in the 1920s. He w ...
, experienced synesthesia that linked all five senses. Types of synesthesia are indicated by using the notation , where x is the "inducer" or trigger experience, and y is the "concurrent" or additional experience. For example, perceiving letters and numbers (collectively called
grapheme
In linguistics, a grapheme is the smallest functional unit of a writing system.
The word ''grapheme'' is derived and the suffix ''-eme'' by analogy with ''phoneme'' and other names of emic units. The study of graphemes is called '' graphemi ...
s) 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
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
Another common form of synesthesia is the association of sounds with colors. For some, everyday sounds 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
Perfect commonly refers to:
* Perfection, completeness, excellence
* Perfect (grammar), a grammatical category in some languages
Perfect may also refer to:
Film
* ''Perfect'' (1985 film), a romantic drama
* ''Perfect'' (2018 film), a science ...
because their ability to see ''and'' 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
Richard E. Cytowic is an American neurologist and author who rekindled interest in synesthesia in the 1980s and returned it to mainstream science. He was nominated for the Pulitzer Prize for his '' New York Times Magazine'' cover story about ...
, chromesthesia is "something like fireworks": voice, music, and assorted environmental sounds such as clattering dishes or dog barks trigger color and
firework
Fireworks are a class of low explosive pyrotechnic devices used for aesthetic and entertainment purposes. They are most commonly used in fireworks displays (also called a fireworks show or pyrotechnics), combining a large number of devices in ...
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. 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 ordinal sequences as points in space. 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 can also see months or dates in the space around them, but most synesthetes "see" these sequences in their mind's eye. 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".
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
Frisson ( , ; French for "shiver"), also known as aesthetic chills or psychogenic shivers is a psychophysiological response to rewarding stimuli (including music, films, stories, and rituals) that often induces a pleasurable or otherwise posi ...
, which affects approximately 50% of the population). It is one of the least common forms of synesthesia.
Ordinal linguistic personification
Ordinal-linguistic personification (OLP, or personification) 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 (). Although this form of synesthesia was documented as early as the 1890s, researchers have, until recently, paid little attention to it (see
History of synesthesia research
Synesthesia is a neurological condition in which two or more bodily senses are coupled. For example, in a form of synesthesia known as grapheme-color synesthesia, letters or numbers may be perceived as inherently colored. Historically, the most c ...
). This form of synesthesia was named "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
Misophonia is a disorder of decreased tolerance to specific sounds or their associated stimuli that has been characterized using different language and methodologies. Reactions to trigger sounds range from anger and annoyance to activating a fi ...
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
Empathy is the capacity to understand or feel what another person is experiencing from within their frame of reference, that is, the capacity to place oneself in another's position. Definitions of empathy encompass a broad range of social, co ...
levels compared to the general population. This may be related to the so-called
mirror neuron
A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another. Thus, the neuron "mirrors" the behavior of the other, as though the observer were itself acting. Such neurons ha ...
s 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
Social neuroscience is an interdisciplinary field devoted to understanding the relationship between social experiences and biological systems. Humans are fundamentally a social species, rather than solitary. As such, '' Homo sapiens'' create eme ...
'' reviewed studies with
fMRI
Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area ...
to determine if persons who experience
autonomous sensory meridian response
Autonomous sensory meridian response (ASMR) is a tingling sensation that usually begins on the scalp and moves down the back of the neck and upper spine. A pleasant form of paresthesia, it has been compared with auditory-tactile synesthesia a ...
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
Sensory overload occurs when one or more of the body's senses experiences over-stimulation from the environment. There are many environmental elements that affect an individual. Examples of these elements are urbanization, crowding, noise, mass m ...
.
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
Mental calculation consists of arithmetical calculations using only the human brain, with no help from any supplies (such as pencil and paper) or devices such as a calculator. People may use mental calculation when computing tools are not availab ...
, and more complex creative activities like producing visual art, music, and theater.
Despite the commonalities which permit the 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
vowel
A vowel is a syllabic speech sound pronounced without any stricture in the vocal tract. Vowels are one of the two principal classes of speech sounds, the other being the consonant. Vowels vary in quality, in loudness and also in quantity (leng ...
s are more strongly colored, while for others
consonant
In articulatory phonetics, a consonant is a speech sound that is articulated with complete or partial closure of the vocal tract. Examples are and pronounced with the lips; and pronounced with the front of the tongue; and pronounced wi ...
s are more strongly colored. Self-reports, interviews, and autobiographical notes by synesthetes demonstrate a great degree of variety in types of synesthesia, the 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. Whereas a non-synesthete will need to create a mnemonic device to remember a sequence (like dates in a diary), a synesthete can simply reference their spatial visualizations.
Mechanism
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 can 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
Temporal lobe epilepsy (TLE) is a chronic disorder of the nervous system which is characterized by recurrent, unprovoked focal seizures that originate in the temporal lobe of the brain and last about one or two minutes. TLE is the most common ...
, head trauma, stroke, and brain tumors. They also note that it can likewise occur during stages of
meditation
Meditation is a practice in which an individual uses a technique – such as mindfulness, or focusing the mind on a particular object, thought, or activity – to train attention and awareness, and achieve a mentally clear and emotionally calm ...
psychedelics
Psychedelics are a subclass of hallucinogenic drugs whose primary effect is to trigger non-ordinary states of consciousness (known as psychedelic experiences or "trips").Pollan, Michael (2018). ''How to Change Your Mind: What the New Science of ...
such as
LSD
Lysergic acid diethylamide (LSD), also known colloquially as acid, is a potent psychedelic drug. Effects typically include intensified thoughts, emotions, and sensory perception. At sufficiently high dosages LSD manifests primarily mental, vi ...
caffeine
Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class. It is mainly used recreationally as a cognitive enhancer, increasing alertness and attentional performance. Caffeine acts by blocking binding of adenosine to ...
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
Ideasthesia (alternative spelling ideaesthesia) is a neuropsychological phenomenon in which activations of concepts (inducers) evoke perception-like sensory experiences (concurrents). The name comes from the Ancient Greek () and (), meaning 'se ...
. 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
Understanding is a psychological process related to an abstract or physical object, such as a person, situation, or message whereby one is able to use concepts to model that object.
Understanding is a relation between the knower and an object ...
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
The mind–body problem is a philosophical debate concerning the relationship between thought and consciousness in the human mind, and the brain as part of the physical body. The debate goes beyond addressing the mere question of how mind and bo ...
and the problem of the
explanatory gap
In the philosophy of mind and consciousness, the explanatory gap is the proposed difficulty that physicalist philosophies have in explaining how physical properties give rise to the way things feel subjectively when they are experienced. It is a ...
.
Genetics
Due to the prevalence of synesthesia among the first-degree relatives of people affected, there may be a genetic basis, as indicated by the
monozygotic twins
Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...
studies showing an epigenetic component. Synesthesia might also be an
oligogenic
Oligogenic inheritance (Greek ὀλίγος – ''ὀligos'' = few, a little) describes a trait that is influenced by a few genes. Oligogenic inheritance represents an intermediate between monogenic inheritance in which a trait is determined by a ...
condition, with
locus heterogeneity Locus heterogeneity occurs when mutations at multiple genomic loci are capable of producing the same phenotype (ie. a single trait, pattern of traits, or disorder), and each individual mutation is sufficient to cause the specific phenotype independe ...
, multiple forms of inheritance, and continuous variation in gene expression. While the exact genetic loci for this trait haven't been identified, research indicates that the genetic constructs underlying synesthesia are most likely more complex than the simple X-linked mode of inheritance that early researchers believed it to be. Further, it remains uncertain as to whether synesthesia perseveres in the genetic pool because it provides a selective advantage, or because it has become a byproduct of some other useful selected trait. Women have a higher chance of developing synesthesia, as demonstrated in the UK where females are 8 times more likely to have it. As technological equipment continues to advance, the search for clearer answers regarding the genetics behind synesthesia will become more promising.
Although often termed a "neurological condition," synesthesia is not listed in either the
DSM-IV
The ''Diagnostic and Statistical Manual of Mental Disorders'' (DSM; latest edition: DSM-5-TR, published in March 2022) is a publication by the American Psychiatric Association (APA) for the classification of mental disorders using a common langu ...
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
Perfect commonly refers to:
* Perfection, completeness, excellence
* Perfect (grammar), a grammatical category in some languages
Perfect may also refer to:
Film
* ''Perfect'' (1985 film), a romantic drama
* ''Perfect'' (2018 film), a science ...
, synesthesia is simply a difference in perceptual experience.
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 the 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.
Many 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 can assign the same characteristics because that person has permanent neural associations in the brain, rather than memories of a certain object.
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
Richard E. Cytowic is an American neurologist and author who rekindled interest in synesthesia in the 1980s and returned it to mainstream science. He was nominated for the Pulitzer Prize for his '' New York Times Magazine'' cover story about ...
identifies the following diagnostic criteria for synesthesia in his ''first'' edition book. However, the criteria are different in the second book:
# Synesthesia is involuntary and automatic.
# 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.
# Synesthetic percepts are consistent and generic (i.e., simple rather than pictorial).
# Synesthesia is highly memorable.
# 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 spectrum condition.
History
The interest in colored hearing dates back to Greek antiquity when philosophers asked if the color (''chroia'', what we now call
timbre
In music, timbre ( ), also known as tone color or tone quality (from psychoacoustics), is the perceived sound quality of a musical note, sound or tone. Timbre distinguishes different types of sound production, such as choir voices and musica ...
) of music was a quantifiable quality.
Isaac Newton
Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, physicist, astronomer, alchemist, theologian, and author (described in his time as a " natural philosopher"), widely recognised as one of the grea ...
proposed that musical tones and color tones shared common frequencies, as did
Goethe
Johann Wolfgang von Goethe (28 August 1749 – 22 March 1832) was a German poet, playwright, novelist, scientist, statesman, theatre director, and critic. His works include plays, poetry, literature, and aesthetic criticism, as well as tr ...
in his book ''
Theory of Colours
''Theory of Colours'' (german: Zur Farbenlehre, links=no) is a book by Johann Wolfgang von Goethe about the poet's views on the nature of colours and how these are perceived by humans. It was published in German in 1810 and in English in 1840 ...
''. There is a long history of building
color organ
The term color organ refers to a tradition of mechanical devices built to represent sound and accompany music in a visual medium. The earliest created color organs were manual instruments based on the harpsichord design. By the 1900s they were ele ...
s such as the
clavier à lumières
The clavier à lumières ("keyboard with lights"), or tastiera per luce, as it appears in the score, was a musical instrument invented by Alexander Scriabin for use in his work '' Prometheus: Poem of Fire''. Only one version of this instrument was ...
on which to perform colored music in concert halls.
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
Gustav Theodor Fechner (; ; 19 April 1801 – 18 November 1887) was a German physicist, philosopher, and experimental psychologist. A pioneer in experimental psychology and founder of psychophysics (techniques for measuring the mind), he ins ...
, reported the first empirical survey of colored letter photisms among 73 synesthetes in 1876, followed in the 1880s by Francis Galton.
Carl Jung
Carl Gustav Jung ( ; ; 26 July 1875 – 6 June 1961) was a Swiss psychiatrist and psychoanalyst who founded analytical psychology. Jung's work has been influential in the fields of psychiatry, anthropology, archaeology, literature, phi ...
refers to "color hearing" in his Symbols of Transformation in 1912.
In the early 1920s, the
Bauhaus
The Staatliches Bauhaus (), commonly known as the Bauhaus (), was a German art school operational from 1919 to 1933 that combined crafts and the fine arts.Oxford Dictionary of Art and Artists (Oxford: Oxford University Press, 4th edn., 20 ...
teacher and musician
Gertrud Grunow Gertrud Grunow (8 July 1870 – 11 June 1944) was a German musician and educationalist who formulated theories on the relationships between sound, colour and movement and was a specialist in vocal pedagogy. She taught courses in the "theory of harmo ...
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
Arnold Schoenberg or Schönberg (, ; ; 13 September 187413 July 1951) was an Austrian-American composer, music theorist, teacher, writer, and painter. He is widely considered one of the most influential composers of the 20th century. He was as ...
(1874-1951).Bauhaus100.Curriculum. Harmonisation theory 1919-1924 Retrieved 2 December 2018 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
The cognitive revolution was an intellectual movement that began in the 1950s as an interdisciplinary study of the mind and its processes. It later became known collectively as cognitive science. The relevant areas of interchange were between th ...
made inquiry into internal subjective states respectable again, scientists returned to synesthesia. Led in the United States by Larry Marks and
Richard Cytowic
Richard E. Cytowic is an American neurologist and author who rekindled interest in synesthesia in the 1980s and returned it to mainstream science. He was nominated for the Pulitzer Prize for his '' New York Times Magazine'' cover story about ...
, and later in England by
Simon Baron-Cohen
Sir Simon Philip Baron-Cohen (born 15 August 1958) is a British clinical psychologist and professor of developmental psychopathology at the University of Cambridge. He is the director of the university's Autism Research Centre and a Fellow o ...
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, Ph.D. theses, documentary films, and even novels.
Since the rise of the Internet in the 1990s, synesthetesia began contacting one another and creating websites devoted to the condition. These rapidly grew into international organizations such as the
American Synesthesia Association
The American Synesthesia Association (ASA) is a not-for-profit academic and public society whose mission is to foster and promote the education and the advancement of knowledge of the phenomena of synesthesia, a neurological condition in which stim ...
, the
UK Synaesthesia Association
The UK Synaesthesia Association was originally conceived by Professor Simon Baron-Cohen
Sir Simon Philip Baron-Cohen (born 15 August 1958) is a British clinical psychologist and professor of developmental psychopathology at the University o ...
, 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
Solomon Veniaminovich Shereshevsky (russian: Соломон Вениаминович Шерешевский; 1886 – 1 May 1958), also known simply as 'Ш' ('Sh'), 'S.', or Luria's S was a Soviet journalist and mnemonist active in the 1920s. He w ...
, a newspaper reporter turned
mnemonist
The title mnemonist refers to an individual with the ability to remember and recall unusually long lists of data, such as unfamiliar names, lists of numbers, entries in books, etc. Some mnemonists also memorize texts such as long poems, speeches, o ...
, was discovered by Russian neuropsychologist
Alexander Luria
Alexander Romanovich Luria (russian: Алекса́ндр Рома́нович Лу́рия, p=ˈlurʲɪjə; 16 July 1902 – 14 August 1977) was a Soviet neuropsychologist, often credited as a father of modern neuropsychology. He develope ...
to have a rare fivefold form of synesthesia, of which he is the only known case. Words and text were not only associated with highly vivid visuospatial 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
Vilayanur Subramanian Ramachandran (born 10 August 1951) is an Indian-American neuroscientist. He is known for his wide-ranging experiments and theories in behavioral neurology, including the invention of the mirror box. Ramachandran is a disti ...
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
Music visualization or music visualisation, a feature found in electronic music visualizers and media player software, generates animated imagery based on a piece of music. The imagery is usually generated and rendered in real time and in a way ...
,
audiovisual art
Audiovisual art is the exploration of kinetic abstract art and music or sound set in relation to each other. It includes
visual music, abstract film, audiovisual performances and installations.
Overview
The book ''Art and the Senses'' cites t ...
,
abstract film
Abstract may refer to:
* ''Abstract'' (album), 1962 album by Joe Harriott
* Abstract of title a summary of the documents affecting title to parcel of land
* Abstract (law), a summary of a legal document
* Abstract (summary), in academic publishi ...
, and
intermedia
Intermedia is an art theory term coined in the mid-1960s by Fluxus artist Dick Higgins to describe various interdisciplinarity art activities that occur between genres, beginning in the 1960s. It was also used by John Brockman to refer to work ...
. Distinct from neuroscience, the concept of synesthesia in the arts is regarded as the simultaneous perception of multiple stimuli in one
gestalt
Gestalt may refer to:
Psychology
* Gestalt psychology, a school of psychology
* Gestalt therapy, a form of psychotherapy
* Bender Visual-Motor Gestalt Test, an assessment of development disorders
* Gestalt Practice, a practice of self-exploration ...
experience. Neurological synesthesia has been a source of inspiration for artists, composers, poets, novelists, and digital artists.
Writers
Vladimir Nabokov
Vladimir Vladimirovich Nabokov (russian: link=no, Владимир Владимирович Набоков ; 2 July 1977), also known by the pen name Vladimir Sirin (), was a Russian-American novelist, poet, translator, and entomologist. Bor ...
wrote explicitly about synesthesia in several novels.
Nabokov
Vladimir Vladimirovich Nabokov (russian: link=no, Владимир Владимирович Набоков ; 2 July 1977), also known by the pen name Vladimir Sirin (), was a Russian-American novelist, poet, translator, and entomologist. Bo ...
described his grapheme–color synesthesia at length in his autobiography, ''
Speak, Memory
''Speak, Memory'' is an autobiographical memoir by writer Vladimir Nabokov. The book includes individual essays published between 1936 and 1951 to create the first edition in 1951. Nabokov's revised and extended edition appeared in 1966.
Scop ...
'', and portrayed it in some of his characters. In addition to
Messiaen
Olivier Eugène Prosper Charles Messiaen (, ; ; 10 December 1908 – 27 April 1992) was a French composer, organist, and ornithologist who was one of the major composers of the 20th century. His music is rhythmically complex; harmonicall ...
, 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
Jean Sibelius ( ; ; born Johan Julius Christian Sibelius; 8 December 186520 September 1957) was a Finnish composer of the late Romantic and early-modern periods. He is widely regarded as his country's greatest composer, and his music is often ...
.
Daniel Tammet
Daniel Tammet (born Daniel Paul Corney; 31 January 1979) is an English writer and savant. His memoir, ''Born on a Blue Day'' (2006), is about his early life with Asperger syndrome and savant syndrome, and was named a "Best Book for Young Adu ...
wrote a book on his experiences with synesthesia called ''Born on a Blue Day''.
Joanne Harris
Joanne Michèle Sylvie Harris (born 3 July 1964) is an English-French author, best known for her novel '' Chocolat'' (1999), which was adapted the following year for the film '' Chocolat''.
Early life
Harris was born in Barnsley, Yorkshire, t ...
, author of ''Chocolat'', is a synesthete who says she experiences colors as scents. Her novel ''Blueeyedboy'' features various aspects of synesthesia.
Painters and photographers
Wassily Kandinsky
Wassily Wassilyevich Kandinsky (; rus, Василий Васильевич Кандинский, Vasiliy Vasilyevich Kandinskiy, vɐˈsʲilʲɪj vɐˈsʲilʲjɪvʲɪtɕ kɐnʲˈdʲinskʲɪj; – 13 December 1944) was a Russian painter a ...
(a synesthete) and Piet Mondrian (not a synesthete) both experimented with image–music congruence in their paintings. 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. Linda Anderson, according to NPR considered "one of the foremost living memory painters", creates with oil crayons on fine-grain sandpaper representations of the auditory-visual synaesthesia she experiences during severe migraine attacks. 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
David Hockney (born 9 July 1937) is an English painter, draftsman, printmaker, stage designer, and photographer. As an important contributor to the pop art movement of the 1960s, he is considered one of the most influential British artists o ...
perceives music as color, shape, and configuration and uses these perceptions when painting opera stage sets (though not while creating his other artworks).
Kandinsky
Wassily Wassilyevich Kandinsky (; rus, Василий Васильевич Кандинский, Vasiliy Vasilyevich Kandinskiy, vɐˈsʲilʲɪj vɐˈsʲilʲjɪvʲɪtɕ kɐnʲˈdʲinskʲɪj; – 13 December 1944) was a Russian painter a ...
combined four senses: color, hearing, touch, and smell.
Composers
Mikalojus Konstantinas Čiurlionis
Mikalojus Konstantinas Čiurlionis ( pl, Mikołaj Konstanty Czurlanis – ) was a Lithuanian painter, composer and writer.
Čiurlionis contributed to symbolism and art nouveau, and was representative of the fin de siècle epoch. He has been ...
, 1875 – 1911, was a Lithuanian painter, composer and writer. In his short life, he composed about 400 pieces of music and created about 300 paintings, as well as many literary works and poems. He perceived colors and music simultaneously. Many of his paintings bear the names of matching musical pieces: sonatas, fugues, and preludes. Čiurlionis's works have been displayed at international exhibitions in Japan, Germany, Spain, and elsewhere. His paintings were featured at "Visual Music" fest, an homage to synesthesia that included the works of Wassily Kandinsky, James McNeill Whistler, and Paul Klee, at the Museum of Contemporary Art, Los Angeles in 2005. Čiurlionis's life was depicted in the 2012 film '' Letters to Sofija'', directed by Robert Mullan.
Example matching image and music on the right:
Alexander Scriabin composed colored music that was deliberately contrived and based on the
circle of fifths
In music theory, the circle of fifths is a way of organizing the 12 chromatic pitches as a sequence of perfect fifths. (This is strictly true in the standard 12-tone equal temperament system — using a different system requires one interval of ...
, whereas Olivier Messiaen invented a new method of composition (the
modes of limited transposition Modes of limited transposition are musical modes or scales that fulfill specific criteria relating to their symmetry and the repetition of their interval groups. These scales may be transposed to all twelve notes of the chromatic scale, but at leas ...
) specifically to render his bi-directional sound–color synesthesia. For example, the red rocks of
Bryce Canyon
Bryce Canyon National Park () is an American national park located in southwestern Utah. The major feature of the park is Bryce Canyon, which despite its name, is not a canyon, but a collection of giant natural amphitheaters along the eastern ...
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.
Michael Torke
Michael Torke (; born September 22, 1961) is an American composer who writes music influenced by jazz and minimalism.
Torke was born in Milwaukee, Wisconsin, where he attended Wilson Elementary School, graduated from Wauwatosa East High School, an ...
is a contemporary example of a synesthetic composer.
Ramin Djawadi
Ramin Djawadi (, fa, رامین جوادی; born 19 July 1974) is an Iranian and German score composer. He is known for his scores for the 2008 Marvel film ''Iron Man'' and the HBO series ''Game of Thrones'', for which he was nominated for Gramm ...
, a composer best known for his work on composing the theme songs and scores for such TV series as '' Game of Thrones'', ''
Westworld
''Westworld'' is an American science fiction-thriller media franchise that began with the 1973 film ''Westworld'', written and directed by Michael Crichton. The film depicts a technologically advanced Wild-West-themed amusement park populate ...
'' and for the '' Iron Man'' movie, also has synesthesia. He says he tends to "associate colors with music, or music with colors."
British composer Daniel Liam Glyn created the classical-contemporary music project
Changing Stations
''Changing Stations'' is a classical-contemporary concept album by British composer Daniel Liam Glyn, released on 28 October 2016 via Caravan Boy Records. The album's first single, "Monday", was released to digital music retailers on 16 Septembe ...
London Underground
The London Underground (also known simply as the Underground or by its nickname the Tube) is a rapid transit system serving Greater London and some parts of the adjacent counties of Buckinghamshire, Essex and Hertfordshire in England.
The ...
, the eleven tracks featured on the album represent the eleven main tube line colours: Bakerloo, Central,
Circle
A circle is a shape consisting of all points in a plane that are at a given distance from a given point, the centre. Equivalently, it is the curve traced out by a point that moves in a plane so that its distance from a given point is con ...
,
District
A district is a type of administrative division that, in some countries, is managed by the local government. Across the world, areas known as "districts" vary greatly in size, spanning regions or county, counties, several municipality, municipa ...
Jubilee
A jubilee is a particular anniversary of an event, usually denoting the 25th, 40th, 50th, 60th, and the 70th anniversary. The term is often now used to denote the celebrations associated with the reign of a monarch after a milestone number of y ...
Victoria
Victoria most commonly refers to:
* Victoria (Australia), a state of the Commonwealth of Australia
* Victoria, British Columbia, provincial capital of British Columbia, Canada
* Victoria (mythology), Roman goddess of Victory
* Victoria, Seychelle ...
, and Waterloo and City. Each track focuses heavily on the different speeds, sounds, and mood of each line, and are composed in the
key signature
In Western musical notation, a key signature is a set of sharp (), flat (), or rarely, natural () symbols placed on the staff at the beginning of a section of music. The initial key signature in a piece is placed immediately after the clef a ...
synaesthetically assigned by Glyn with reference to the colour of the tube line on the
map
A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes.
Many maps are static, fixed to paper or some other durable medium, while others are dynamic or interactive. Although ...
.
Musicians
The producer, rapper, and fashion designer
Kanye West
Ye ( ; born Kanye Omari West ; June 8, 1977) is an American rapper, singer, songwriter, record producer, and fashion designer.
Born in Atlanta and raised in Chicago, West gained recognition as a producer for Roc-A-Fella Records in the ea ...
is a prominent interdisciplinary case. In an impromptu speech he gave during an
Ellen
Ellen is a female given name, a diminutive of Elizabeth, Eleanor, Elena and Helen. Ellen was the 609th most popular name in the U.S. and the 17th in Sweden in 2004.
People named Ellen include:
* Ellen Adarna (born 1988), Filipino actress
* Elle ...
interview, he described his condition, saying that he sees sounds, and that everything he sonically makes is a painting. Other notable synesthetes include musicians Billy Joel,
Andy Partridge
Andrew John Partridge (born 11 November 1953) is an English guitarist, singer, songwriter, and record producer who founded the rock band XTC. He and Colin Moulding each acted as a songwriter and frontman for XTC, with Partridge writing and sing ...
Billie Eilish
Billie Eilish Pirate Baird O'Connell ( ; born December 18, 2001) is an American singer-songwriter. She first gained public attention in 2015 with her debut single " Ocean Eyes", written and produced by her brother Finneas O'Connell, with whom ...
,
Brendon Urie
Brendon Boyd Urie (born April 12, 1987) is an American singer, songwriter, and musician who is best known as the lead vocalist, primary songwriter, and multi-instrumentalist of Panic! at the Disco, of which he is the only remaining member.
In ...
,
Ida Maria
Ida Maria Børli Sivertsen ( ; born 13 July 1984), better known simply as Ida Maria, is a Norwegian musician and songwriter.
Biography Early life
Maria was born and raised in Nesna. She taught herself to play guitar and began performing at loca ...
, and
Brian Chase
Brian Chase (born February 12, 1978) is an American drummer and drone musician who plays in the New York rock band Yeah Yeah Yeahs. He was ranked at #50 in Gigwise's list of ''The Greatest Drummers of All Time''. He plays drums with traditional ...
; electronic musician Richard D. James a.k.a. Aphex Twin (who claims to be inspired by
lucid dream
A lucid dream is a type of dream in which the dreamer becomes aware that they are dreaming while dreaming. During a lucid dream, the dreamer may gain some amount of control over the dream characters, narrative, or environment; however, this is ...
s as well as music); and classical pianist
Hélène Grimaud
Hélène Rose Paule Grimaud (born 7 November 1969) is a French classical pianist and the founder of the Wolf Conservation Center in South Salem, New York.
Early life and education
Grimaud was born in Aix-en-Provence, France. She described fami ...
. Musician
Kristin Hersh Kristin may refer to:
* Kristin (name), a Scandinavian form of Christine
* ''Kristin'' (TV series), a 2001 American sitcom
* Kristin Peak, Antarctica
* Kristin School
Kristin School is a private co-educational composite school located in Alb ...
The Grateful Dead
The Grateful Dead was an American rock band formed in 1965 in Palo Alto, California. The band is known for its eclectic style, which fused elements of rock, folk, country, jazz, bluegrass, blues, rock and roll, gospel, reggae, world music, ...
wrote about his experiences with synaesthesia in his autobiography ''Drumming at the Edge of Magic''. Pharrell Williams, of the groups
The Neptunes
The Neptunes are an American songwriting and production duo composed of Pharrell Williams and Chad Hugo, formed in Virginia Beach, Virginia, in 1992. Williams often provides additional vocals on records and appears in the duo's music videos ...
and N.E.R.D., also experiences synesthesia and used it as the basis of the album ''
Seeing Sounds
''Seeing Sounds'' is the third studio album by American alternative rock band N.E.R.D released June 10, 2008 on Star Trak Entertainment and Interscope Records in the United States. After ending their contract with Virgin Records in 2005, the ban ...
''. Singer/songwriter
Marina and the Diamonds
Marina Lambrini Diamandis (; el, Μαρίνα-Λαμπρινή Διαμάντη; born 10 October 1985), known mononymously as Marina (often stylised in all caps), and previously by the stage name Marina and the Diamonds, is a Welsh singer and ...
experiences music → color synesthesia and reports colored days of the week.
Artists without synesthesia
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
In music theory, the circle of fifths is a way of organizing the 12 chromatic pitches as a sequence of perfect fifths. (This is strictly true in the standard 12-tone equal temperament system — using a different system requires one interval of ...
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
The term color organ refers to a tradition of mechanical devices built to represent sound and accompany music in a visual medium. The earliest created color organs were manual instruments based on the harpsichord design. By the 1900s they were ele ...
. 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
Jean Nicolas Arthur Rimbaud (, ; 20 October 1854 – 10 November 1891) was a French poet known for his transgressive and surreal themes and for his influence on modern literature and arts, prefiguring surrealism. Born in Charleville, he start ...
and
Charles Baudelaire
Charles Pierre Baudelaire (, ; ; 9 April 1821 – 31 August 1867) was a French poet who also produced notable work as an essayist and art critic. His poems exhibit mastery in the handling of rhyme and rhythm, contain an exoticism inherited ...
wrote of synesthetic experiences, but there is no evidence they were synesthetes themselves. Baudelaire's 1857 ' introduced the notion that the senses can and should intermingle. Baudelaire participated in a hashish experiment by psychiatrist
Jacques-Joseph Moreau
Jacques-Joseph Moreau (3 June 1804 – 26 June 1884), nicknamed "Moreau de Tours", was a French psychiatrist and member of the Club des Hashischins. Moreau was the first physician to do systematic work on drugs' effects on the central nervo ...
and became interested in how the senses might affect each other. Rimbaud later wrote ''
Voyelles
"Voyelles" or "Vowels" is a sonnet in alexandrines by Arthur Rimbaud, written in 1871 but first published in 1883. Its theme is the different characters of the vowels, which it associates with those of colours. It has become one of the most st ...
'' (1871), which was perhaps more important than ' in popularizing synesthesia. He later boasted ''"J'inventais la couleur des voyelles!"'' (I invented the colors of the vowels!).
Richard Feynman
Richard Phillips Feynman (; May 11, 1918 – February 15, 1988) was an American theoretical physicist, known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, the physics of the superfl ...
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
Vladimir Vladimirovich Nabokov (russian: link=no, Владимир Владимирович Набоков ; 2 July 1977), also known by the pen name Vladimir Sirin (), was a Russian-American novelist, poet, translator, and entomologist. Bor ...
.
* Synesthesia as pathology: in which the trait is pathological. Books in this category include ''The Whole World Over'' by
Julia Glass
Julia Glass (born March 23, 1956) is an American novelist. Her debut novel, '' Three Junes'', won the National Book Award for Fiction in 2002.
.
* 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.
Literary depictions of synesthesia are criticized as often being more of a reflection of an author's interpretation of synesthesia than of the phenomenon itself.
Research
Research on synesthesia raises questions about how the brain combines information from different sensory modalities, referred to as
crossmodal Crossmodal perception or cross-modal perception is perception that involves interactions between two or more different sensory modalities. Examples include synesthesia, sensory substitution and the McGurk effect, in which vision and hearing intera ...
perception or
multisensory integration
Multisensory integration, also known as multimodal integration, is the study of how information from the different sensory modalities (such as sight, sound, touch, smell, self-motion, and taste) may be integrated by the nervous system. A coherent r ...
.
An example of this is the
bouba/kiki effect
The bouba/kiki effect is a non-arbitrary mapping between speech sounds and the visual shape of objects. It was first documented by Wolfgang Köhler in 1929 using nonsense words. The effect has been observed in American university students, Tamil ...
. In an experiment first designed by
Wolfgang Köhler
Wolfgang Köhler (21 January 1887 – 11 June 1967) was a German psychologist and phenomenologist who, like Max Wertheimer and Kurt Koffka, contributed to the creation of Gestalt psychology.
During the Nazi regime in Germany, he prote ...
, 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
Tenerife (; ; formerly spelled ''Teneriffe'') is the largest and most populous island of the Canary Islands. It is home to 43% of the total population of the archipelago. With a land area of and a population of 978,100 inhabitants as of Janu ...
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
Ideasthesia (alternative spelling ideaesthesia) is a neuropsychological phenomenon in which activations of concepts (inducers) evoke perception-like sensory experiences (concurrents). The name comes from the Ancient Greek () and (), meaning 'se ...
.
Researchers hope that the study of synesthesia will provide better understanding of
consciousness
Consciousness, at its simplest, is sentience and awareness of internal and external existence. However, the lack of definitions has led to millennia of analyses, explanations and debates by philosophers, theologians, linguisticians, and scien ...
and its
neural correlate
The neural correlates of consciousness (NCC) refer to the relationships between mental states and neural states and constitute the minimal set of neuronal events and mechanisms sufficient for a specific conscious percept. Neuroscientists use emp ...
s. In particular, synesthesia might be relevant to the philosophical problem of
qualia
In philosophy of mind, qualia ( or ; singular form: quale) are defined as individual instances of subjective, conscious experience. The term ''qualia'' derives from the Latin neuter plural form (''qualia'') of the Latin adjective '' quālis'' () ...
, 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
Ideasthesia (alternative spelling ideaesthesia) is a neuropsychological phenomenon in which activations of concepts (inducers) evoke perception-like sensory experiences (concurrents). The name comes from the Ancient Greek () and (), meaning 'se ...
, 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. These applications include sensory prosthetics, as discussed by Chaim-Meyer Scheff in "Experimental model for the study of changes in the organization of human sensory information processing through the design and testing of non-invasive prosthetic devices for sensory impaired people". IGCAPH Comput. Phys. Handicap. (36): 3–10. doi:10.1145/15711.15713. S2CID 119242
The Voice (vOICe)
Peter Meijer developed a
sensory substitution Sensory substitution is a change of the characteristics of one sensory modality into stimuli of another sensory modality.
A sensory substitution system consists of three parts: a sensor, a coupling system, and a stimulator. The sensor records stimu ...
device for the
visually impaired
Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment ...
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 (
soundscape
A soundscape is the acoustic environment as perceived by humans, in context. The term was originally coined by Michael Southworth, and popularised by R. Murray Schafer. There is a varied history of the use of soundscape depending on discipline, ...
s) 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.
See also
*
Allochiria
Allochiria is a neurological disorder in which the patient responds to stimuli presented to one side of their body as if the stimuli had been presented at the opposite side. It is associated with spatial transpositions, usually symmetrical, of s ...
*
Autonomous Sensory Meridian Response
Autonomous sensory meridian response (ASMR) is a tingling sensation that usually begins on the scalp and moves down the back of the neck and upper spine. A pleasant form of paresthesia, it has been compared with auditory-tactile synesthesia a ...
*
Fantasy prone personality
Fantasy prone personality (FPP) is a disposition or personality trait in which a person experiences a lifelong, extensive, and deep involvement in fantasy. This disposition is an attempt, at least in part, to better describe "overactive imagination ...
*
Hallucination
A hallucination is a perception in the absence of an external stimulus that has the qualities of a real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. Hallucination is a combinati ...
*
Ideasthesia
Ideasthesia (alternative spelling ideaesthesia) is a neuropsychological phenomenon in which activations of concepts (inducers) evoke perception-like sensory experiences (concurrents). The name comes from the Ancient Greek () and (), meaning 'se ...
*
Ideophone
Ideophone is a word class evoking ideas in sound imitation or onomatopoeia to express action, manner of property. Ideophone is the least common syntactic category cross-linguistically occurring mostly in African, Australian and Amerindian langua ...
Parosmia
Parosmia (from the Greek παρά ''pará'' and ὀσμή ''osmḗ'' "smell") is a dysfunctional smell detection characterized by the inability of the brain to correctly identify an odor's "natural" smell. Instead, the natural odor is usually tr ...
Sensory substitution Sensory substitution is a change of the characteristics of one sensory modality into stimuli of another sensory modality.
A sensory substitution system consists of three parts: a sensor, a coupling system, and a stimulator. The sensor records stimu ...
The Yellow Sound
''The Yellow Sound'' (in German, ''Der Gelbe Klang'') is an experimental theater piece originated by the Russian artist Wassily Kandinsky. Created in 1909, the work was first published in ''The Blue Rider Almanac'' in 1912.
''The Yellow Sound'' wa ...