Chromesthesia

{{Short description|Sound to color synesthesia}} {{Use American English|date = February 2019}} thumb|right|200px|A keyboard depicting note-color associations. The colors are experienced with the sounding of the note, and are not necessarily localized to piano keys. '''Chromesthesia''' or '''sound-to-color synesthesia''' is a type of synesthesia in which sound involuntarily evokes an experience of color, shape, and movement.<ref name=":0">{{cite book |last=Cytowic |first=Richard E. | name-list-style = vanc |title=Synesthesia |publisher=MIT Press |year=2018 |isbn=978-0-262-53509-0 |location=Cambridge, MA }}</ref><ref name="Cytowic">{{cite book | last1 = Cytowic | first1 = Richard E | last2 = Eagleman | first2 = David M | name-list-style = vanc | date = 2009 | title = Wednesday is Indigo Blue: Discovering the Brain of Synesthesia (with an afterword by Dmitri Nabokov) | location = Cambridge | publisher = MIT Press | pages = 309 | isbn = 978-0-262-01279-9 }}</ref> Individuals with sound-color synesthesia are consciously aware of their synesthetic color associations/perceptions in daily life.<ref name="Simner">{{cite journal | vauthors = Simner J | title = Defining synaesthesia | journal = British Journal of Psychology | location = London, England | volume = 103 | issue = 1 | pages = 1–15 | date = February 2012 | pmid = 22229768 | doi = 10.1348/000712610X528305 | s2cid = 9038571 | url = https://www.pure.ed.ac.uk/ws/files/12435588/Defining_synaesthesia.pdf }}</ref> Synesthetes that perceive color while listening to music experience the colors in addition to the normal auditory sensations. The synesthetic color experience supplements, but does not obscure real, modality-specific perceptions.<ref name="Simner" /> As with other forms of synesthesia, individuals with sound-color synesthesia perceive it spontaneously, without effort, and as their normal realm of experience.<ref name="Simner" /> Chromesthesia can be induced by different auditory experiences, such as music, phonemes, speech, and/or everyday sounds.<ref name=":0" />

==Individual variance== The color associations, that is, which color is associated to which sound, tone, pitch, or timbre is highly idiosyncratic, but in most cases, consistent over time.<ref name = "Cytowic"/><ref name = "Head">{{cite journal | vauthors = de Thornley Head P | title = Synaesthesia: pitch-colour isomorphism in RGB-space? | journal = Cortex; A Journal Devoted to the Study of the Nervous System and Behavior | volume = 42 | issue = 2 | pages = 164–74 | date = February 2006 | pmid = 16683490 | doi = 10.1016/s0010-9452(08)70341-1 | s2cid = 53179317 }}</ref> Individuals with synesthesia have unique color pairings. However, studies to date have reported that synesthetes and non-synesthetes alike associate high pitched sounds with lighter or brighter colors and low pitched sounds with darker colors, indicating that a common mechanism may underlie those associations in normal adult brains.<ref name = "Ward">{{cite journal | vauthors = Ward J, Huckstep B, Tsakanikos E | title = Sound-colour synaesthesia: to what extent does it use cross-modal mechanisms common to us all? | journal = Cortex; A Journal Devoted to the Study of the Nervous System and Behavior | volume = 42 | issue = 2 | pages = 264–80 | date = February 2006 | pmid = 16683501 | doi = 10.1016/s0010-9452(08)70352-6 | s2cid = 4481009 }}</ref> There are forms of pseudo-chromesthesia that may be explained by associations synesthetes have made and forgotten from childhood.<ref>{{cite journal|title = A Statistical Study of Pseudo-Chromesthesia and of Mental-Forms|jstor = 1411912|journal = The American Journal of Psychology|date = 1893-07-01|pages = 439–464|volume = 5|issue = 4|doi = 10.2307/1411912|first = Mary Whiton|last = Calkins | name-list-style = vanc }}</ref>

As with other types of synesthesia, sound-color synesthesia can be divided into groups based on the way the colors are experienced. Those that 'see' or perceive the color in external space are called projectors, and those that perceive the color in the mind's eye are often called associators, but these terms can be misleading to understanding the nature of the experience.<ref name = "Cytowic"/><ref name = "Simner"/> For most synesthetes, the condition is not wholly sensory/perceptual.<ref name = "Simner"/>

For some individuals, chromesthesia is only triggered by speech sounds, while others' chromesthesia can be triggered by any auditory stimuli.<ref name = "Goller">{{cite journal | vauthors = Goller AI, Otten LJ, Ward J | s2cid = 17434150 | title = Seeing sounds and hearing colors: an event-related potential study of auditory-visual synesthesia | journal = Journal of Cognitive Neuroscience | volume = 21 | issue = 10 | pages = 1869–81 | date = October 2009 | pmid = 18823243 | doi = 10.1162/jocn.2009.21134 | doi-access = free }}</ref> In a study investigating variability within categories of synesthesia, 40% of subjects with chromesthesia for spoken words reported that voice pitch, accent, and prosody influenced the synesthetic color, whereas few subjects reported that volume or speed of talking had any influence.<ref name = "Van Leeuwen">{{cite journal | vauthors = Niccolai V, Jennes J, Stoerig P, Van Leeuwen TM | title = Modality and variability of synesthetic experience | journal = The American Journal of Psychology | volume = 125 | issue = 1 | pages = 81–94 | date = 2012 | pmid = 22428428 | doi = 10.5406/amerjpsyc.125.1.0081 }}</ref> Within these subjects, many reported that the speaker's emotional inflection could influence the synesthetic color, but only two reported that their own mood had such influence.<ref name = "Van Leeuwen"/> Of participants categorized as having synesthesia for music in this study, 75% reported concurrents exclusively when listening to notes being played.<ref name = "Van Leeuwen"/> When asked whether the experience of the concurrent could be voluntarily controlled, only 33% of participants indicated an ability to smother, ignore, or willfully evoke their concurrents without great effort.<ref name = "Van Leeuwen"/> Attention to the inducing stimulus was reported as influential in 59% of participants.<ref name = "Van Leeuwen"/> Other contributing factors included concentration level, fatigue, sleep habits, fever, emotions, and substances, such as caffeine or alcohol.<ref name = "Van Leeuwen"/>

Sound-color synesthesia is far more common than color-sound synesthesia, although there are reported cases where sounds and colors activate bidirectionally. One individual sees colors when she hears sounds and also hears sounds when she sees colors.<ref name = "Goller"/> This type of synesthesia interferes greatly with daily life. This individual's associations were highly consistent over time, but the associations were not necessarily the same in either direction.<ref name = "Goller"/> Another individual who had absolute pitch, as well as Chromesthesia, claimed that her absolute pitch was less stable than her Chromesthesia.<ref>{{Cite journal|last1=Haack|first1=Paul A.|last2=Radocy|first2=Rudolf E.|date=1981-07-01|title=A Case Study of a Chromesthetic|journal=Journal of Research in Music Education|language=en|volume=29|issue=2|pages=85–90|doi=10.2307/3345016|jstor=3345016|s2cid=144842634|issn=0022-4294}}</ref>

There may be an effect of semantic mediation in some individuals with sound-color synesthesia. One subject self-triggered notes on a synthesizer and noted the color associations. When the synthesizer was transposed without her knowledge, she reported identical color associations to the notes that she believed she was hearing, rather than the absolute pitch of the tones.<ref name = "Head"/>

== History == {{See also|History of synesthesia research}}

The terms synesthesia and chromesthesia have developed and evolved considerably throughout history. The first documented synesthete was Georg Tobias Ludwig Sachs in 1812.<ref name=":1">{{cite journal | vauthors = Jewanski J, Simner J, Day SA, Rothen N, Ward J | title = The evolution of the concept of synesthesia in the nineteenth century as revealed through the history of its name | journal = Journal of the History of the Neurosciences | pages = 259–285 | date = November 2019 | volume = 29 | issue = 3 | pmid = 31702956 | doi = 10.1080/0964704X.2019.1675422 | pmc = 7446036 | doi-access = free }}</ref> Although he did not give a specific name to his experience, in a medical dissertation regarding his albinism (written in Latin), he mentioned ''obscure ideas'' and described how ''colored ideas appeared to him.'' <ref>{{cite journal | vauthors = Jewanski J, Day SA, Ward J | title = A colorful albino: the first documented case of synaesthesia, by Georg Tobias Ludwig Sachs in 1812 | journal = Journal of the History of the Neurosciences | volume = 18 | issue = 3 | pages = 293–303 | date = July 2009 | pmid = 20183209 | doi = 10.1080/09647040802431946 | s2cid = 8641750 }}</ref> Even earlier than Sachs, however, Johann Gottfried Herder discussed similar ideas in his ''Treatise on the Origin of Language'' in 1772.<ref name=":1" /> He talked about how people, "through a sudden onset immediately associate with this sound that color".<ref>{{cite book | chapter=Treatise on the Origin of Language (1772)|date=2002-09-05|chapter-url=https://www.cambridge.org/core/product/identifier/CBO9781139164634A014/type/book_part| title = Herder: Philosophical Writings|pages=65–164|editor-last=Forster|editor-first=Michael N. | name-list-style = vanc |edition=1st |publisher=Cambridge University Press|doi=10.1017/cbo9781139164634.007|isbn=978-0-521-79088-8|access-date=2020-06-22}}</ref>

The first concrete term associated with chromesthesia was given by Charles-Auguste-Édouard Cornaz in an eye disease dissertation in 1848. Color blindness was a common condition known as ''chromatodysopsia'' and, since Cornaz saw chromesthesia as the opposite, he named it ''hyperchromatopsia'' or perception of too many colors.<ref name=":1" />

In 1881, Eugen Bleuler and Karl Bernhard Lehmann were the first to establish six different types of what they called ''secondary sensations'' or ''secondary imaginations.''<ref name=":1" /> The first, which was the most common, was ''sound photisms.'' They described it as "light, color, and form sensations which are elicited through hearing".<ref>{{cite journal|date=May 1881 |title=Zwangsmässige Lichtempfindungen durch Schall und verwandte Erscheinungen auf dem Gebiete der anderen Sinnesempfindungen|journal=Nature|volume=24|issue=603|pages=51–52|doi=10.1038/024051a0|bibcode=1881Natur..24...51.|issn=0028-0836|s2cid=43201081}}</ref> Their book was reviewed by an Austrian newspaper, where the term ''colored hearing,'' still commonly used today to describe chromesthesia, first appeared.<ref name=":1" />

Research on synesthesia in the United States began in 1892. And, since 1895, the term finally expanded from pure sound-to-color experiences (chromesthesia) to a wide range of phenomena, including grapheme-color synesthesia, mirror-touch synesthesia, and lexical-gustatory synesthesia.<ref name=":1" /> The rise of behaviorism between 1920 and 1940 resulted in a considerable decline in interest for synesthesia,<ref name=":0" /> as it was seen as "little more than a learned association".<ref name=":2">{{cite journal | vauthors = Ward J | title = Synesthesia | journal = Annual Review of Psychology | volume = 64 | issue = 1 | pages = 49–75 | date = 2013-01-03 | pmid = 22747246 | doi = 10.1146/annurev-psych-113011-143840 | s2cid = 241155101 }}</ref> The number of scientific papers on the topic rebounded around 1980 <ref name=":0" /> and exponentially increased in the 21st century, where substantial progress has been made to study it empirically and understand the mechanisms at work.<ref name=":2" />

== Mechanisms == Synesthesia is established in early childhood, when the brain is most plastic. There is a genetic predisposition for the condition, but the specific type is determined by environment and learning, which explains why "mappings differ across individuals, but are not strictly random".<ref name=":0" /> Furthermore, it manifests as the dominant process in distributed systems, or neural networks, which are dynamic, auto-assemble and self-calibrate.<ref name=":0" /> That is what is understood so far, but the specific mechanisms by which synesthesia occurs are still unclear and a general consensus has not yet been reached. There are two main hypotheses: Cross-activation theory and Disinhibited feedback model.<ref name=":5">{{cite journal | vauthors = Zdzinski SF, Ireland SJ, Wuttke BC, Belen KE, Olesen BC, Doyle JL, Russell BE |title=An Exploratory Neuropsychological Case Study of Two Chromesthetic Musicians | journal = Research Perspectives in Music Education | date = February 2019 | volume = 20 | issue = 1 | pages = 65–82 |url=https://www.ingentaconnect.com/content/fmea/rpme/2019/00000020/00000001/art00005 }}</ref>

===Cross-activation theory=== The cross-activation theory of synesthesia was formulated by V.S. Ramachandran and E.M. Hubard, based on converging evidence from studies of synesthesia that sensory areas for processing real and synesthetic information tend to be neighboring brain regions.<ref name="Specht">{{cite journal | vauthors = Specht K | s2cid = 143228367 | title = Synaesthesia: cross activations, high interconnectivity, and a parietal hub. | journal = Translational Neuroscience | date = March 2012 | volume = 3 | issue = 1 | pages = 15–21 | doi = 10.2478/s13380-012-0007-z | doi-access = free }}</ref> This is most apparent in grapheme-color synesthesia, because the brain regions for color processing and visual word form processing are adjacent.<ref name="Brang">{{cite journal | vauthors = Brang D, Williams LE, Ramachandran VS | s2cid = 10497638 | title = Grapheme-color synesthetes show enhanced crossmodal processing between auditory and visual modalities | journal = Cortex; A Journal Devoted to the Study of the Nervous System and Behavior | volume = 48 | issue = 5 | pages = 630–7 | date = May 2012 | pmid = 21763646 | doi = 10.1016/j.cortex.2011.06.008 }}</ref> Individuals with chromesthesia show activation of brain areas involved in visual processing, such as V4, immediately after the auditory perception, indicating an automatic linking of sounds and colors.<ref name="Specht" />

Neonates have increased connectivity between different brain areas, but these hyper-connections are cut back during development.<ref name=":0" /> The reason for this cross-activation is unclear, but one hypothesis is that the increased connectivity between adjacent brain regions is due to a reduction in the pruning of neuronal networks during childhood.<ref name="Specht" /> Another hypothesis is that unusual branching of neurons causes more numerous synaptic connections and cross-activation. These hypotheses align with Daphne Maurer's neonatal hypothesis, which states that all newborns are synesthetes, but the condition disappears at around the age of three months.<ref name=":0" />

Cross-activation may occur at the fusiform gyrus in projector synesthetes (who perceive photisms in external space) and at the angular gyrus in associator synesthetes (who perceive photisms, which come from learned associations, in their mind).<ref name=":5" />

One problem with the cross-activation theory is that synesthesia should be present from birth, but is only evident from mid-childhood.<ref name=":0" />

===Disinhibited feedback model=== The disinhibited feedback model is an alternative to the cross-activation theory.<ref name="Specht" /> The disinhibited feedback model rejects the assumption of increased connectivity in synesthetes and proposes that the cross-activation is due to a decrease of inhibition in the networks present in the normal adult brain.<ref name="Specht" /> Disinhibited feedback could account for the fact that chromesthesia can be acquired by damage to the retino-cortical pathway <ref name="Ward" /> or transiently induced through chemical agents, sensory deprivation, meditation, etc.<ref name=":0" />

In all brains, there are anatomical cross-connections where inhibition and excitation are counterbalanced.<ref name=":0" /> However, excitation prevails in synesthetes and this disinhibits other structures "to elicit sensory sensations in a second sensory area".<ref name=":5" /> One theory that explains how this occurs is neurotransmitter-mediated inhibition. Local inhibitory networks are supposed to confine cortical firing to a specific region, but it leads to a spread of cortical firing, when these networks are blocked by bicuculline.<ref name=":0" />

Forward feeding connections in the brain that receive converging signals from multiple pathways are reciprocated by feedback connections.<ref name="Grossenbacher">{{cite journal | vauthors = Grossenbacher PG, Lovelace CT | title = Mechanisms of synesthesia: cognitive and physiological constraints | journal = Trends in Cognitive Sciences | volume = 5 | issue = 1 | pages = 36–41 | date = January 2001 | pmid = 11164734 | doi = 10.1016/s1364-6613(00)01571-0 | s2cid = 15092606 }}</ref> In most people, feedback connections are sufficiently inhibited to avoid synesthetic induction of a concurrent perception. In synesthetes, it is suggested that feedforward signaling in the inducer pathway could activate neurons, to which both inducer and concurrent pathways converge, and that feedback signaling is capable of propagating down the concurrent pathway to activate the concurrent representation.<ref name="Grossenbacher" /> In this mechanism, feedforward activity from the inducer leads to feedback activation of the concurrent representation.<ref name="Grossenbacher" />

==Research== The mechanism by which synesthesia occurs has yet to be identified. Given that synesthetes and non-synesthetes both match sounds to colors in a non-arbitrary way and that the ingestion of hallucinogenic drugs can induce synesthesia in under an hour, some researchers suggest that synesthetic experience uses existing pathways in the normal brain.<ref name = "Ward"/> The cause of synesthesia is also unclear, although evidence points to a genetic predisposition. Synesthesia runs in families, though the condition may present idiosyncratically within a family.<ref name = "Specht"/> Synesthesia may skip a generation.<ref name = "Specht"/> However, there are cases of monozygotic twins where only one has synesthesia, indicating there may be additional factors.<ref name = "Specht"/>

Differences between synesthetic and non-synesthetic brains may reflect direct hard-wired connections between unimodal auditory and visual regions in the brain, or they may reflect feedback pathways from multimodal audiovisual regions to unimodal visual regions present in all brains.<ref name = "Ward"/>

===Involvement of specific brain regions=== In addition to high interconnectivity in synesthesia, there is an apparent contribution from the inferior parietal cortex during synesthetic experiences, possibly serving as the mechanism to bind the real and synesthetic perceptions into one experience.<ref name = "Specht"/><ref name = "Dovern">{{cite journal | vauthors = Dovern A, Fink GR, Fromme AC, Wohlschläger AM, Weiss PH, Riedl V | title = Intrinsic network connectivity reflects consistency of synesthetic experiences | journal = The Journal of Neuroscience | volume = 32 | issue = 22 | pages = 7614–21 | date = May 2012 | pmid = 22649240 | pmc = 6703581 | doi = 10.1523/JNEUROSCI.5401-11.2012 }}</ref> Parietal lobe activation is most apparent when the synesthete is directing attentional focus to the synesthetic experience.<ref name = "Specht"/>

Functional magnetic resonance imaging studies implicate the left superior temporal sulcus for the integration of auditory and visual information. This brain region responds most strongly to congruent pairs of visual and auditory information, such as congruent lip movements and speech.<ref name = "Ward"/>

===Definitional bias=== The literature contains conflicting definitional criteria for synesthesia, which could bias selection of research subjects and interpretation of results. Synesthesia has long been described as a 'merging of the senses' or as a kind of 'cross-sensory' experience; however, the condition is not purely sensory/perceptual in all individuals. While this description of synesthesia is useful in describing the condition, it should not be interpreted literally and used as selection criteria for scientific exploration.<ref name = "Simner"/>

Another common defining characteristic of synesthesia is that synesthetic associations are consistent over time. This is generally determined by having individuals report color pairings twice, with several months separating the test from the re-test. Consistency has been described as so fundamental to synesthesia that the test of consistency has become the behavioral 'gold standard' for identifying the genuine condition, and selecting subjects for research.<ref name = "Simner"/> This creates a circular bias, in which virtually all research subjects show consistency over time because they have been selected for it.<ref name = "Simner"/> While consistency, to some extent, may be characteristic of synesthesia, there are individuals that fit all other criteria of synesthesia, but report that their synesthetic associations are not consistent over time.<ref name = "Simner"/>

Another misleading defining characteristic of synesthesia has been that synesthetic concurrents are spatially extended, and the individuals should be able to indicate a spatial location in which the concurrent is experienced. In the case of sound-color synesthesia, those who experience colored photisms from listening to music can often describe the direction of movement of these photisms.<ref name = "Simner"/> While the majority of synesthetes experience a spatial quality to the synesthetic experience, there are still many that report no such quality.<ref name = "Simner"/>

In addition to definitional inclusion/exclusion criteria for synesthesia research, self-report bias is also likely relevant to many studies. This self-report bias, if it exists, would perpetuate itself because the condition would become defined by those cases that become known, and not by those that remain hidden.<ref name = "Simner"/> This is significant because many synesthetic individuals may exclude themselves on the basis of not fitting the prescribed definitional criteria. This is also significant to the extent that synesthetic individuals have a limited ability to differentiate their experience from that of nonsynesthetic individuals.

A possible resolution of these issues would involve defining synesthesia on a neurological basis.<ref name = "Simner"/> Such a unifying neurobiological cause has yet to be found, but if it exists, it would deepen understanding of the phenomenon in ways that the behavioral definition has failed to do.<ref name = "Simner"/>

== Drug-induced chromesthesia == [[File:Sketch of Jacques-Joseph Moreau by Théophile Gautier (1845).jpg|thumb|Gautier, under the influence of hashish, depicted his chromesthetic perceptions over the piano as lines of color arising from the music.]] Chromesthesia can be transiently induced with chemical agents through the manipulation of neurotransmitters. These substances can also modulate existing synesthesia.<ref name=":0" /> Psychoactive drugs including LSD, mescaline, psilocybin, and ayahuasca are non-selective serotonin agonists that elicit spontaneous synesthesia, specially sound-to-color.<ref name=":3">{{cite journal | vauthors = Luke DP, Terhune DB | title = The induction of synaesthesia with chemical agents: a systematic review | journal = Frontiers in Psychology | volume = 4 | pages = 753 | date = October 2013 | pmid = 24146659 | pmc = 3797969 | doi = 10.3389/fpsyg.2013.00753 | doi-access = free }}</ref>

The first to report drug-induced chromesthesia was Théophile Gautier in 1845.<ref name=":0" /> Under the influence of hashish, he described: "My hearing was developed extraordinarily; I heard the noise of colors. Green, red, blue, yellow sounds reached me in perfectly distinguishable waves".<ref name=":4">{{cite web | first = Crétien | last = van Campen | name-list-style = vanc |date=2019-09-09|title=Exploring Drug-Induced Synesthesia|url=https://thereader.mitpress.mit.edu/exploring-drug-induced-synesthesia/|access-date=2020-06-23| work = The MIT Press Reader|language=en}}</ref> Gautier made a sketch of Gustave Moreau playing the piano, where he depicted his chromesthetic experiences as lines of color above the instrument.<ref name=":4" />

Recent scientific studies, with enhanced methodologies, suggest that drug-induced synesthesia is substantially different from congenital synesthesia. Psychoactive substances "affect ongoing streams of transmission rather than causing stimulus-induced activation".<ref name=":0" /> The most common type of synesthesia elicited with chemical agents is chromesthesia. Still, frequent inducers include auditory and visual stimuli, especially music - which could explain the prevalence of sound-to-color synesthesia over other types of synesthesia.<ref name=":3" /> [[File:Klüver's Form Constants.jpg|thumb|Heinrich Klüver's form constants: Tunnels, Spirals, Honeycombs Gratings, and Cobwebs]] Heinrich Klüver categorized recurring geometric shapes under the influence of peyote in the 1920s.<ref name=":0" /> He called these the form constants: Tunnels, Spirals, Honeycombs Gratings, and Cobwebs. These also apply to both drug-induced and natural hallucinations, which appear in near-death experiences, sensory deprivation, waking up or falling asleep, and during migraines.<ref>{{cite journal | vauthors = Bressloff PC, Cowan JD, Golubitsky M, Thomas PJ, Wiener MC | s2cid = 207683037 | title = What geometric visual hallucinations tell us about the visual cortex | journal = Neural Computation | volume = 14 | issue = 3 | pages = 473–91 | date = March 2002 | pmid = 11860679 | doi = 10.1162/089976602317250861 | hdl = 10044/1/107924 | hdl-access = free }}</ref> According to Klüver, all hallucinations consist of shapes in one of these categories and 'atypical' hallucinations are simply variations. The form constants are common in chromesthetic experiences.<ref name=":0" />

Psychedelics greatly enhance suggestibility, so it is fairly common to mistake hallucinations with chromesthesia;<ref name=":3" /> especially considering that all measures of color perception including brightness, saturation, luminance, contrast, and hue are affected due to chemical agents. Drug-induced chromesthesia, as opposed to congenital chromesthesia, is not consistent or automatic. Furthermore, bottom-up processing is responsible for experiences under drug influence, so external stimuli and context are not as critical.<ref name=":0" />

Several studies, both direct (intentionally trying to induce synesthesia) and indirect (participants respond to a set of questions, including one about synesthetic experiences), suggest that the induction of synesthesia with chemical agents is possible. Nevertheless, most studies "suffer from a large number of limitations including a lack of placebo control, double-blinds, and randomized allocation".<ref name=":3" />

Hallucinogen Persisting Perception Disorder occurs when hallucinations continue after the drug has been metabolized by the body.<ref>{{Cite journal |last1=Orsolini |first1=Laura |last2=Papanti |first2=Gabriele Duccio |last3=De Berardis |first3=Domenico |last4=Guirguis |first4=Amira |last5=Corkery |first5=John Martin |last6=Schifano |first6=Fabrizio |date=2017-11-20 |title=The "Endless Trip" among the NPS Users: Psychopathology and Psychopharmacology in the Hallucinogen-Persisting Perception Disorder. A Systematic Review |journal=Frontiers in Psychiatry |language=English |volume=8 |doi=10.3389/fpsyt.2017.00240 |doi-access=free |issn=1664-0640|pmc=5701998 }}</ref><ref>{{Cite web |title=Hallucinogen Persisting Perception Disorder - EyeWiki |url=https://eyewiki.org/Hallucinogen_Persisting_Perception_Disorder |access-date=2025-07-13 |website=eyewiki.org |language=en}}</ref>

== Music and chromesthesia == Individuals with chromesthesia are more likely to play musical instruments and be artistically inclined. Furthermore, "both the hobbies and occupations of synesthetes are skewed toward the creative industries."<ref name=":2" /> People with synesthetic propensities are more metaphorical since the same genes cause them to relate concepts and ideas and, thus, be more creative. This could explain the higher incidence of musicians who have synesthesia.<ref>{{cite book|last1=Robertson|first1=Lynn C. |last2=Sagiv|first2=Noam | name-list-style = vanc |url=https://books.google.com/books?id=Bm92CAAAQBAJ&q=The+proportion+of+synesthetes+among+artists+is+around+twice+as+high+as+it+is+in+the+general+population.&pg=PT214|title=Synesthesia: Perspectives from Cognitive Neuroscience|date=2004-10-14|publisher=Oxford University Press|isbn=978-0-19-029028-3|language=en}}</ref>

However, musical experience does not assist the ability to consistently match colors to tones. Against natural expectation, studies have found that possession of absolute pitch increased local variance in matching ability.<ref name = "Head"/> One possible explanation for this is that because absolute pitch is subject to chance error, occasionally incorrectly inferred note names could compete with the pitch-induced color on particular trials.<ref name = "Head"/> Another possibility is that people with absolute pitch can label tighter pitch recognition categories than normal, introducing a greater number of category boundaries to cross between distinct tones.<ref name = "Head"/>

=== Composers with chromesthesia === Franz Liszt was a composer who was known for asking performers to play with color. He was noted telling his orchestra to play the music in a "Bluer Fashion," <ref name="auto">{{cite web|url=http://www.daysyn.com/Synesthete-composers-and-musicians.html#anchor_96|title=Synesthete-composers-and-musicians|website=www.daysyn.com|access-date=2019-10-15}}</ref> since that is what the tone required. Synesthesia was not a common term in Liszt's time; people thought he was playing a trick on them when he referred to a color instead of a musical term.

Leonard Bernstein openly discussed his chromesthesia, which he described as a "timbre to color."<ref name="auto"/> Although he does not reference specific songs as being a certain color, he does explain the way it should sound to the artist performing. There are recordings of him stopping orchestras and singers when they are changing the "timbre."<ref>{{cite web|url=https://www.youtube.com/watch?v=UoKZlcidbms |archive-url=https://ghostarchive.org/varchive/youtube/20211221/UoKZlcidbms|archive-date=2021-12-21|url-status=live|title=Tenor Keeps Screwing Up while Bernstein Conducts - Awkward Sequence|date=18 November 2014 |via=www.youtube.com}}{{cbignore}}</ref> If someone changes the "timbre" or tone in a piece, it does not necessarily change the sound to the listener, but the composer with Chromesthesia will automatically know.

Amy Beach was another composer who had synesthesia. According to her perspective, each key signature was associated with a particular color. If an artist changed the key to suit their voice, then she would become upset because it would change the intended sound, portrayal, and emotion of the piece.<ref name="auto"/>

Tori Amos has described seeing music as structures of light since early childhood, an experience consistent with chromesthesia.{{sfn|Amos|Powers|2005|p=123}}

Olivier Messiaen was influenced by the color of musical keys for his compositions.<ref name=":2" /> thumb|Alexander Scriabin. It is debatable whether Scriabin had chromesthesia or if his analogies were purely associative

==== Alexander Scriabin ==== {{Main|Alexander Scriabin|Clavier à lumières}} [[File:Colorchart.jpg|thumb|The Theosophist "meanings of colors" of thought-forms and human aura associated with feelings and emotions]] Alexander Scriabin was a Russian composer and pianist. He is famously regarded as a synesthete, but there is a lot of controversy surrounding whether he had chromesthesia or not.<ref name=":6">{{cite journal| vauthors = Galeyev BM, Vanechkina IL |s2cid=57564192|date=2001|title=Was Scriabin a Synesthete?|journal=Leonardo|volume=34|issue=4|pages=357–361|doi=10.1162/00240940152549357|jstor=1577166|issn=0024-094X}}</ref> Scriabin was a major proponent of Theosophy, which had a system associating colors to feelings and emotions.<ref>{{cite journal|last=Altman|first=Michael J. | name-list-style = vanc |date=2017-08-24|title=The Theosophical Quest for Occult Power|journal=Oxford Scholarship Online|doi=10.1093/acprof:oso/9780190654924.003.0005}}</ref> This influenced the musician, who distinguished "spiritual" tonalities (like F-sharp major) from "earthly, material" ones (C major, F major).<ref name=":6" /> Furthermore, Alexander Scriabin developed a "keyboard with lights" or clavier à lumières, which directly matched musical notes with colors.<ref name=":6" />

"Scriabin believed integration of colored light within a symphonic work would act as a 'powerful psychological resonator for the listener'".<ref name=":7">{{cite journal|last=Peacock|first=Kenneth| name-list-style = vanc |date=1985|title=Synesthetic Perception: Alexander Scriabin's Color Hearing|journal=Music Perception|volume=2|issue=4|pages=483–505|doi=10.2307/40285315|jstor=40285315|issn=0730-7829}}</ref> That is why he created the clavier à lumières for his color-symphony ''Prometheus: The Poem of Fire.'' This consisted of a color organ, which projected colors on a screen.<ref name=":7" /> The musicologist Sabaneyev first published a table of Scriabin's sound-to-color mapping in 1911:<ref name=":6" /> {| class="wikitable" |+'''Scriabin's sound-to-color associations''' <ref name=":6" /> !Note !Color |- |C |Red |- |G |Orange-pink |- |D |Yellow |- |A |Green |- |E |Whitish-blue |- |B |Similar to E |- |F♯ |Blue, bright |- |D♭ |Violet |- |A♭ |Purplish-violet |- |E♭ |Steel color with metallic sheen |- |B♭ |Similar to E flat |- |F |Red, dark |} Scriabin was friends with composer Nikolai Rimsky-Korsakov, who was a synesthete, and their sound-to-color associations were not the same. Specifically, Rimsky-Korsakov made a distinction between major and minor scales and his associations had a "more neutral, spontaneous character".<ref name=":6" /> Still, different individuals respond to some sounds and not others, and sound-to-color associations vary greatly between them.<ref name=":0" /> [[File:Scriabin-Circle.svg|thumb|Scriabin's sound-to-color associations arranged into a circle of fifths, demonstrating its spectral quality]] When the notes are ordered by the circle of fifths, the colors are in order of a spectrum, which casts doubt on whether Scriabin experienced chromesthesia:<ref>{{cite book|last=Harrison | first = John E.| name-list-style = vanc |title=Synaesthesia : the strangest thing|date=2001|publisher=Oxford University Press|isbn=0-19-263245-0|location=Oxford|oclc=45446164}}</ref> {| class="wikitable" |+'''Scriabin's sound-to-color circle of fifths''' <ref name=":6" /> !Note !Color |- |C |Red |- |G |Orange |- |D |Yellow |- |A |Green |- |E |Sky blue |- |B |Blue |- |F♯/ G♭ |Bright blue or violet |- |D♭ |Violet or purple |- |A♭ |Violet or lilac |- |E♭ |Flesh or steel |- |B♭ |Rose |- |F |Deep red |} Whether Scriabin had chromesthesia or not, his work was greatly influenced by the particularities of this phenomenon. He created a system that associated colors to tones and aimed to create holistic sensory experiences with his compositions. Not only did he experiment with colors, but also with "the generation of scents and sensation of touch and taste".<ref name="pmid25684291">{{cite book|vauthors=Altenmüller E|chapter=Alexander Scriabin |title=Music, Neurology, and Neuroscience: Historical Connections and Perspectives|series=Progress in Brain Research|volume=216|pages=197–215|date=2015|pmid=25684291|doi=10.1016/bs.pbr.2014.11.031|chapter-url=https://books.google.com/books?id=4xGdBAAAQBAJ&q=value+of+scriabin's+circle+of+fifths&pg=PA198|isbn=978-0-444-63410-8}}</ref>

== See also ==

* Synesthesia

==References== {{reflist|30em}}

===Works cited=== {{refbegin}} * {{cite book|last1=Amos|first1=Tori|last2=Powers|first2=Ann|author-link2=Ann Powers|title=Tori Amos: Piece by Piece|year=2005|publisher=Broadway Books|isbn=978-0-7679-1677-6|url=https://books.google.com/books?id=1LE3VkMtdSkC}} {{refend}}

==External links== *{{Commons category-inline}}

{{Color topics}}

Category:Color Category:Synesthesia