Sørensen, Thomas Alrik

Zelazny, Aurore

English

Does Monday have a specific color? What does the ABC song taste like? These may sound like strange questions, but for a small number of people, such questions may be very reasonable. This is due to a phenomenon called synesthesia. It originates from Greek, meaning “joined” (syn) and “sensations” (esthesia). We experience the environment through a range of senses. You may hear music with your ears or enjoy the color of a clear sky with your eyes. However, when someone has synesthesia, certain experiences seem to have an additional sensory dimension. So, on top of hearing music, a person with synesthesia may also see the song in front of them. The phenomenon is still not fully understood. However, there are several suggestions about its mechanisms. Synesthesia provides an insight into individual differences in how we experience the world we live in

    Aalborg UniversitetSynesthesia - are all Mondays blue?Zelazny, Aurore; Sørensen, Thomas AlrikPublished in:Frontiers for Young MindsDOI (link to publication from Publisher):10.3389/frym.2022.650593Creative Commons LicenseCC BY 4.0Publication date:2022Document VersionPublisher's PDF, also known as Version of recordLink to publication from Aalborg UniversityCitation for published version (APA):Zelazny, A., & Sørensen, T. A. (2022). Synesthesia - are all Mondays blue? Frontiers for Young Minds.https://doi.org/10.3389/frym.2022.650593General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            - Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            - You may not further distribute the material or use it for any profit-making activity or commercial gain            - You may freely distribute the URL identifying the publication in the public portal -Take down policyIf you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access tothe work immediately and investigate your claim.Downloaded from vbn.aau.dk on: November 19, 2022NEUROSCIENCE AND PSYCHOLOGYPublished: 27 May 2022doi: 10.3389/frym.2022.650593SYNESTHESIA—ARE ALL MONDAYS BLUE?Aurore Zelazny 1,2*† and Thomas Alrik Sørensen 1,2†1Centre for Cognitive Neuroscience, Department of Communication and Psychology, Aalborg University, Aalborg, Denmark2Sino-Danish College (SDC), University of Chinese Academy of Sciences, Beijing, ChinaYOUNG REVIEWERS:ASHMITAAGE: 15LICEOSCIENTIFICOM. G.AGNESIAGES: 14–15Does Monday have a specific color? What does the ABC songtaste like? These may sound like strange questions, but for a smallnumber of people, such questions may be very reasonable. This isdue to a phenomenon called synesthesia. It originates from Greek,meaning “joined” (syn) and “sensations” (esthesia). We experience theenvironment through a range of senses. You may hear music withyour ears or enjoy the color of a clear sky with your eyes. However,when someone has synesthesia, certain experiences seem to havean additional sensory dimension. So, on top of hearing music, aperson with synesthesia may also see the song in front of them.The phenomenon is still not fully understood. However, there areseveral suggestions about its mechanisms. Synesthesia provides aninsight into individual di erences in how we experience the worldwe live in.kids.frontiersin.org May 2022 | Volume 10 | Article 650593 | 1Zelazny and Sørensen Synesthesia—Are All Mondays Blue?WHAT IS SYNESTHESIA?When navigating the environment, our senses collect information.Sensory information is then processed by the brain to guide ouractions and behaviors. We tend to assume that whenwe see an object,say an apple, everyone else sees and experiences the apple the sameway. Philosophers have debated whether we can ever be sure aboutother people’s experiences. Examples continually emerge indicatingthat people have di erent ways of experiencing theworld. SynesthesiaSYNESTHESIAA brain phenomenon inwhich a stimulustriggers a typicalsensation, such asseeing the letter “A,”followed by anunrelated sensation,like seeing thecolor yellow.is one such example, demonstrating that sensory experiences can varybetween observers. Synesthesia is derived from the Greek words “syn,”meaning “joined,” and “esthesia,” meaning “sensations.” Synesthesiais estimated to occur in about 4% of the population. Synesthesiacan vary between people because there are many di erent typesof synesthesia. One estimate is that there are at least 70 di erentvariations1. Some people experience colors when they see letters [1].1 http://www.daysyn.com/Types-of-Syn.htmlFor others, weekdays have a specific color, for example Monday is redand Tuesday is yellow. There are also people who taste words.In the example in which Monday is red, we call Monday the inducer,INDUCERThe piece ofinformation that causesa synesthesiaexperience, such as aletter, a number ora song.because it causes the synesthesia experience. We call red theconcurrent, because it is the sensory experience that follows fromCONCURRENTThe unrelatedsensation that comesas a reaction to certainstimuli, as such thecolor sensation thatfollows seeing a letter.thinking about Monday. A person who experiences synesthesia iscommonly called a synesthete. A synesthete may have several typesSYNESTHETEA person whoexperiences synesthesia.of synesthesia in varying degrees. In other words, there is a wide rangeof di erent experiences a synesthete may have.If there is that much variation, how are we sure that all the examplesare synesthesia? Not all synesthetes would associate the number 4with the same color, for example. Nevertheless, all types of synesthesiashare some common features. One is that the associations seem stableover time. Imagine a person for whom the letter A is a particular hueof red. That person will report the same red hue when asked about iteven weeks apart.Figure 1 shows drawings from Anneline, who is a synesthete. Shemade a drawing of her synesthesia for numbers and shapes back in2013 (Figure 1A). Seven years later, we asked her to redraw how sheexperiences numbers and shapes (Figure 1B). Anneline has severalforms of synesthesia, and among these, she experiences colors fornumbers and shapes. Numbers are also associated with various sizes.Interestingly, this size di erence does not correspond to the numericquantity. Shewould describe the number six as very annoying due to itssmall size,making it very dicult to see. However, she likes the numberfive because it is large, orange, and easy to see.In addition to synesthetes’ direct descriptions of their synesthesia, it ispossible to demonstrate in the lab that these associations influenceperception. Synesthetes process letters faster when the letters areshown in their synesthetic color. Synesthetes also have to use fewerkids.frontiersin.org May 2022 | Volume 10 | Article 650593 | 2Zelazny and Sørensen Synesthesia—Are All Mondays Blue?Figure 1Figure 1Synesthesia fornumbers and shapes.(A) A drawing fromAnneline in 2013, withthe title “the correctcolors—numbers andgeometrical shapes.”Her drawing shows thecolors and sizes eachnumber has for her. (B)Another drawing byAnneline in 2020. Sevenyears later, her colorsand sizes have notchanged. (C) Drawingby Aurore in 2020. Shehas di erent colorprofiles for numbersand shapes. A fewcolors are similar toAnneline’s (1, 2, 3, forexample), while others(4, 5, square) are verydi erent.memory resources than they do if the letters are shown in a di erentcolor [1].Four di erent explanations for synesthesia have been suggested.The cross-activation theory, the disinhibited feedback theory, theFEEDBACKA process ofinformation travelingfrom the associativearea back to thesensory area.re-entrant hypothesis, and the developmental learning hypothesis.TOOMANY CONNECTIONS IN THE BRAINTo understand the first explanation, we can think about the brain asa house. We first need to build the house. This happens before weare born and for the first couple of years of our lives. We say that thebrain is maturating. But this is a strange house in the beginning. Thebuilder is not sure how we will want to use various rooms. Therefore,he connects every electrical switch to several di erent outlets. Whatdoes it mean for the brain? It means that there are way too manyconnections between brain cells (called neurons) and between variousareas of the brain. When people move into the house, they decidewhere to plug in the lamps, the TV, the toaster, etc. They call in anelectrician and ask him to remove all the cables that connect switchesto the wrong outlets. Now, when the people want to turn on thekettle, they know which switch to use—that switch now turns on thekettle only.A similar process happens in the brain when children are about 2years old. A child’s experiences of the world will decide which brainconnections are useful. The useless ones will disappear while theuseful ones will become stronger. We call this process pruning. InPRUNINGA brain process inwhich connectionsbetween neurons thatare not used areremoved. At the sametime, usefulconnectionsare strengthened.kids.frontiersin.org May 2022 | Volume 10 | Article 650593 | 3Zelazny and Sørensen Synesthesia—Are All Mondays Blue?the case of synesthesia, the cross-activation theory [2] suggests thatthe electrician forgot one of the useless connections. Now, whenpeople turn on their living room light, it also turns on the TV! Inother words, some brain connections that were supposed to disappearhave remained (Figure 2A). When the synesthete hears music, theinformation goes to their auditory (hearing) system, as expected.However, it also activates parts of the visual system. So, that personmay see shapes or colors every time they listen to a song.Figure 2Figure 2(A) The cross-activationtheory states that, insynesthesia, someuseless brainconnections are notpruned as they are innon-synesthetes,keeping unrelated brainareas connected (greenlines). (B) Thedisinhibited feedbacktheory states that, insynesthetes,information travelsback (green arrow) toparts of the brain. Innon-synesthetes, thisfeedback is inhibited.(C) The re-entranthypothesis states that,when seeing a letter asynesthete recognizes,a feedback process(green arrow) willoccur, but when seeinga letter she does notrecognize, no feedbackwill be initiated.OOPS, WRONGWAY!According to the second explanation, synesthesia is not due todi erences in the structure of the brain. Instead, this explanationhypothesizes that synesthesia comes from di erences in the waypeople process sensory information. Let us take the example ofsomeone reading the letter A. Information first enters through theperson’s eyes, then it arrives at the visual area, at the back of thebrain. This is called a sensory area. Here, the information is analyzedSENSORY AREABrain areas that processinformation from oursenses—sight, hearing,touch, etc.in several steps. We can imagine it as an assembly line, in which eachworker evaluates a specific aspect of the information, spottingwhetherit contains a straight line, if the image is moving, or if it is colored, forexample. Once the image has been analyzed, the information moveson to be processed in the associative areas of the brain. There, theASSOCIATIVE AREASBrain areas in whichinformation from thevarious senses iscombined. Morecomplex processesoccur, such asunderstanding andreacting to whatwe read.information from various sources is combined. Naming the letter, orlisting words that start with A, are examples of associative tasks. Oncethe information has been processed by the associative areas, it travelsback to the sensory area. This process is called feedback. However,since the information has already been treated there, it does not getpassed on further—we say that it is inhibited. The disinhibited feedbacktheory [3] suggests that, in synesthetes, the inhibition process may notoccur correctly (Figure 2B). Instead, the information gets analyzed inthe sensory area one more time. Take the case of Anneline. Every timekids.frontiersin.org May 2022 | Volume 10 | Article 650593 | 4Zelazny and Sørensen Synesthesia—Are All Mondays Blue?an A is sent back to the visual sensory area, is it also labeled with theadditional sensation of yellow.The re-entrant hypothesis [4] is a variation of this idea (Figure 2C). Inthe disinhibited feedback theory, visual information is spontaneouslysent back from the associative area to the sensory area. However,according to the re-entrant hypothesis, this feedback process is notspontaneous—it can happen only if themeaning of the letter is known.Take Anneline, who can read English and Danish. Now imagine weshow her the Japanese grapheme?, which is equivalent to A. She willnot get any colored response to it, as her brain does not know whatit means. Aurore however can read Japanese. When she sees?, sheexperiences pink (Figure 1C).A LEARNING TRICK OF THEMINDThe three hypotheses presented so far try to explain how the brain ofa person with synesthesia functions. They do not try to explain whyonly some people have synesthesia. You may have noticed that theinducers, like letters or months, are concepts that we do not knowfrom birth. We learn about these concepts as we grow up, and theyare not the same in every culture. For example, not all languagesare written with the same symbols. This led researchers to wonderwhether synesthesia is involved in the learning process. Learning everyletter and being able to use them all is a dicult task for somepeople. So, it is possible that their brains came up with a trick. Theirbrains slowly started to associate the concept of the letter A to aspecific color, to help them tell the di erence between letters. A similarprocess may occur for all types of synesthesia inducers. Researcherscall this explanation the developmental learning hypothesis [5].SUMMARYSynesthesia gives people a particular experience of the world. Theorigin of synesthesia is still a mystery to researchers. However, greatprogress has been made, and we now know more about the di erentprofiles of synesthetes. We also have some hypotheses regardingthe brain mechanisms involved. Understanding synesthesia can helpus understand the individual di erences in how our brain processesinformation. It could help us discovering new ways to overcomelearning diculties.ACKNOWLEDGMENTSThe authors would like to thank the Independent Research FundDenmark for funding the project Synaesthesia – the Roles ofAssociation Learning and of Di erential Brain Development. Also,thanks to Pauline Cantou for comments on earlier versions ofthe manuscript.kids.frontiersin.org May 2022 | Volume 10 | Article 650593 | 5Zelazny and Sørensen Synesthesia—Are All Mondays Blue?REFERENCES1. Ásgeirsson, Á. G., Nordfang, M., and Sørensen, T. A. 2015. Components ofattention in grapheme-color synesthesia: a modeling approach. PLoS ONE10:e0134456. doi: 10.1371/journal.pone.01344562. Ramachandran, V. S., and Hubbard, E. M. 2001. Synaesthesia–a window intoperception, thought and language. J. Conscious. Stud. 8:3–34.3. Grossenbacher, P. G., and Lovelace, C. T. 2001. Mechanisms of synesthesia:cognitive and physiological constraints. Trends Cogn. Sci.5:36–41. doi: 10.1016/S1364-6613(00)01571-04. Smilek, D., Dixon, M. J., Cudahy, C., and Merikle, P. M. 2001. Synaestheticphotisms influence visual perception. J. Cogn. Neurosci.13:930–6. doi: 10.1162/0898929017531658455. Watson, M. R., Chromý, J., Crawford, L., Eagleman, D. M., Enns, J. T., and Akins,K. A. 2017. The prevalence of synaesthesia depends on early language learning.Conscious. Cogn., 48:212–31. doi: 10.1016/j.concog.2016.12.004SUBMITTED: 07 January 2021; ACCEPTED: 02 May 2022;PUBLISHED ONLINE: 27 May 2022.EDITOR: Robert J. Zatorre, McGill University, CanadaSCIENCE MENTORS: Alina Quach and Elena BrivioCITATION: Zelazny A and Sørensen TA (2022) Synesthesia—Are All Mondays Blue?Front. Young Minds 10:650593. doi: 10.3389/frym.2022.650593CONFLICT OF INTEREST: The authors declare that the research was conducted inthe absence of any commercial or financial relationships that could be construedas a potential conflict of interest.COPYRIGHT © 2022 Zelazny and Sørensen. This is an open-access articledistributed under the terms of the Creative Commons Attribution License (CC BY).The use, distribution or reproduction in other forums is permitted, provided theoriginal author(s) and the copyright owner(s) are credited and that the originalpublication in this journal is cited, in accordance with accepted academic practice.No use, distribution or reproduction is permitted which does not comply with theseterms.YOUNG REVIEWERSASHMITA, AGE: 15A highschool student greatly driven by her fiery passion and love for learning. Herinterests include:∼Psychology∼Neurosciencekids.frontiersin.org May 2022 | Volume 10 | Article 650593 | 6Zelazny and Sørensen Synesthesia—Are All Mondays Blue?∼Education∼Health & Wellness∼Kinesiology∼Leadership∼Social Justice∼DanceApart from school, she spends much of her time working for and runningorganizations. She is a mental health and social justice advocate and devotes manyhours raising awareness on issues important to her, especially by participating inmedia-based organizations. In her free time, she enjoys reading books , listening tomusic , binging TV shows , hanging out with friends , dancing , and exploringnew things . She is also a BTS ARMY .LICEO SCIENTIFICO M. G. AGNESI, AGES: 14–15Hi, we are the class 1AS from the Liceo Scientifico M.G. Agnesi, in Italy. We think thiswas a really good project and could be quite useful to some of us in the future. Wefound it very interesting because we learned things we did not know before: it gaveus a chance to expand our curiosity and our knowledge.AUTHORSAURORE ZELAZNYI have always been fascinated by languages and the brain. I started o  studyinglinguistics, then I became interested in how language works in the brain. As asynesthete myself, I wondered whether synesthesia is related to early languagelearning. I am interested in how synesthesia is involved in acquiring expert knowledgeof new concepts. I work at the Center for Cognitive Neuroscience at AalborgUniversity in Denmark. *aurore@hum.aau.dkTHOMAS ALRIK SØRENSENI have a keen interest in memory and perception and how expertise influencesperceptual processes. During my Ph.D. at the University of Copenhagen Istarted to investigate how short-term memory was influenced by various factors,which has since led to a more general interest in what shapes the way weexperience our environments. Synesthesia is a particularly interesting phenomenon,as synesthetes clearly demonstrate a di erence in perceptual content compared tonon-synesthetes, which may help us to better understand what drives individualdi erences in perception. I am heading the Center for Cognitive Neuroscience atAalborg University.†These authors have contributed equally to this work and share first authorshipkids.frontiersin.org May 2022 | Volume 10 | Article 650593 | 7

Synesthesia - are all Mondays blue?

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