Table of ContentsView AllTable of ContentsWhat Does It Feel Like?Who Gets It?CausesOther Types & SymptomsTestingTreatmentsOutlook
Table of ContentsView All
View All
Table of Contents
What Does It Feel Like?
Who Gets It?
Causes
Other Types & Symptoms
Testing
Treatments
Outlook
Synesthesia is a neurological phenomenon in which information meant to stimulate one sense stimulates additional senses, as well. For example, someone with synesthesia may “see” music, “hear” colors, “taste” textures, “smell” movement, and so on.Approximately 4% of the general population has some form of synesthesia.
This article covers the different types of synesthesia.
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What Is Synesthesia Like?
Synesthesia is essentially the merging of multiple senses. It is not a disorder, but rather a way of perceiving the world.
Not everyone experiences synesthesia the same way since synesthesia depends on which senses are paired. Some examples of how synesthesia might feel include:
Most Common Forms of SynesthesiaOne of the most common forms of synesthesia is “colored hearing,” or seeing colors when you hear certain music, sounds, or voices.Another common form is seeing colors associated with numbers or letters. It is estimated about 1% of the general population has this type of synesthesia.
Most Common Forms of Synesthesia
One of the most common forms of synesthesia is “colored hearing,” or seeing colors when you hear certain music, sounds, or voices.Another common form is seeing colors associated with numbers or letters. It is estimated about 1% of the general population has this type of synesthesia.
For the most part, people report that these sensations are experienced internally, in their mind. A rare group of people may see colors or images projected in their vision, typically a few feet away from their body.
Who Gets Synesthesia?
Synesthesia has been described as a neurodevelopmental condition. Synesthesia can be:
Synesthesia is also associated with higher rates of certain mental health conditions and traits. This includes:
Is Synesthesia a Form of Autism?
No, synesthesia is not a form of autism. However, synesthesia is about 3 times more common among people with autism than it is in the general population.
A 2023 twin study found that there is a genetic link between autism and synesthesia.
What Causes Synesthesia?
Scientists do not agree on the exact cause of synesthesia.
Theories on what causes synesthesia include:
Hyperconnectivity
In adulthood, those with synesthesia have hyperconnectivity of neurons in the sensory areas of the brain. This could explain why auditory input meant to stimulate the sound perception area of the brain, may also pass through the visual perception area of the brain and lead to sound-color synesthesia.
Feed-Backward Connections
An alternate theory is that people with synesthesia have normal brain “architecture,” or in other words, a normal amount of neurons, but these neurons operate in an unusual way. There is a lack of inhibition, leading to the neurons firing backward into overlapping sensory areas of the brain, leading to synesthetic experiences.
Genetic
Many scientists agree that there is a genetic component to synesthesia.Synesthesia commonly occurs in families, and twin studies have even found genetic links between synesthesia and conditions like autism and schizophrenia.A single “synesthesia gene” has not yet been identified.
Learning
Associating two senses together can be useful in early childhood for learning numbers, letters, words, music, and more. Some researchers argue that synesthesia is, in part, a learned skill leftover from childhood.
Other Synesthesia Types and Symptoms
Synesthesia symptoms vary based on the type, and a person can have more than one type.
Types of synesthesia include:
This is not a complete list of all types of synesthesia. There are countless forms of synesthesia, typically described as the sensory inducer, such as sound, to the sensation, such as smell.
It is possible for someone to have more than one type of synesthesia at once.For example, someone with both grapheme-color and ordinal-linguistic synesthesia might experience the number four as both yellow and male.
Synesthesia Testing
It is challenging to test synesthesia because each person’s experience is very individual. The Synesthesia Battery is one validated test for grapheme-color synesthesia.
Tests for synesthesia, including the Synesthesia Battery, can be taken online.
Consistency Test for Synesthesia
The consistency test looks for grapheme-color synesthesia. During this type of test, you are given stimuli (such as numbers or letters) and asked to share your synesthetic experience (such as an associated color). This test is done multiple times over weeks, months, or years.
A test positive for synesthesia would have consistent answers over time. For example, if a synesthetic person said the number eight is green, they would still experience it as green a year or more later. Synesthetes are consistent about 90% of the time, whereas non-synesthetes are consistent only about 20% of the time.
How Is Synesthesia Treated?
Synesthesia is not a mental illness. Treatment for synesthesia does not yet exist. In fact, many people with synesthesia view this condition as a gift, a special power, or an extra sense.
However, some people with synesthesia experience sensory overload, which can make it challenging to go in public or exist in loud, colorful, or busy places.Talk to your healthcare provider if sensory overload from synesthesia is impacting your functioning.
Long-Term Outlook for People With Synesthesia
Most people with synesthesia are able to live a normal life. In fact, for many people synesthesia is “normal” to them, and when they realize that not everyone else experiences the world the same way, this can sometimes be viewed as something that makes them special and unique.
Research also tells us that people with synesthesia have advantages in memory and creativity.Many people with synesthesia have success in creative professions as poets, artists, musicians, and more.
Summary
Synesthesia is the merging of senses. Information meant to trigger one sense may actually trigger several, for example seeing the number eight as green, tasting the word “generous” as chocolate pudding, or seeing music as fireworks. There are many types of synesthesia.
17 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.American Psychological Association.Everyday fantasia: The world of synesthesia.Van Leeuwen TM, Neufeld J, Hughes J, Ward J.Synaesthesia and autism: Different developmental outcomes from overlapping mechanisms?Cognitive Neuropsychology. 2020;37(7-8):433-449. doi: 10.1080/02643294.2020.1808455Ward J, Simner J.Synesthesia: The current state of the field.Multisensory Perception. Published online January 1, 2020:283-300. doi: 10.1016/B978-0-12-812492-5.00013-9Baron-Cohen S, Johnson D, Asher J, et al.Is synaesthesia more common in autism?Molecular Autism. 2013;4(1):40. doi: 10.1186/2040-2392-4-40van Leeuwen T, Wilsson L, Norrman H, Dingemanse M, Bolte S, Neufeld J.Perceptual processing links autism and synesthesia: A co-twin control study.Cortex. 2021;145:236-249. doi: 10.1016/j.cortex.2021.09.016Meier B.Synesthesia. In:Encyclopedia of Behavioral Neuroscience, 2nd Edition. Elsevier; 2022:561-569. doi: 10.1016/B978-0-12-819641-0.00134-1Taylor MJ, van Leeuwen TM, Kuja-Halkola R, et al.Genetic and environmental architecture of synaesthesia and its association with the autism spectrum—a twin study.Proc R Soc B. 2023;290(2009):20231888. doi: 10.1098/rspb.2023.1888National Autistic Society.Synaesthesia in autism.Maurer D, Ghloum JK, Gibson LC, et al.Reduced perceptual narrowing in synesthesia.Proc Natl Acad Sci USA. 2020;117(18):10089-10096. doi: 10.1073/pnas.1914668117Watson MR, Akins K, Spiker C, Crawford L, Enns JT.Synesthesia and learning: a critical review and novel theory.Front Hum Neurosci. 2014;8:72811. doi: 10.3389/fnhum.2014.00098Ward J, Simner J.How do different types of synesthesia cluster together? Implications for causal mechanisms.Perception. 2022;51(2):91-113. doi: 10.1177/03010066211070761Lungu L, Rothen N, Terhune D.The time course of synaesthetic colour perception.Cortex. 2021;141:322-330. doi: 10.1016/j.cortex.2021.04.018Chun CA, Hupé JM.Mirror-touch and ticker tape experiences in synesthesia.Front Psychol. 2013;4:61894. doi: 10.3389/fpsyg.2013.00776Gertner L, Henik A, Reznik D, Cohen Kadosh R.Implications of number-space synesthesia on the automaticity of numerical processing.Cortex. 2013;49(5):1352-1362. doi: 10.1016%2Fj.cortex.2012.03.019Edelstein M, Brang D, Rouw R, Ramachandran VS.Misophonia: physiological investigations and case descriptions.Front Hum Neurosci. 2013;7:296. doi: 10.3389%2Ffnhum.2013.00296Carmichael DA, Down MP, Shillcock RC, Eagleman DM, Simner J.Validating a standardised test battery for synesthesia: Does the Synesthesia Battery reliably detect synesthesia?Consciousness and Cognition. 2015;33:375-385. doi: 10.1016/j.concog.2015.02.001Lunke K, Meier B.Creativity and involvement in art in different types of synaesthesia.Br J Psychol. 2019;110(4):727-744. doi: 10.1111%2Fbjop.12363
17 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.American Psychological Association.Everyday fantasia: The world of synesthesia.Van Leeuwen TM, Neufeld J, Hughes J, Ward J.Synaesthesia and autism: Different developmental outcomes from overlapping mechanisms?Cognitive Neuropsychology. 2020;37(7-8):433-449. doi: 10.1080/02643294.2020.1808455Ward J, Simner J.Synesthesia: The current state of the field.Multisensory Perception. Published online January 1, 2020:283-300. doi: 10.1016/B978-0-12-812492-5.00013-9Baron-Cohen S, Johnson D, Asher J, et al.Is synaesthesia more common in autism?Molecular Autism. 2013;4(1):40. doi: 10.1186/2040-2392-4-40van Leeuwen T, Wilsson L, Norrman H, Dingemanse M, Bolte S, Neufeld J.Perceptual processing links autism and synesthesia: A co-twin control study.Cortex. 2021;145:236-249. doi: 10.1016/j.cortex.2021.09.016Meier B.Synesthesia. In:Encyclopedia of Behavioral Neuroscience, 2nd Edition. Elsevier; 2022:561-569. doi: 10.1016/B978-0-12-819641-0.00134-1Taylor MJ, van Leeuwen TM, Kuja-Halkola R, et al.Genetic and environmental architecture of synaesthesia and its association with the autism spectrum—a twin study.Proc R Soc B. 2023;290(2009):20231888. doi: 10.1098/rspb.2023.1888National Autistic Society.Synaesthesia in autism.Maurer D, Ghloum JK, Gibson LC, et al.Reduced perceptual narrowing in synesthesia.Proc Natl Acad Sci USA. 2020;117(18):10089-10096. doi: 10.1073/pnas.1914668117Watson MR, Akins K, Spiker C, Crawford L, Enns JT.Synesthesia and learning: a critical review and novel theory.Front Hum Neurosci. 2014;8:72811. doi: 10.3389/fnhum.2014.00098Ward J, Simner J.How do different types of synesthesia cluster together? Implications for causal mechanisms.Perception. 2022;51(2):91-113. doi: 10.1177/03010066211070761Lungu L, Rothen N, Terhune D.The time course of synaesthetic colour perception.Cortex. 2021;141:322-330. doi: 10.1016/j.cortex.2021.04.018Chun CA, Hupé JM.Mirror-touch and ticker tape experiences in synesthesia.Front Psychol. 2013;4:61894. doi: 10.3389/fpsyg.2013.00776Gertner L, Henik A, Reznik D, Cohen Kadosh R.Implications of number-space synesthesia on the automaticity of numerical processing.Cortex. 2013;49(5):1352-1362. doi: 10.1016%2Fj.cortex.2012.03.019Edelstein M, Brang D, Rouw R, Ramachandran VS.Misophonia: physiological investigations and case descriptions.Front Hum Neurosci. 2013;7:296. doi: 10.3389%2Ffnhum.2013.00296Carmichael DA, Down MP, Shillcock RC, Eagleman DM, Simner J.Validating a standardised test battery for synesthesia: Does the Synesthesia Battery reliably detect synesthesia?Consciousness and Cognition. 2015;33:375-385. doi: 10.1016/j.concog.2015.02.001Lunke K, Meier B.Creativity and involvement in art in different types of synaesthesia.Br J Psychol. 2019;110(4):727-744. doi: 10.1111%2Fbjop.12363
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
American Psychological Association.Everyday fantasia: The world of synesthesia.Van Leeuwen TM, Neufeld J, Hughes J, Ward J.Synaesthesia and autism: Different developmental outcomes from overlapping mechanisms?Cognitive Neuropsychology. 2020;37(7-8):433-449. doi: 10.1080/02643294.2020.1808455Ward J, Simner J.Synesthesia: The current state of the field.Multisensory Perception. Published online January 1, 2020:283-300. doi: 10.1016/B978-0-12-812492-5.00013-9Baron-Cohen S, Johnson D, Asher J, et al.Is synaesthesia more common in autism?Molecular Autism. 2013;4(1):40. doi: 10.1186/2040-2392-4-40van Leeuwen T, Wilsson L, Norrman H, Dingemanse M, Bolte S, Neufeld J.Perceptual processing links autism and synesthesia: A co-twin control study.Cortex. 2021;145:236-249. doi: 10.1016/j.cortex.2021.09.016Meier B.Synesthesia. In:Encyclopedia of Behavioral Neuroscience, 2nd Edition. Elsevier; 2022:561-569. doi: 10.1016/B978-0-12-819641-0.00134-1Taylor MJ, van Leeuwen TM, Kuja-Halkola R, et al.Genetic and environmental architecture of synaesthesia and its association with the autism spectrum—a twin study.Proc R Soc B. 2023;290(2009):20231888. doi: 10.1098/rspb.2023.1888National Autistic Society.Synaesthesia in autism.Maurer D, Ghloum JK, Gibson LC, et al.Reduced perceptual narrowing in synesthesia.Proc Natl Acad Sci USA. 2020;117(18):10089-10096. doi: 10.1073/pnas.1914668117Watson MR, Akins K, Spiker C, Crawford L, Enns JT.Synesthesia and learning: a critical review and novel theory.Front Hum Neurosci. 2014;8:72811. doi: 10.3389/fnhum.2014.00098Ward J, Simner J.How do different types of synesthesia cluster together? Implications for causal mechanisms.Perception. 2022;51(2):91-113. doi: 10.1177/03010066211070761Lungu L, Rothen N, Terhune D.The time course of synaesthetic colour perception.Cortex. 2021;141:322-330. doi: 10.1016/j.cortex.2021.04.018Chun CA, Hupé JM.Mirror-touch and ticker tape experiences in synesthesia.Front Psychol. 2013;4:61894. doi: 10.3389/fpsyg.2013.00776Gertner L, Henik A, Reznik D, Cohen Kadosh R.Implications of number-space synesthesia on the automaticity of numerical processing.Cortex. 2013;49(5):1352-1362. doi: 10.1016%2Fj.cortex.2012.03.019Edelstein M, Brang D, Rouw R, Ramachandran VS.Misophonia: physiological investigations and case descriptions.Front Hum Neurosci. 2013;7:296. doi: 10.3389%2Ffnhum.2013.00296Carmichael DA, Down MP, Shillcock RC, Eagleman DM, Simner J.Validating a standardised test battery for synesthesia: Does the Synesthesia Battery reliably detect synesthesia?Consciousness and Cognition. 2015;33:375-385. doi: 10.1016/j.concog.2015.02.001Lunke K, Meier B.Creativity and involvement in art in different types of synaesthesia.Br J Psychol. 2019;110(4):727-744. doi: 10.1111%2Fbjop.12363
American Psychological Association.Everyday fantasia: The world of synesthesia.
Van Leeuwen TM, Neufeld J, Hughes J, Ward J.Synaesthesia and autism: Different developmental outcomes from overlapping mechanisms?Cognitive Neuropsychology. 2020;37(7-8):433-449. doi: 10.1080/02643294.2020.1808455
Ward J, Simner J.Synesthesia: The current state of the field.Multisensory Perception. Published online January 1, 2020:283-300. doi: 10.1016/B978-0-12-812492-5.00013-9
Baron-Cohen S, Johnson D, Asher J, et al.Is synaesthesia more common in autism?Molecular Autism. 2013;4(1):40. doi: 10.1186/2040-2392-4-40
van Leeuwen T, Wilsson L, Norrman H, Dingemanse M, Bolte S, Neufeld J.Perceptual processing links autism and synesthesia: A co-twin control study.Cortex. 2021;145:236-249. doi: 10.1016/j.cortex.2021.09.016
Meier B.Synesthesia. In:Encyclopedia of Behavioral Neuroscience, 2nd Edition. Elsevier; 2022:561-569. doi: 10.1016/B978-0-12-819641-0.00134-1
Taylor MJ, van Leeuwen TM, Kuja-Halkola R, et al.Genetic and environmental architecture of synaesthesia and its association with the autism spectrum—a twin study.Proc R Soc B. 2023;290(2009):20231888. doi: 10.1098/rspb.2023.1888
National Autistic Society.Synaesthesia in autism.
Maurer D, Ghloum JK, Gibson LC, et al.Reduced perceptual narrowing in synesthesia.Proc Natl Acad Sci USA. 2020;117(18):10089-10096. doi: 10.1073/pnas.1914668117
Watson MR, Akins K, Spiker C, Crawford L, Enns JT.Synesthesia and learning: a critical review and novel theory.Front Hum Neurosci. 2014;8:72811. doi: 10.3389/fnhum.2014.00098
Ward J, Simner J.How do different types of synesthesia cluster together? Implications for causal mechanisms.Perception. 2022;51(2):91-113. doi: 10.1177/03010066211070761
Lungu L, Rothen N, Terhune D.The time course of synaesthetic colour perception.Cortex. 2021;141:322-330. doi: 10.1016/j.cortex.2021.04.018
Chun CA, Hupé JM.Mirror-touch and ticker tape experiences in synesthesia.Front Psychol. 2013;4:61894. doi: 10.3389/fpsyg.2013.00776
Gertner L, Henik A, Reznik D, Cohen Kadosh R.Implications of number-space synesthesia on the automaticity of numerical processing.Cortex. 2013;49(5):1352-1362. doi: 10.1016%2Fj.cortex.2012.03.019
Edelstein M, Brang D, Rouw R, Ramachandran VS.Misophonia: physiological investigations and case descriptions.Front Hum Neurosci. 2013;7:296. doi: 10.3389%2Ffnhum.2013.00296
Carmichael DA, Down MP, Shillcock RC, Eagleman DM, Simner J.Validating a standardised test battery for synesthesia: Does the Synesthesia Battery reliably detect synesthesia?Consciousness and Cognition. 2015;33:375-385. doi: 10.1016/j.concog.2015.02.001
Lunke K, Meier B.Creativity and involvement in art in different types of synaesthesia.Br J Psychol. 2019;110(4):727-744. doi: 10.1111%2Fbjop.12363
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