What is Synesthesia? A Clinical Psychology Podcast Episode.
For the past few years in the psychology news section of The Psychology World Podcast, I’ve been covering various news items on Synesthesia. There have been great developments in the research on this condition, but it is still relatively unknown amongst psychologists. Therefore, in this clinical psychology podcast episode, you’ll learn what synesthesia is, what are the causes and a whole lot more. If you’re interested in learning about the condition, perception and cognitive psychology, then this will be a great episode for you.
Today’s psychology podcast episode has been sponsored by Cognitive Psychology: A Guide to Neuropsychology, Neuroscience and Cognitive Psychology. Available from all major eBook retailers and you can order the paperback and hardback copies from Amazon, your local bookstore and local library, if you request it. Also available as an AI-narrated audiobook from selected audiobook platforms and library systems. For example, Kobo, Spotify, Barnes and Noble, Google Play, Overdrive, Baker and Taylor and Bibliotheca.
What is Synesthesia?
Recorded in the 19th century by scientist Francis Galton, even though research wouldn’t really begin into the condition until the 20th century, Synesthesia is a neurological condition where the stimulation of one sensory or cognitive pathway would lead to an involuntary and automatic experience in a second cognitive or sensory pathway. For example, someone might hear a certain sound and see a particular colour.
Another way of putting it is when one sense is activated, another unrelated sense is also activated at the same time. Some people with Synesthesia describe seeing colours when they hear certain sounds and vice versa.
Interestingly, the term given to someone with a lifelong history of Synesthesia can be a “synesthete”, and often these people consider Synesthesia to be a gift. Since the condition allows them to see the world in a very unique way through the integration of multiple senses. As well as it’s important to note that for a person to be a synesthete, consistency is important. Therefore, they need to repeatedly associate the same colour with a sight or sound.
Personally, I really like this idea of a neurological condition being a gift, or at least not being termed negatively or a disadvantage. Of course, there are some people with Synesthesia that think the condition is a curse or it is something that shouldn’t be celebrated or even liked. Yet as a neurodivergent person, I see autism, dyslexia and dyspraxia in the same way. I see them as useful, helpful and I flat out love being autistic because it is seriously helpful in my life. It’s nice to see other neurological conditions are being acknowledged for the benefits that they give people.
Building upon this, Synesthesia is not a mental health condition. Instead it is a neurological condition that is classed as a fresh way of experiencing the world through the mixing of senses that is very unique to the individual. As well as there are benefits of Synesthesia. For instance, research shows that people with Synesthesia have more vivid mental imagery than people without the condition, and some researchers say that this is associated with greater connectivity in the brain. Also, people with the condition demonstrate more creative thinking compared to those without Synesthesia.
Again, it is great that we’ve reached a point where we’re admitting to ourselves that not all differences, especially neurological conditions, are automatically bad, evil or mad things that need to be destroyed. There are a lot of benefits and beauty in being different.
Furthermore, the prevalence rate for Synesthesia is approximately 3% to 5% of the population and women are more likely to have Synesthesia than men.
What Causes Synesthesia?
Whilst the exact causes of Synesthesia are not fully understood, the condition does run in families because Synesthesia can be passed down from parent to child. As well as the condition often appears in early childhood, and there is some debate over whether everyone is born with Synesthesia to some degree, or whether Synesthesia is a special perception of the world that only some people share.
On the other hand, whilst it is rare, it is possible to develop Synesthesia later in life, because of brain tumours, strokes or head trauma. If these are causes of the condition then they are permanent, but the condition can be temporary if caused by meditation, sensory deprivation or the use of psychedelic drugs.
What Are the Different Types of Synesthesia?
With the cause of Synesthesia being unclear, this is important for a few reasons. For instance, the unclear cause of Synesthesia makes it difficult to study or document the wide range of subtypes of the condition. Due to Synesthesia can involve any combination of our senses meaning there might be as many as 60 or 80 subtypes, but not all of these have been documented. As well as a lot of people with Synesthesia have more than one type of the condition.
Some people with Synesthesia perceive texture in response to sight, other people associate shapes with flavours as well as some people hear sounds in response to aromas. These causes amongst others have been documented and studied over the decades so we’ve been able to identify the eight most well-known forms of Synesthesia.
Firstly, there’s lexical-gustatory Synesthesia and this happens when the hearing of certain words triggers distinct tastes within a person.
Secondly, the most common is grapheme-colour Synesthesia when letters and numbers are associated with specific colours. This is a form of the condition that I tend to cover on The Psychology World Podcast when it’s relevant.
Thirdly, auditory-tactile Synesthesia is when a sound triggers a specific bodily sensation, like tingling.
Fourthly, the number form subtype occurs when a person experiences a mental map of numbers that involuntarily appears whenever someone thinks of numbers.
In addition, spatial sequence Synesthesia is when you see numerical sequences or numbers as points in space. For example, you might see the number close up or far away.
Furthermore, ordinal linguistic personification is a subtype of the condition where ordered sequences, like days of the week, are associated with gender or personalities. Now, this is interesting and because I love learning different languages, something I would be interested in knowing (and I doubt the sample size across cultures would be large enough to do a proper empirical comparison) if individuals whose native language is split into different genders, whether or not this subtype is more common. For example, English words don’t have genders, but French, Spanish and Italian do.
Another type of Synesthesia is the mirror-touch subtype. In this type, people describe it as a sort of “supercharged” empathy because a person feels like they’re being touched if they see someone else being touched in the same way. Different people describe the experience differently, because it can be benign as it can be an observed advantage in recognising facial expressions. Equally, this subtype can be a burden because a neurologist with the condition reported intense pressure on their chest when he saw a client receive CPR.
Finally, you have chromesthesia where certain sounds trigger someone to see colours. Such as, you might hear a bicycle bell and see the colour orange. This form of Synesthesia is fairly widespread.
How Does a Person Know If They Have Synesthesia?
I think this is possibly one of the most interesting aspects of the condition because we don’t actually know how to tell if a person has Synesthesia. There’s no clinical diagnosis for the condition, and the condition isn’t widely studied. This means that a lot of researchers don’t agree on standards for what constitutes Synesthesia or not. For example, some researchers argue that everyone is born with Synesthesia to different extents because of the hyperconnectivity of our infant brains, then as these connections are pruned, Synesthesia decreases over time.
Despite these differences, there are some tests that help us to gauge the extent to which a person may or may not have Synesthesia. Like the “The Synesthesia Battery”. What it’s important to note is that to have Synesthesia, a person’s experience of multiple senses being triggered must be consistent over time. If hearing a certain sound, like a bicycle bell, triggers another sensory experience, like seeing the colour blue, five times and that’s it. That isn’t Synesthesia. Yet if you have that experience every single time for the past decade then you might have the condition.
Clinical Psychology Conclusion
Something that I found really interesting about this episode was just how little information there is out there about Synesthesia. I was expecting to be able to find tons of peer-reviewed and high-quality information on causes, treatments and other aspects of the condition, but I couldn’t. I suppose my expectations were biased because my norm reference was the number of times that I’ve seen this condition mentioned in the BPS Research Digest, but in reality, this is still a very understudied condition.
Therefore, I hope that there is more research done in the future because this is a profound condition that must be rather scary for individuals to experience. If the condition isn’t causing these individuals distress and impaired functioning, then we shouldn’t look to treat it or pathologise it. In fact, one reason why I want there to be more research into the condition is because I strongly believe that by learning about perception and sensory experiences in people with an atypical representation, as seen in Synesthesia, then it can help us understand perception and our senses more as a whole. Therefore, the more we understand Synesthesia, the more likely we are to make connections and other insights that are useful in our overall understanding of perception.
Hopefully, these additional research findings will have future clinical implications and might be useful in helping us treat different conditions with sensory or perception elements.
Just some thoughts but this has been a fun, insightful and interesting podcast episode.
I really hope you enjoyed today’s cognitive psychology podcast episode.
If you want to learn more, please check out:
Cognitive Psychology: A Guide to Neuropsychology, Neuroscience and Cognitive Psychology. Available from all major eBook retailers and you can order the paperback and hardback copies from Amazon, your local bookstore and local library, if you request it. Also available as an AI-narrated audiobook from selected audiobook platforms and library systems. For example, Kobo, Spotify, Barnes and Noble, Google Play, Overdrive, Baker and Taylor and Bibliotheca.
Have a great day.
Cognitive Psychology References and Further Reading
Anash, S., Boileau, A., & Boileau, A. J. (2024). Grapheme-color synesthesia and its connection to memory. Cureus, 16(8).
Eckardt, N., Sinke, C., Bleich, S., Lichtinghagen, R., & Zedler, M. (2024). Investigation of the relationship between neuroplasticity and grapheme-color synesthesia. Frontiers in Neuroscience, 18, 1434309.
https://www.psychologytoday.com/us/basics/synesthesia
Murray, R. (2021). A review of Synesthesia: historical and current perspectives. Murray UWL J. Undergrad. Res, 24.
Rahimian, Z., Jahangiri, S., Mehrian, S. R. A., Akbari, M., MosalamiAghili, S., Ghahramani, Z., ... & Behbood, A. (2026). Synesthesia and associated clinical conditions: A comprehensive review of current evidence. Heliyon, 12(14).
Ward, J., & Simner, J. (2020). Synesthesia: The current state of the field. In Multisensory perception (pp. 283-300). Academic Press.
Ward, J., & Simner, J. (2022). How do different types of synesthesia cluster together? Implications for causal mechanisms. Perception, 51(2), 91-113.
Winter, B., & Strik-Lievers, F. (2025). Linguistic synesthesia: A meta-analysis. Cambridge University Press.
Zhao, Q., Ahrens, K., & Huang, C. R. (2022). Linguistic synesthesia is metaphorical: a lexical-conceptual account. Cognitive Linguistics, 33(3), 553-583.
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