Identify the major clusters of synesthesia and describe how they are grouped based on shared sensory experiences
Analyze how the presence of multiple synesthesia clusters supports theories about shared or distinct causal mechanisms in the brain
Interpret the significance of "island" types of synesthesia (e.g., mirror-touch, ticker-tape) and evaluate their role in the broader synesthesia spectrum
Key Terms
perception
way that sensory information is interpreted and consciously experienced
Tasting Words and Hearing Colors
Kai always knew their mind worked a little differently. When they read the word Tuesday, they tasted mint. Numbers had personalities. Music shimmered in colors. At first, they thought it was just their imagination. But during a psychology lecture on synesthesia, Kai realized their experiences were part of a fascinating neurological phenomenon.
Curious, Kai joined a university study investigating how different types of synesthesia cluster together. The researchers asked them to complete a detailed questionnaire covering dozens of synesthetic experiences, including:
grapheme-color synesthesia: when visual aspects correspond with color sensations
lexical-gustatory synesthesia: when words correspond with taste sensations
mirror-touch synesthesia: when a person can feel a touch sensation on their own body when they see someone else touched
ticker-tape synesthesia: when a person sees written words, or "subtitles," when hearing words
As the data came in, Kai learned that their experiences weren't random. They fit into specific clusters, or groups of synesthesia types that tend to co-occur. The study aimed to uncover whether these clusters pointed to shared causal mechanisms in the brain.
1. On Your Own
Synesthesia Clusters
The researchers used hierarchical clustering analysis to group synesthesia types based on co-occurrence patterns.
Kai's grapheme-color synesthesia, where letters and numbers evoke specific colors, placed them in the language-color cluster. For example, Kai always saw the letter A as red and the number 5 as green, even if they were printed in black.
Lea, another person in the study, reported sequence-space synesthesia, where she visualized months and numbers in spatial arrangements; this placed her in the sequence-space cluster. In Lea's mind, the months of the year formed a loop, with January at the top and December curving around to the left.
Jaya reported ordinal-linguistic personification, part of the personification cluster. To her, Monday was a grumpy old man, while Friday felt like a cheerful teenager.
Oliver's experience of seeing colors when hearing music, like purple swirls when a violin played, was part of the visualized sensations cluster, specifically sound-color synesthesia.
Finally, Mina described a rare but vivid experience: When she heard the word calendar, she tasted cherry cough syrup. This placed her in the language-taste cluster, a form of lexical-gustatory synesthesia.
These clusters helped researchers understand that synesthesia isn't just a collection of isolated traits; it's a network of interconnected sensory experiences, often shaped by shared brain mechanisms.
Explore the Concept
Discover how synesthesia blends the senses in this short video.
2. On Your Own
Provide each cluster with the synesthesia type it includes in the following table. Remember to print your work before leaving this page!
Cluster
Synesthesia Type
language-color cluster
personification cluster
visualized sensations cluster
Causal Mechanisms
Kai was fascinated to learn that these clusters might reflect different causal mechanisms, some possibly genetic and others developmental. The study also found that ticker-tape synesthesia, where people see a mental "subtitle" of their thoughts, didn't fit neatly into any cluster. This could mean it has a unique origin or has weak correlations to other forms of synesthesia, suggesting it could represent a distinct or more isolated phenomenon within the broader spectrum of synesthesia.
The findings challenge the idea that synesthesia is a single condition. Instead, it may be a family of related phenomena, each with its own neurological roots.
3. On Your Own
Synesthesia Simulator
Engage with this synesthesia simulator to explore what it might be like to have a form of synesthesia.
Perceptions and Reality
Kai's journey helped them see that their unique perceptions weren't just quirks; they were part of a broader neurological pattern. The study gave them insight into how the brain weaves together senses and how science is just beginning to understand the rich tapestry of human perception.
Reflect & Respond
Answer the following questions to reflect on key ideas from the case study. Remember to print your work before leaving this page!
How might the clustering of synesthesia types influence how we define and identify neurological diversity?
Consider whether synesthesia should be viewed as a single condition or a collection of related phenomena.
What do the findings about distinct synesthesia clusters suggest about how the brain processes sensory information? Think about how this might relate to broader topics like perception, memory, or creativity.
If you were designing a follow-up study, what question(s) would you want to explore about synesthesia, and why?
Propose a hypothesis or method that could build on clustering research.
Ward, J., & Simner, J. (2022). How do different types of synesthesia cluster together? Implications for causal mechanisms. Perception, 51(2), 91–113.https://doi.org/10.1177/03010066211070761 This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC-BY 4.0).
Photo Credits
lexiconimages on Adobe Stock. "synesthesia word or concept represented by wooden letter tiles on a wooden table with glasses and a book."
freshidea on Adobe Stock. "Neural Pathways and brain intelligence as a cognitive function and psychiatric or psychological behavior or neurological disorder symbol as a human thinking organ as ropes as a mental health icon."
Pixel-Shot on Adobe Stock. "Thoughtful young African-American woman and listed types of neuro-linguistic programming (NLP) on grey background."
