A woman hears the word “Derek” and immediately tastes earwax.

Another person sees the number 5 as inherently, unavoidably red. Not because of any association or memory—it’s just red, the way the sky is blue.

A musician feels violin notes as textures on his skin—high notes feel smooth and cool, low notes feel rough and warm.

A painter sees every letter and number in specific colors. A is red, B is blue, C is yellow. She’s never seen them any other way.

These aren’t metaphors. They’re not associations or memories or poetic descriptions.

They’re synesthesia—a neurological condition where sensory experiences cross in ways that shouldn’t be possible.

And for synesthetes, it’s not unusual or strange. It’s just how the world is.

What Is Synesthesia?

Synesthesia is a blending of sensory experiences.

In most people, sensory pathways are separate: visual information is processed as vision, auditory as sound, taste as taste.

In synesthetes, these pathways cross. Stimulating one sense automatically triggers experiences in another sense.

The most common form is grapheme-color synesthesia: seeing letters and numbers as inherently colored.

But synesthesia takes many forms:

Chromesthesia: Sounds trigger color experiences. Music becomes a visual display.

Lexical-gustatory synesthesia: Words trigger taste sensations.

Mirror-touch synesthesia: Seeing someone touched triggers tactile sensations on your own body.

Spatial sequence synesthesia: Numbers, months, or days of the week have specific spatial positions in space around you.

Sound-to-touch synesthesia: Sounds create physical sensations.

About 4% of people have some form of synesthesia, though many don’t realize it’s unusual until adulthood.

It’s Not Metaphorical

The key thing to understand: synesthesia isn’t imagination or association.

When a grapheme-color synesthete sees the number 5, they experience red. Not “it reminds me of red” or “I associate it with red.”

They see red. As automatically and unavoidably as you see the actual color of the ink on the page.

When a lexical-gustatory synesthete hears the word “Derek,” they taste earwax. Not a memory of earwax. Actual taste, in their mouth, as real as if they’d put something in their mouth.

Brain imaging confirms this: when synesthetes experience their cross-sensory perceptions, the corresponding brain regions activate.

A person hearing sounds that trigger color experiences shows activation in their visual cortex—the same region that activates when actually seeing colors.

This isn’t imagination. It’s genuine sensory experience, triggered through an unusual neural pathway.

The Consistency

What makes synesthesia scientifically credible is its consistency.

If you test a grapheme-color synesthete today and ask them what color the number 7 is, they’ll say “yellow” (or whatever color they experience).

Test them again in a week, a month, a year—without warning, without preparation—and they’ll give the same answer.

7 is always yellow. It’s been yellow their entire life. It will be yellow tomorrow.

This consistency is automatic and involuntary. Synesthetes don’t have to remember their associations—they just experience them.

Non-synesthetes trying to fake synesthesia can’t maintain this consistency over time. Their “associations” drift and change because they’re not based on genuine sensory experience.

Growing Up Synesthetic

Many synesthetes don’t realize their experiences are unusual until surprisingly late in life.

If you’ve always experienced letters as colored, you assume everyone does.

A synesthetic child might say “that’s wrong” when shown a number printed in the “wrong” color. The number 5 printed in blue feels incorrect, jarring, like seeing a misspelled word.

The child assumes everyone feels this way. Why wouldn’t they?

It’s only when someone says “what do you mean the number has a color?” that the synesthete realizes: oh, this isn’t universal.

One woman discovered her synesthesia in her 30s during a conversation about memory techniques.

She mentioned that she remembers phone numbers by their colors. Someone asked what she meant. She explained that numbers have colors, so phone numbers form color patterns she can remember visually.

Everyone stared at her.

“Numbers don’t have colors,” someone said.

Her entire reality shifted. She’d spent 30+ years assuming everyone saw what she saw.

The Advantages

Synesthesia can provide cognitive advantages:

Enhanced memory: Synesthetes often have exceptional memory because they encode information multi-modally. A number isn’t just a number—it’s a number with a color, giving an extra dimension for recall.

Pattern recognition: Cross-sensory experiences can help identify patterns others might miss. Numbers form color sequences. Sounds create visual landscapes that reveal musical structure.

Creativity: Many artists, musicians, and writers have synesthesia. The cross-sensory experiences provide rich material for creative work.

Composer Olivier Messiaen had chromesthesia—he saw music as colors. He composed based on the color relationships he experienced, creating works that translate his synesthetic experience into sound.

Painter Wassily Kandinsky also had synesthesia and tried to paint the music he heard, creating visual representations of synesthetic sound-color experiences.

The Downsides

But synesthesia can also be overwhelming:

Sensory overload: If sounds trigger colors, a noisy environment becomes a visual assault. Too much sensory information to process.

Distraction: Strong cross-sensory experiences can be distracting. A lexical-gustatory synesthete might struggle to focus on conversation if certain words trigger unpleasant tastes.

Social misunderstanding: Explaining synesthetic experiences to non-synesthetes often leads to confusion or disbelief. “You taste words? That doesn’t make sense.”

Cognitive conflict: When the synesthetic experience contradicts external reality. A number printed in the “wrong” color creates dissonance—you see blue ink but experience the number as red.

Mirror-Touch: Feeling Others’ Experiences

One of the most fascinating forms is mirror-touch synesthesia.

Mirror-touch synesthetes physically feel what they see others experiencing.

They see someone brush their arm, and they feel the touch on their own arm.

They watch someone get injured, and they feel pain in the corresponding location on their own body.

This isn’t empathy in the normal sense. It’s not imagining how it feels. It’s genuine tactile sensation triggered by observation.

Brain imaging shows that mirror-touch synesthetes have heightened activity in brain regions responsible for processing touch (somatosensory cortex) when observing others being touched.

For most people, this system is partially activated when watching others (the basis of empathy and learning by observation) but inhibited from creating actual sensation.

In mirror-touch synesthetes, the inhibition is reduced. The observation creates full-fledged tactile experience.

The Implications for Empathy

Mirror-touch synesthesia raises questions about the neurological basis of empathy.

All humans have some capacity to feel what others feel—that’s how we understand others’ emotions and experiences.

But in most people, it’s abstract or suppressed. We imagine how it feels; we don’t literally feel it.

Mirror-touch synesthetes experience a more direct, visceral version of empathy.

They can’t watch suffering without physically feeling it. They can’t observe touch without experiencing it on their own skin.

This suggests that empathy exists on a spectrum, from abstract understanding to literal shared sensation.

Most people are somewhere in the middle. Mirror-touch synesthetes are at the extreme end.

The Neuroscience

Why does synesthesia happen?

The leading theory: cross-wiring in sensory processing regions.

In typical brain development, sensory regions are initially interconnected. As the brain matures, many of these connections are pruned away, leaving specialized, separate sensory pathways.

In synesthetes, some of these connections remain or are over-abundant.

The grapheme-processing region (which recognizes letters and numbers) sits adjacent to the color-processing region (V4 in the visual cortex).

In grapheme-color synesthetes, there’s increased connectivity between these regions. Activating one automatically activates the other.

Similarly, the auditory cortex and visual cortex have connections that are normally suppressed. In chromesthetes (sound-to-color synesthesia), these connections are stronger.

The result: stimulating one region spills over into another, creating cross-sensory experiences.

Is It Advantageous or Disordered?

This raises an interesting question: is synesthesia a condition or a variation?

It’s not pathological. Synesthetes aren’t impaired (though it can sometimes be overwhelming). Many function excellently and consider their synesthesia an advantage.

But it’s also unusual—only about 4% of people have it.

Is it a neurological difference, like being left-handed? Or a mild disorder, like color blindness?

Most synesthetes and researchers consider it a variation—a different way of experiencing the world, not better or worse, just different.

Some synesthetes say they can’t imagine living without their cross-sensory experiences. It would be like losing a sense.

Others, particularly those with overwhelming forms like intense lexical-gustatory synesthesia, wish they could turn it off.

Acquired Synesthesia

While most synesthesia is developmental (present from early childhood), it can occasionally be acquired:

Drug-induced: LSD, psilocybin, and mescaline can trigger temporary synesthetic experiences. Sounds become visual, colors have textures, music creates tactile sensations.

After brain injury: Damage to certain brain regions can sometimes produce synesthesia, likely by disrupting normal inhibitory pathways that keep senses separate.

After vision loss: Some people who lose vision develop auditory-to-visual synesthesia, where sounds create visual experiences. The brain, deprived of visual input, starts interpreting auditory information as visual.

Acquired synesthesia is usually less consistent than developmental synesthesia and sometimes fades over time.

The Philosophical Implications

Synesthesia raises profound questions about the nature of perception:

How arbitrary are our sensory categories?

We divide the world into sight, sound, taste, touch, smell. But those divisions are constructions of how our brains process information.

Synesthetes experience a world where those boundaries blur. Sound is color. Words are tastes. Touch is shared across observers.

Maybe our typical separation of senses is the unusual thing, and synesthetes experience a more integrated sensory reality.

Is there a “correct” way to experience reality?

A grapheme-color synesthete sees 5 as red. You see 5 as black (or whatever color it’s printed in).

Who’s right? The synesthete is experiencing genuine perception—it’s not imagined or voluntary.

But it doesn’t correspond to external reality. The number 5 doesn’t emit red light.

So whose experience is “real”? Both are real subjective experiences. Neither corresponds to objective “true” properties of numbers.

Maybe all perception is like this—our brains construct experiences that are real to us but don’t necessarily correspond to objective reality.

Living in More Dimensions

Synesthetes sometimes describe feeling like they experience the world in more dimensions than non-synesthetes.

A number isn’t just a symbol—it’s a symbol with color, possibly with spatial position, possibly with personality or emotional quality.

Music isn’t just sound—it’s sound with color, possibly with texture, possibly with taste.

Words aren’t just meanings—they’re meanings with flavor, with color, with shape.

It’s a richer, more complex sensory world.

But also potentially more overwhelming. More information to process. More dimensions to navigate.

The Synesthete’s Dilemma

The challenge synesthetes face is one of translation:

How do you explain to a non-synesthete what it’s like to taste words?

How do you convey the experience of seeing music as color?

Language is built on shared experiences. We can communicate about “red” because most people experience red similarly.

But synesthetic experiences have no common reference. Non-synesthetes have never tasted a word or seen a number as colored (except artificially, in printed materials).

So synesthetes live with experiences they can’t fully communicate. An internal sensory richness that others can understand intellectually but never experience.

The Questions That Remain

Despite extensive research, mysteries remain:

Why these specific cross-wirings?

Why is grapheme-color synesthesia common but grapheme-smell synesthesia rare?

Why does sound often trigger color but rarely trigger taste?

Is there a pattern to which sensory combinations occur, or is it random?

What determines the specific associations?

Why does one synesthete experience 5 as red while another experiences it as green?

The consistency within each synesthete is absolute, but the variation between synesthetes is enormous.

Can synesthesia be induced or trained?

Some research suggests that extensive training can create synesthesia-like experiences. People who practice extensively with number-color associations sometimes develop automatic color experiences for numbers.

Is this real synesthesia, or just very strong learned associations?

What does it reveal about consciousness?

If synesthetes experience colors when hearing sounds, are they experiencing something that “really” exists but non-synesthetes can’t access?

Or are they experiencing brain-generated illusions that happen to be consistent and automatic?

The Beauty of Difference

Perhaps the most important lesson from synesthesia:

Perception is not universal. Reality is experienced differently by different brains.

What you see, hear, taste, smell, and feel is a construction of your nervous system. It’s real—it’s the realest thing you know.

But it’s not the same as what everyone else experiences.

Synesthetes live in a world that’s simultaneously the same and completely different from the world non-synesthetes inhabit.

Same physical stimuli. Radically different experiences.

And neither way is more “correct.” They’re just different paths through the same reality.

The number 5 exists objectively.

But whether it’s red or blue or colorless depends entirely on the nervous system observing it.

And that’s both strange and beautiful.

Medical Sources:

  • Cytowic, R. E., & Eagleman, D. M. (2009). Wednesday Is Indigo Blue: Discovering the Brain of Synesthesia. MIT Press.
  • Ramachandran, V. S., & Hubbard, E. M. (2001). “Synaesthesia–a window into perception, thought and language.” Journal of Consciousness Studies, 8(12), 3-34.
  • Ward, J. (2013). “Synesthesia.” Annual Review of Psychology, 64, 49-75.
  • Simner, J., & Hubbard, E. M. (Eds.). (2013). The Oxford Handbook of Synesthesia. Oxford University Press.

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