Seeing Sounds and Hearing Colors: Psychedelics & Synesthesia

What is Synesthesia?

Synesthesia is one of the brain’s strangest magic tricks—a neurological crossover where one sense hijacks another. It’s the experience of seeing sounds, tasting colors, or feeling music on your skin. These cross-sensory fusions aren’t poetic metaphors—they’re perceptually real. The number “3” might shimmer green. Wednesday might feel like velvet and smell faintly of rain. A specific musical note might appear as blue.

For individuals known as synesthetes, sensory overlap is consistent and automatic. The term synesthesia comes from the Greek syn (together) and aesthesis (perception). Scientists define it as the involuntary activation of one sensory pathway by another. Artists define it as proof that reality is far less stable than we think. Both are right.

Studies show synesthesia arises from atypical cross-communication between sensory regions—essentially, the brain’s wiring diagram is a little more entangled than average. Imaging studies reveal that synesthetes often show enhanced connectivity between visual, auditory, and emotional cortices, allowing sensory boundaries to blur. Their brains are not malfunctioning; they’re over-communicating (Luke & Terhune, 2013; Luke et al., 2022).

And while synesthesia is typically lifelong, it’s also a lens for understanding creativity itself. Many synesthetes excel in art and music, where sensory fusion becomes a language—one that most of us only glimpse in dreams, fever states, or…under psychedelics.

Psychedelics: Catalysts for Perceptual Crossfire

So what happens when these two worlds—the naturally synesthetic and the pharmacologically induced—collide? Research and countless first-hand reports suggest that psychedelics can induce synesthetic-like experiences even in those who’ve never had them before.

Psychedelics—LSD, psilocybin, DMT—are the mind’s “debugging tools,” revealing how perception is built by temporarily breaking it. Under their influence, the senses begin to dance with each other. Sounds shimmer. Emotions have texture. Time bends its elbows and drips.

Pharmacologically, these substances activate the brain’s serotonin 5-HT2A receptors, creating a neural fireworks show of disinhibition and connectivity. Areas that usually operate separately start chatting—visual, auditory, emotional, and associative networks form what some neuroscientists call a “hyperconnected brain.”

This temporary rewiring may mimic, or even amplify, the mechanisms seen in natural synesthesia. Both involve crosstalk between sensory cortices. Both heighten the unity of perception. And both collapse the neat borders we normally draw between “self” and “world.” In short: psychedelics turn everyone into a temporary synesthete.

Brain imaging studies support this: psychedelics appear to increase global neural connectivity, particularly between the visual, auditory, and emotional cortices. When these systems start talking to each other outside their normal lanes, perception becomes more unified, fluid, and multidimensional. In essence, psychedelics can simulate—or temporarily unlock—a form of synesthetic perception.

For true synesthetes, psychedelics can amplify their existing crossovers. For others, the experience serves as a revelation: a direct, visceral demonstration that perception isn’t a passive window but an active, creative construction of the mind. That realization can be profoundly destabilizing—or deeply enlightening—depending on one’s perspective.

Neuroscience: Where Chemistry Meets Perception

Both synesthesia and psychedelic states challenge our fundamental model of how the brain “binds” sensory information into coherent experience. Normally, perception is modular: visual data goes to the occipital lobe, sound to the temporal, touch to the somatosensory cortex. The brain integrates these signals into a unified whole through intricate timing and feedback mechanisms. But under psychedelics, those boundaries relax. Hierarchical control weakens; bottom-up sensory data floods the system.

Reports from psychedelic experiences consistently describe vivid sensory blending: music exploding into fractal geometry, voices blooming in color, emotions pulsing as temperature shifts. These experiences, far from random, reveal how perception itself is constructed — not as passive input, but as a generative hallucination sculpted by the brain.

Modern neuroimaging supports this. Studies using MRI, EEG and MEG show that psychedelics increase communication between brain regions that are normally isolated and flatten the brain’s usual network structure, allowing for hyperconnectivity—regions that rarely interact start to synchronize. When the auditory cortex starts whispering to the visual cortex, you get “seeing sounds.” When emotional centers sync with tactile ones, you “feel” music. It’s no coincidence that users report hearing colors and seeing sounds. The visual and auditory cortices may literally be firing together, producing experiences that feel cross-modal because they are.

This neural “entropy” isn’t random chaos. It may reveal an underlying flexibility—a latent potential—in how perception is wired. The same mechanisms that produce hallucinations could also explain creativity, metaphor, and dream imagery. After all, the poetic idea of “a loud red” or “a bitter melody” may originate from the same neural bridges that psychedelics temporarily reopen.

These findings suggest that psychedelic synesthesia isn’t just a side effect—it’s a window into the neural fabric that binds experience together. In this light, perception is less a camera and more a painter—and psychedelics simply let us watch the brushstrokes happen in real time.

Beyond the Trip: What These States Teach Us

Understanding how psychedelics induce synesthetic perception isn’t just philosophically trippy; it’s scientifically valuable. It provides insight into sensory binding, neural plasticity, and consciousness itself. When perception breaks its own rules, we glimpse the machinery behind the curtain. Both natural synesthesia and psychedelic states point toward the same truth: our senses are not separate rooms in the mansion of the mind—they’re overlapping doorways. To see sound or hear color is to glimpse, however briefly, how deeply the brain wants to unify the world.

In clinical contexts, this hyperconnected state might even facilitate emotional breakthroughs and creative insights—the kind of “aha” moments that change people’s lives. In psychedelic-assisted therapy, enhanced sensory cross-talk might actually facilitate emotional integration. The sensory richness and fluidity of these states can help people reframe memories, confront trauma, and form new emotional associations. A traumatic image might be experienced as color or sound, processed symbolically rather than directly—a kind of neural poetry that allows the psyche to translate pain into pattern.

Synesthesia, in this light, becomes more than a curiosity; it’s a model for how perception and emotion intertwine to create subjective reality. Psychedelics simply turn up the volume on that process, allowing us to study—and perhaps harness—it.

Perception Unbound

Ultimately, both synesthesia and psychedelics challenge the assumption that our senses offer a fixed, objective map of reality. They remind us that perception is an act of creation, shaped by the brain’s unique wiring and chemistry. Seeing sounds or feeling colors isn’t “wrong”—it’s the mind demonstrating just how elastic the boundaries of experience can be.

As neuroscience continues to explore the psychedelic renaissance, the synesthetic parallels offer a bridge between art, science, and consciousness itself. Whether born or induced, these experiences reveal a simple truth: the brain doesn’t merely receive the world—it composes it. And if that composition occasionally hums in technicolor or sings in shapes, maybe that’s not madness at all—maybe it’s insight.

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Resources

Luke, D. P., & Terhune, D. B. (2013). The induction of synaesthesia with chemical agents: a systematic review. Frontiers in psychology, 4, 753. https://doi.org/10.3389/fpsyg.2013.00753 

Luke, D. P., Lungu, L., Friday, R., & Terhune, D. B. (2022). The chemical induction of synaesthesia. Human psychopharmacology, 37(4), e2832. https://doi.org/10.1002/hup.2832