Most people cannot simply decide to become synesthetes, but research over the past decade has shown that structured training can produce experiences that resemble genuine synesthesia in at least some individuals. In one widely cited study, non-synesthetic adults who completed weeks of adaptive reading and memory exercises began reporting color experiences when looking at plain black letters, both inside and outside the lab. The gap between “real” synesthesia and what training can achieve is narrower than scientists once assumed, though it is still very much a gap. Understanding what works, what does not, and what the brain is actually doing when senses start to cross over can help you decide whether pursuing these experiences is realistic or worthwhile.
What Synesthesia Actually Is (and What It Is Not)
Synesthesia is an involuntary, consistent pairing of sensory or cognitive channels: hearing a note and automatically seeing a color, reading the number 5 and always perceiving it as green, or feeling a texture when tasting certain foods. The key features that separate it from imagination or metaphor are automaticity (you do not choose it) and consistency (the same trigger produces the same concurrent experience over months and years). Roughly three to four percent of the population has some form of it, though estimates vary depending on how strictly researchers define the condition.
Everyone, however, has cross-modal associations. The classic example is the bouba/kiki effect: when shown a rounded blob and a jagged star shape, the vast majority of people match the round shape with the nonsense word “bouba” and the spiky shape with “kiki.” This is not synesthesia, but it demonstrates that your brain already links information across senses in systematic ways. The question for someone interested in synesthetic experiences is whether those latent connections can be strengthened into something closer to the real thing.
Training Your Brain to See Letters in Color
The most well-studied route to synesthesia-like experiences is associative training, specifically for grapheme-color synesthesia (seeing letters or numbers in color). Researchers at the University of Sussex designed an intensive program in which participants read specially formatted books where specific letters were always printed in the same color. Over the course of several weeks, subjects completed adaptive memory and reading tasks reinforcing 13 letter-color pairings. After the training period, participants showed standard behavioral and physiological markers associated with grapheme-color synesthesia, and most reported actually perceiving colors when looking at achromatic letters, both during experiments and in everyday life.1PubMed Central. Adults can be trained to acquire synesthetic experiences
A separate study using a similar colored-reading approach found that after the training period, participants showed interference effects when letter colors conflicted with the trained associations, meaning their brains were processing the trained colors automatically enough to slow down reaction times when a mismatch occurred.2PLoS ONE. Pseudo-Synesthesia through Reading Books with Colored Letters Follow-up neuroimaging work confirmed that training-induced synesthetic experiences were accompanied by cortical changes characteristic of genuine synesthesia.3PubMed. Coordinated neural, behavioral, and phenomenological changes in perceptual plasticity through overtraining of synesthetic associations
The researchers behind these studies are careful with their claims. They acknowledge that the method does not cause every participant to develop grapheme-color synesthesia, only that certain individuals can form letter-color associations through this process, and that these associations share features with developmental synesthesia.4PubMed Central. Training synesthetic letter-color associations by reading in color In practical terms, this means the technique is real but not guaranteed. Some people respond to the training more than others, and we do not yet know what separates responders from non-responders.
How to Try Colored-Reading Training Yourself
If you want to experiment with this approach at home, the basic framework is straightforward. You pick a consistent set of letter-color assignments (A is always red, B is always blue, and so on) and then read text where those letters are rendered in their assigned colors. You do this daily for weeks, ideally while also doing memory tasks that reinforce the associations. Several free browser extensions and apps now exist that can recolor text on web pages according to a fixed mapping.
A few practical points matter. First, consistency is everything. The same letter must always appear in the same color. If you change mappings partway through, you undermine the entire process. Second, duration matters. The studies that produced genuine phenomenological changes involved weeks of daily practice, not a few sessions. Third, manage your expectations. The literature suggests that what most people develop is better described as “pseudo-synesthesia” or trained associations rather than the full-blown involuntary experience that developmental synesthetes report. You may start noticing faint color impressions when you see certain letters, but it is unlikely to be as vivid or automatic as what someone born with the trait experiences.
Why Some People Have Synesthesia Naturally
Developmental synesthesia, the kind people are born with, appears to arise from differences in how the brain prunes its neural connections during early childhood. Infants are born with far more synaptic connections than adults retain. During the first years of life, unused or redundant connections get trimmed back through a process called synaptic pruning. One leading hypothesis holds that synesthetes retain extra cross-modal connections that most people lose.
A study testing this “incomplete pruning” hypothesis found that synesthetes were significantly better than control participants at discriminating nonnative speech sounds and distinguishing chimpanzee faces, abilities that are normally lost during infant development as the brain specializes. The fact that synesthetes retained these broader perceptual abilities across multiple sensory domains supports the idea that their brains maintained connections that most people’s brains eliminated in early life.5PubMed Central. Reduced perceptual narrowing in synesthesia
Another model focuses not on extra wiring but on disinhibited feedback. In typical brains, higher-order brain regions send feedback signals to primary sensory cortices, but these signals are normally kept in check. In synesthetes, that inhibition may be weakened, allowing sensory information to flow more freely between regions. Neuroimaging of auditory-visual synesthetes found stronger connectivity between parietal cortex and both auditory and visual areas, supporting this feedback model.6PubMed. Disinhibited feedback as a cause of synesthesia: evidence from a functional connectivity study on auditory-visual synesthetes Some researchers have proposed that a multisensory hub at the junction of the temporal, parietal, and occipital lobes plays a role in this disinhibited feedback.7Neuron. Toward a neurobiology of synesthesia
These two models are not mutually exclusive. Some synesthetes may have extra physical connections; others may have normal wiring with unusual feedback dynamics. Either way, the underlying biology is largely set during development and influenced by genetics.
The Genetic Factor
Synesthesia runs in families, and genetic studies have identified several chromosomal regions linked to the trait. Linkage analyses of families with colored-sequence synesthesia found suggestive evidence pointing to a region on chromosome 16.8PubMed Central. The genetics of colored sequence synesthesia: Suggestive evidence of linkage to 16q and genetic heterogeneity for the condition A broader whole-genome scan of families with auditory-visual synesthesia identified linkage to four different chromosomal regions, leading researchers to conclude that synesthesia is likely influenced by multiple genes under different modes of inheritance rather than a single gene.9American Journal of Human Genetics. A Whole-Genome Scan and Fine-Mapping Linkage Study of Auditory-Visual Synesthesia Reveals Evidence of Linkage to Chromosomes 2q24, 5q33, 6p12, and 12p12
More recently, whole-exome sequencing of three families with sound-color synesthesia identified rare variants in six genes involved in axonogenesis, the process by which nerve cells extend their connections during brain development. These genes are expressed during early childhood, precisely when synesthetic associations typically form.10PubMed Central. Rare variants in axonogenesis genes connect three families with sound-color synesthesia This finding ties the genetics directly back to the hyperconnectivity hypothesis: the genes involved are literally the ones that build neural wiring during development.
For someone hoping to develop synesthesia, the genetic evidence is sobering but not a dead end. It suggests that developmental synesthesia involves a biological predisposition you either have or do not. But the training studies show that at least some synesthesia-like experiences can be cultivated regardless of genetic background, even if the experience differs in intensity from the developmental form.
Psychedelics and Synesthetic Experiences
Psychedelic substances are probably the most commonly discussed shortcut to synesthesia-like perception, and the link is real. LSD, psilocybin, and mescaline reliably produce cross-sensory blending in many users, such as “seeing” music or perceiving textures in response to sounds. A systematic review comparing the phenomenology of LSD and psilocybin found that at medium doses, LSD produced significantly higher scores than psilocybin on measures of audio-visual synesthesia, complex imagery, and changed meaning of percepts.11Nature. Synergistic, multi-level understanding of psychedelics: three systematic reviews and meta-analyses of their pharmacology, neuroimaging and phenomenology
There is, however, a distinction worth drawing. Psychedelic synesthesia is temporary, unpredictable in its specifics, and depends on the pharmacological state of the brain rather than any lasting structural change. When the drug wears off, the cross-sensory experiences stop. A developmental synesthete who always sees Tuesday as orange does not need a substance to trigger the perception, and the association stays exactly the same across decades. Psychedelic-induced cross-sensory experiences are closer to a demonstration of what unusual neural crosstalk feels like than a pathway to permanent synesthesia.
That said, some researchers speculate that psychedelic experiences could potentially serve as a “window” that helps people understand what cross-sensory connections feel like, and possibly prime the brain for associative training. This idea is speculative and has not been tested in controlled studies linking psychedelic use to subsequent training outcomes.
Hypnosis as a Route to Synesthetic Perception
Hypnotic suggestion has also been shown to induce experiences that share features with synesthesia. A study found that hypnosis could rapidly produce the kind of targeted, preconsciously triggered associations and perceptual changes seen in congenital synesthesia.12Scientific Reports. Synaesthesia-type associations and perceptual changes induced by hypnotic suggestion Participants under hypnosis showed interference effects similar to those seen in genuine synesthetes, suggesting that the perceptual changes were not just imagined but were influencing how the brain processed sensory information.
Hypnosis has an obvious limitation as a practical approach: the effects typically last only as long as the hypnotic state. And susceptibility to hypnosis varies widely. Roughly 10 to 15 percent of the population is highly hypnotizable, while many people respond minimally. So while hypnosis confirms that the brain can be nudged into synesthesia-like processing, it is not a reliable path for most people seeking lasting cross-sensory experiences.
Brain Stimulation and Sensory Substitution Devices
Non-invasive brain stimulation techniques offer another angle. Researchers used transcranial direct current stimulation (tDCS) to increase excitability of the somatosensory cortex in non-synesthetic participants. After stimulation, participants showed interference effects that mimicked mirror-touch synesthesia: they became slower at localizing a touch on their own hand when simultaneously watching someone else’s hand being touched, a pattern characteristic of people who genuinely feel touches they observe on others.13Current Biology. Induction of Mirror-Touch Synaesthesia by Increasing Somatosensory Cortical Excitability Like hypnosis, though, these effects are temporary and require specialized equipment.
Sensory substitution devices take a different approach entirely. These devices convert information from one sense into another, typically translating visual information into sound or touch patterns for people who are blind or deaf. Neuroimaging studies of people using these devices have shown that visual brain regions become activated by auditory or tactile input, demonstrating that the adult brain can reorganize and repurpose cortical areas for novel sensory inputs through structured practice.14PubMed Central. Use of sensory substitution devices as a model system for investigating cross-modal neuroplasticity in humans While this is not synesthesia in the traditional sense, it demonstrates that sustained cross-modal training can produce genuine neural reorganization even in adult brains.
Sensory Deprivation and Cross-Modal Plasticity
Temporarily removing one sense can enhance the brain’s reliance on others, and there is evidence that even short-term sensory deprivation promotes cross-modal flexibility. A study found that participants who were blindfolded for a period showed significantly greater proprioceptive recalibration compared to a non-blindfolded control group.15Nature. Short-term visual deprivation boosts the flexibility of body representation The blindfolded group’s brains became more responsive to touch-based spatial information, suggesting that reducing visual input frees up neural resources for other sensory processing.
This principle is consistent with cases of acquired synesthesia following sensory loss. Acquired auditory-visual synesthesia has been reported in people who lost vision due to optic nerve damage, with the brain’s visual cortex becoming activated by sounds.16PubMed. Seeing the sound after visual loss: functional MRI in acquired auditory-visual synesthesia Acquired synesthesia has also been reported in association with temporal lobe pathology and deafferentation of the visual system more broadly.17PubMed Central. Acquired auditory-visual synesthesia: A window to early cross-modal sensory interactions Even a congenitally blind man has been documented as having synesthesia involving numbers, letters, months, and days of the week, each linked to specific positions in mental space and specific tactile textures, proving that synesthesia can develop without any visual experience at all.18PubMed. Synesthesia in a congenitally blind individual
For someone with normal sensory function, this does not mean you should blindfold yourself for weeks hoping for synesthetic experiences. But it does highlight how remarkably flexible the brain remains, and it suggests that practices like meditation retreats with prolonged silence or darkness, while untested specifically for synesthesia, could in principle encourage cross-modal processing.
Why Bother? The Cognitive Perks of Synesthesia
Part of the interest in developing synesthesia comes from evidence that the trait confers cognitive advantages, particularly in memory. Synesthesia is linked to enhanced episodic and working memory performance.19PubMed. Synesthesia improves sensory memory, when perceptual awareness is high In one study, grapheme-color synesthetes maintained a memory advantage over non-synesthetes even after a full year, suggesting the benefit is durable and not just a short-term encoding trick.20Scientific Reports. A persistent memory advantage is specific to grapheme-colour synaesthesia
The memory advantage appears to extend beyond synesthesia-specific stimuli. Synesthetes showed a learning and retrieval advantage over older adults for associative memory tasks involving non-synesthesia-related material, suggesting that the perceptual mechanisms enhanced in synesthesia can translate into a broader cognitive benefit.21PubMed Central. Associative memory advantage in grapheme-color synesthetes compared to older, but not young adults Interestingly, whether the trained, pseudo-synesthetic associations produced by colored-reading exercises carry the same memory benefits has not been fully established, though the original Sussex training study did note improvements in IQ scores among participants.
Synesthesia and Artistic Involvement
Synesthesia has a long-standing association with creativity, and research bears this out, though with some nuance. Synesthetes show higher involvement in artistic activities and higher interest, ability, and self-reported performance across artistic domains compared to non-synesthetes.22The Journal of Creative Behavior. Synesthetes are More Involved in Art — Evidence From the Artistic Creativity Domains Compendium (ACDC) Artists are more prevalent among synesthetes, especially those with sound-color synesthesia, and synesthetes score higher on visuospatial abilities like mental rotation.23PubMed Central. Creativity and involvement in art in different types of synaesthesia
But the relationship between synesthesia and raw creative ability is more complicated. Only certain subtypes of synesthetes (specifically those with both grapheme-color and sound-color synesthesia) showed significantly higher divergent creativity compared to matched controls. Higher involvement in art does not automatically mean higher creative capacity. The researchers note that synesthetes’ affinity for art may be partly driven by their richer sensory experience making artistic activities more rewarding, rather than synesthesia directly boosting the cognitive machinery of creativity. For someone pursuing trained synesthetic associations, the practical implication is that the perceptual richness itself could make creative work more engaging, even if it does not automatically make you more creative.
When Heightened Sensory Connections Are Not Welcome
Not all cross-sensory sensitivity is pleasant. Misophonia, a condition in which specific sounds trigger intense emotional and physiological reactions, shares some underlying features with synesthesia in that it involves atypical sensory processing and cross-modal responses. Network analysis of misophonia symptoms has found that sensory sensitivity sits as a central hub connecting the condition to other traits including anxiety, obsessive-compulsive features, and heightened attention to detail.24PubMed Central / Wiley Online Library. A symptom network model of misophonia: From heightened sensory sensitivity to clinical comorbidity Synesthetes themselves sometimes report that their experiences can be overwhelming or distracting, particularly in noisy or visually complex environments.
This is worth considering before pursuing cross-sensory experiences with too much enthusiasm. The brain’s sensory boundaries exist in part to prevent overload. People with mirror-touch synesthesia, who feel physical sensations when they watch others being touched, sometimes find the experience distressing in medical or violent contexts. The goal of encouraging cross-sensory connections should include thinking about whether you actually want all sensory channels talking to each other all the time, or whether selective, controllable associations (like the kind produced by colored-reading training) are a more realistic and comfortable target.