None of the above! Synesthesia is simply a neurological trait allowing for communication between various areas of the brain that do not ordinarily exist. The vast majority of syntesthetes view their condition as a benefit and several studies have shown they tend to perform better on cognitive and intelligence tests. Synesthetes also test negative for psychosis, schizophrenia, and delusions.

In theory, there are as many subtypes of synesthesia as there are combinations of various sensations. However, given the many similarities and crossovers, many prefer to organize the subtypes into larger categories. You could, for instance, group synesthesia subtypes into the following broader categories:

• • • Language-color (words producing colors)
    • Language-taste (words producing tastes)
    • Language-touch (words producing physical touch)
    • Visualized sensations (visual perceptions of sound, pain and other non-visual sensations)
    • Sequence-space (perceiving ordinal sequences as occupying space)
    • Mirror-touch (experiencing the physical sensations of another person)
    • Tickertape (visualization of thought or spoken words)
    • Hearing-motion (perceiving sounds of silent moving objects)

You can see a far more aggregated list of synesthesia subtypes here.

There is currently no precise answer to this because we still do not even know exactly how many synesthetes there are in the world! There may be far more synesthetes who simply do not yet realize they experience the condition. Many synesthetes, I included, do not even realize that their perceptions of the world differ from others until later into their lives. Only further awareness and research will help us understand this for sure.

Though there is currently no conclusive proof that synesthesia is genetic or inherited, there is mounting evidence that it does run in families. Close to half of synesthetes report a first-degree relative also experiencing the condition. Research also suggests that synesthesia can skip generations, making it so that a synesthete may not have currently living relatives with the condition.

Not necessarily. Research throughout past decades seemed to indicate a predominance of female synesthetes. However, more recent studies have not corroborated this idea and show no bias among gender. A number of factors, such as females being more likely to self-report synesthetic experiences, may have originally helped encourage this notion.

While a formal statistic for the prevalence of synesthesia has not yet been conclusively agreed upon, leading research indicates the trait exists in only around 4% of the global population.

Research indicates that chromesthesia, or color induced by sounds, may be the most common form of synesthesia. However, other forms, like grapheme-color synesthesia (perceiving specific colors for alphanumeric characters or words) and experiencing days of the week and months in colors are also highly common among synesthetes. See more about the various types of synesthesia here.

While synesthetic experiences may be extremely vibrant and vivid, they are extremely different from experiences induced by hallucinogenic drugs. Like myself, many synesthetes do not even realize their experiences of the world are any different than others until much later in life simply because they are so ingrained in my perceptions. This is hardly the same as “tripping” or hallucinating.

*I personally have zero experience with hallucinogens of any kind and am basing my opinions on secondhand accounts.

There are essentially two primary methods for testing synesthesia. The first is through questionnaires, in which the likelihood and extent of the condition is assessed through targeted questions. This method is largely used for the sake of self-reporting.

The widely preferred method of testing is known as the synesthesia battery test. In this method, a battery of questions and visual responses are recorded and measured against a standardized scoring system, with the hopes of expediting and standardizing research on the condition. This test is free and available to the public and can be accessed here.

Many synesthetes — I included — deeply value their trait and would not give up their experiences for anything. However, not every one of the many forms of synesthesia are pleasant experiences and some are quite traumatic. Misophonia, for instance, produced unwanted emotions, like anger or fear, in response to certain sounds. Mirror-touch synesthesia, on the other hand, can cause one to physically experience the pain of another person.

Most synesthetic experiences occur within the “mind’s eye,” and therefore does not interfere with daily tasks or functions. For instance, in grapheme-color synesthesia, blue may be involuntarily triggered by the number 1 but is only perceived mentally versus physically on the page. In this sense, the synesthetic perceptions coexist with the real-life visual elements. However, though much rarer, there are also cases in which colors, shapes, sequences, and other associations are projected into the real world.

Currently, there is no evidence that synesthesia has any effect on an individual’s intelligence and causes no discernible difference from other members of society. A significant majority of synesthetes report not being able to imagine life without the condition.

Some studies have shown that synesthesia is upwards of three times more likely among individuals with autism, though this has certainly not been proven conclusively. While both conditions are believed to arise from increased neurological connectivity and communication, there is currently no formal link. Not to mention, most autistic people are not known to have synesthesia, and alternatively, the majority of synesthetes are not currently known to be autistic.

Synesthesia does seem to be more prevalent among individuals with artistic tendencies. Yet, there are many cases to the contrary, such as the Nobel Laureate physicist, Richard Feynman, who was a synesthete.

While the vibrant experiences of synesthesia naturally provide greater pathways for artistic influence and inspiration, it is not known to be the underlying cause of such talents.

Typically, synesthetes will disagree — and often enjoy passionately arguing — over the colors associated with characters. A significant portion of synesthesia research and testing has been developed to collecting the various perceived colors of synesthetes. However, some commonalities can be seen among large samples of experiences. For instance, it is common for the letter A to be perceived as red, B as blue, and C as yellow. Below is an image of the most commonly reported color associations for the English alphabet.

(Image Multisense Synaesthesia Research Lab)

Absolutely! It is quite common for synesthetes to experience multiple forms of synesthesia. This has been convincing evidence for a single underlying mechanism for synesthesia, versus each type being its own unique condition.

Yes and no. There have been cases of synesthetic experiences stemming from traumatic brain injuries and other traumatic events, though they are quite rare. Psychedelic drugs and hallucinogens, like LSD and psilocybin, are also known to induce synesthesia-like experiences. However, these experiences subside as the drug leaves the individual’s system. It is still widely believed that “true” synesthesia is innate and occurs from birth.

For the vast majority, the answer is no, synesthesia is innate and lifelong. Though more recent studies have indicated synesthetic experiences (in particular, color associations) may weaken with age. Other studies have shown experiences weakening dramatically or disappearing prior to adolescence.

Some studies have even suggested that everyone is born with the ability to intertwine senses but loses — or “grows out of” — the ability in the first few years of life. However, this is difficult to study since we cannot reliably ask infants about their synesthetic experiences. There have been other rare cases in which traumatic changes or injuries in the brain have resulted in the loss of synesthetic abilities.