Do you subconsciously assign personalities or genders to numbers or letters? Are 5 and 6 different colors? If so, you may be part of the 3.7% of the general public that has some type of synesthesia. Synesthesia is the neurological phenomenon where two or more of your senses are unexpectedly connected. For example, you might not only see the color blue, but you can also hear it, taste it, or even smell it. There are at least 77 different types of synesthesia, some of the more common types being grapheme-color synesthesia, chromesthesia, spatial sequence synesthesia, and ordinal-linguistic personification. There are other less common types, such as lexical-gustatory synesthesia, which accounts for about 0.2% of the general population.

Grapheme-color synesthesia is characterized by associating numbers and/or letters with colors. It is the most common type of synesthesia. The number 5 might be green, and the number 2 might be pink. If shown a set of 5’s with one 2 hidden, a person with grapheme-color synesthesia would be able to instantly differentiate between the numbers without difficulty. About 59% of synesthetes have this type, often coinciding with at least one other type. The specific colors of each letter or number are not universal, and putting two synesthetes together will likely lead to an argument over what color “e” is. There are some consistencies, though, such as the letter “a” being red most often.

Chromesthesia is similar to grapheme-color synesthesia, but instead of numbers or letters being associated with colors, it involves sounds.  It is less common than grapheme-color, occurring in about 15.6% of synesthetes. Many musicians have this type of synesthesia, notable ones being Kanye West, Pharrell, Billy Joel, Jimi Hendrix, and Mozart. The colors that they see influence the music they produce, and most see chromesthesia as a gift. The color associations are unique for each person, but in most cases, consistent over time. Chromesthetes have unique color pairings. However, all studies have reported that synesthetes and non-synesthetes alike match high pitched sounds to lighter or brighter colors and low pitched sounds to darker tones, indicating that there may be some common mechanism that determines the associations present in typical brains.

Those with spatial sequence synesthesia (SSS) tend to see numerical sequences as points in space, or as a number form. A number form is a mental map of numbers that automatically and involuntarily appears whenever someone who experiences it thinks of numbers. For example, the number 1 might be farther away and the number 2 might be closer. People with SSS may have superior memories. In one study, they were able to recall past events and memories far better and in far greater detail than the control group. They also see months or dates in the space around them. Some people see time like a clock above and around them.  Number forms were first documented and named in 1881 by Francis Galton in “The Visions of Sane Persons.”

Ordinal-linguistic personification (grapheme personification) is a form of synesthesia in which ordered sequences, such as ordinal numbers, weekday names, months and alphabetical letters are associated with personalities and/or genders. Although this form of synesthesia was documented as early as the 1890s, researchers have, until recently, paid little attention to this form. Similar to OLP is time units → color synesthesia (the arrow represents the relationship between the trigger, time units, and the response, perceiving a color). This is when time units, such as weekdays, months, or seasons have colors associated with them. For example, Sunday could be maroon, Monday black, Tuesday grey, Wednesday green, Thursday navy blue, Friday light blue, and Saturday pink. These colors are subconsciously assigned to the time units, which is different from an ordinary person picking colors they like and purposely associating them with days or months. About 22.5% of synesthetes have some form of OLP or time units → color synesthesia.

Lexical-gustatory synesthesia is a rare form of synesthesia where spoken and written language (as well as some colors and emotions) causes individuals to experience an automatic and highly consistent taste/smell. The taste is often experienced as a complex mixture of both temperature and texture. For example, in a particular synesthete, the word jail might taste of cold, hard bacon. Synesthetic tastes are evoked by an inducer/concurrent complex. The inducer is the stimulus that activates the sensation and the taste experience is the concurrent. The documentary ‘Derek tastes like earwax’ gets its name from this phenomenon, in references to pub owner James Wannerton who experiences this particular sensation whenever he hears the name spoken. An estimated 0.2% of the population experiences this form of synesthesia, making it one of the most rare types.

There are extensive lists of all the currently known types of synesthesia, and these five are just some of the more common/well-known types. At this time, there are at least 80 different types. Links to some websites that contain more information on these are below. Synesthesia is a fascinating phenomenon that is definitely worth reading about, especially if any of these descriptions resonate with you. There are many people who might have some form but do not realize what it is or assume it’s something everyone experiences. Being a synesthete is something to be proud of, and most see it as an added bonus to their life.

Links about synesthesia:

http://synesthete.org/index.php – an interesting website that contains an extensive test to measure levels of possible synesthesia as well as general information

http://www.daysyn.com/Types-of-Syn.html – a website that lists all currently known types of synesthesia and is regularly updated

http://www.apa.org/monitor/mar01/synesthesia.aspx – includes data from scientific studies

https://en.wikipedia.org/wiki/Synesthesia – the wikipedia article about synesthesia, it has tons of information and links to multiple in-depth articles about specific types and examples