‘Synaesthesia’ is a perceptual phenomenon in which stimulation of one sense organ leads to automatic, involuntary experiences in a second sense organ. Such associations can occur in any combination and in any number of senses.
There are various types of synaesthesia. The most common are:
In this type of synaesthesia, letters or numbers are perceived as inherently coloured. E.g., the letter ‘A’ may appear as red or the number ‘2’ as green.
In this type, numbers, months of the year, or days of the week elicit precise locations in space (for example, 1980 may be “farther away” than 1990), or may appear as a three-dimensional map (clockwise or counter clockwise).
Another common form of synaesthesia is the association of sounds with colours. For some, everyday sounds such as doors opening, cars honking, or people talking can trigger seeing colours. For others, colours are triggered when musical notes or keys are being played.
Spatial sequence synaesthesia
Those with spatial sequence synaesthesia (SSS) tend to see numerical sequences as points in space. For instance, 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 those without the condition
Other forms of synaesthesia include Auditory-tactile, (in which certain sounds can induce sensations in parts of the body), and Lexical-gustatory synaesthesia, in which certain tastes are experienced when hearing words. For example, the word basketball might taste like waffles.
Most synaesthetes become aware of their distinctive mode of perception in their childhood. Some have learned how to apply their ability in daily life and work. Synaesthetes have used their abilities in memorization of names and telephone numbers, mental arithmetic, and more complex creative activities like producing visual art, music, and theatre
Synaesthetes are more creative, in some ways, than other people. Many synaesthetes tend to excel at and spend more time engaged in art and music than other people. Musicians have talked about how synaesthesia actually helped them to learn music, and even be creative while composing. It helps them to develop perfect pitch because their ability to see/hear colours aids them in identifying notes or keys.
However, synaesthesia can also be disadvantageous. E.g., Driving while listening to music may be far more distracting than to someone who does not experience synaesthesia.
Sometimes, the condition also appears to be associated with some immune-linked disorders, including multiple sclerosis, irritable bowel syndrome, and some kinds of headache. Current reasoning on this matter is that both synaesthesia and these immune disorders are based on the same group of genes, but it’s not yet clear exactly how the two are related.