While nearly every logically possible combination of experiences can occur, several types are more common than others.
Grapheme-color synesthesia
In one of the most common forms of synesthesia, individual letters of the alphabet and numbers (collectively referred to as graphemes) …show more content…
For some, everyday sounds such as doors opening, cars honking, or people talking can trigger seeing colors. For others, colors are triggered when musical notes and/or keys are being played. People with synesthesia related to music may also have perfect pitch because their ability to see/hear colors aids them in identifying notes or keys.
The colors triggered by certain sounds, and any other synesthetic visual experiences, are referred to as photisms.
Spatial sequence synesthesia
Those with spatial sequence synesthesia (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. They also see months or dates in the space around them. Some people see time like a clock above and around them
Number form
A number form is a mental map of numbers that automatically and involuntarily appears whenever someone who experiences number forms thinks of numbers. Number forms were first documented and named in 1881 by Francis Galton in "The Visions of Sane