This is one of the most common types of synesthesia. A person who experiences this may associate/see individual letters or numbers with a specific color. Usually, two people won’t report the same color for letters and numbers. However, studies have shown that many synesthetes will see some letters the same way (for example, ‘A‘ is likely to be red).

 

 

 

 

 

A number form is essentially a mental map that consists of numbers. When a person with number-form synesthesia thinks about numbers, a number map is involuntarily visualized. It is sometimes suggested that the number forms are a product of “cross-activation” between regions in the parietal lobe – a part of the brain that is involved in numerical and spatial cognition.

 

 

 

 

 

 

This type is known as ordinal-linguistic personification, or OLP. An individual who experiences this will associate ordered sequences with various personalities. Ordered sequences may include numbers, letters, months and so on. For example, a person with OLP may look at the letter ‘A’ and think in his mind that ‘A’ is a rude letter.

 

 

 

 

 

When sound triggers the visualization of colored, generic shapes, sound-to-color synesthesia is at play. For certain people, the stimuli are limited, and only a few types of sounds will trigger a perception. However, there are cases wherein many different sounds trigger color visualizations. Usually, the perceived colors appear in generic shapes – squares, circles, etc.

 

 

 

 

 

 

Lexical-gustatory synesthesia is one of the more rare synesthesia types. Synesthetes who experience this kind of synesthesia evoke different kinds of tastes when they hear certain words or phonemes. According to research, associations between the words and what a synesthete is able taste are constrained by tastes he or she has experienced early in life. So, if an individual hasn’t had mashed potatoes or bacon, they won’t be tasting those flavors as a result of this variation.