Synesthesia refers to a specialized phenomenon in which stimulation <en.wikipedia.org/wiki/Stimulation> in one sensory or cognitive modality leads to automatic, involuntary occurrences in another sensory or cognitive modality. Many synesthetes undergo two or more crossmodal correspondences, and others with unusual cross-modal sensory undergo non-sensory correspondence. Synesthesia is an active research area because of its uncomprehensive nature. Many synesthetes have a gift <www.britannica.com/topic/the-arts>of arts, increased memory skills, and a great sense of creativity <www.britannica.com/topic/creativity> <www.britannica.com/science/memory-psychology>.
As a general rule, synesthesia can occur in any sequence of sense or cognitive pathways. The most common form of synesthesia is grapheme-color. Graphemes (letters or numbers) takes on specific colors to the synesthete. For example, a synesthesia person could still see the letter B as blue, but that doesn’t imply that all synesthetes will experience the same color. Another common form of synesthesia is sound-to-color synesthesia. This kind of synesthesia could mean a few different things like a noise from a car horn or sound from a cow takes shape or color in the mind when it is heard. One might experience specific sound as a texture, and others can “see” music and incorporate different types of musical notes with colors of the rainbow <science.howstuffworks.com/nature/climate-weather/storms/rainbow.htm>. An interesting study in 2006 showed that sound to color synesthetes connected a higher pitch to a lighter color. This led to researchers’ conclusion that synesthesia could be using a crossmodal pathway used by most people and not any paths unique to the condition. The next form of synesthesia, which is a rare type, is lexical-gustatory or olfactory. These kinds of synesthesia could take a meal or any flavor based on a word, a visual picture, or a sound. They might also associate a smell with a specific shape or color, and others claim to taste other people’s emotions <science.howstuffworks.com/life/what-are-emotions.htm> <www.npr.org/blogs/thesalt/2013/03/12/174132392/synesthetes-really-can-taste-the-rainbow>. Another type of synesthesia which is not common is mirror-touch synesthesia; this makes people experience a physical feeling when other people are touched. Ordinal-linguistic personification is a condition where people could give personality traits to different objects or items in ordinal lists. For example, saying letter A appears brave, the letter B egotistical and letter C nurturing; it can also happen in days, weeks, numbers, and so on. Number-form involves people seeing numbers as a very distinct map. The commonly seen lower numbers are bunched at one end. They might not appear linear, but they might curve up and down or move up and down.
Different regions in the brain are specialized for specific functions. An Increase in cross-talk between areas specialized for various functions may reveal reasons for the many types of synesthesia. The majority of people with synesthesia are generally born with it, or it develop <www.ncbi.nlm.nih.gov/pmc/articles/PMC3797969/>s in childhood. Research suggests that synesthesia can be genetically inherited. <www.ncbi.nlm.nih.gov/pmc/articles/PMC3222625/#pbio.1001205-Simner1>Each of the five senses stimulates a different region of the brain. For instance, the primary visual cortex at the rear of the brain will be light up by a bright white wall. The bright white wall also stimulates the parietal lobe, which is responsible for telling a person how something tastes like. So if you have synesthesia when you look at the wall, you feel like you can also taste it. This is the reason researchers believe that people who have synesthesia have a higher level of interconnection between different parts of the brain that are joined together by sensory stimuli. Some substances can cause temporary synesthesia. The use of psychedelic drugs can intensify and connect your sensory experiences. Psilocybin, <www.healthline.com/health/how-long-does-acid-last>cannabis, LSD, mescaline, and alcohol have been s <www.ncbi.nlm.nih.gov/pmc/articles/PMC3797969/>tudied for their capacity to cause temporary synesthesia.
Cytowic, Richard E. *Synesthesia: A union of the senses*. MIT Press, 2002.