Synesthesia is a rare and remarkable phenomenon. It is when two senses intertwine and accompany eachother. Think of it this way: There are separate paths in your brain for each sense. Synesthesia is when two or more senses mix, and cross each others paths. There are several different forms of synesthesia. For example some people with synesthesia can see sound, hear tastes, or hear motion. One of the most common types of synesthesia involves letters and colors. When they look at letters are numbers, they have a certain color associated with it.
I have synesthesia myself, and didn’t even realize it until a few years ago. I have motion —> sound synesthesia. That means that when I see something move, I can hear a sound that goes along with it. I have had it my whole life, and didn’t even know what it was called until only a couple years ago! I was sitting at a park with a few friends when I saw a sign flashing. There was a horrible noise that went along with the flashing, and I asked my friends if they could hear it. They all said they couldn’t. I did some more research and found out I had it!
Now, some people have severe synesthesia that actually affects their everyday life. For example, when I see something move and hear the sound that goes along with it, it isn’t very loud at all. It is a faint noise, and I can easily ignore it. People with a more severe type would hear a very loud sound that would affect their lives.
Now nobody knows exactly how synesthesia forms, but there are a few theories. The theory I mentioned above where I said the different paths in the brain crossed is called the Neuronal Theory. This is the theory I believe in, but there are a few others who would disagree. There is also the Degeneracy Theory that states synesthesia is a sign of repression, like that is found in schizophrenia. There are a few other theories including the Vibration Theory, Emotional Theory, The Compensation Theory, etc.
Anyway, those are the basics of synesthesia including some personal experience I have had with it. Scientists are learning more and more about it everyday. It is a very interesting phenomenon, and I would recommend all of you go and research some more about it! There are several books you can read including The Hidden Sense: Synesthesia in Art and Science by Cretien van Campen. I also recommend Blue Cats and Chartreuse Kittens: How Synesthetes Color Their Worlds by Patricia Lynne Duffy.