Synesthesia is a cross over of senses. People with this condition have experiences where one sense, say hearing is simultaneously perceived with another sense such as sight.
I decided to write on this topic because I heard about it in an episode of Criminal Minds, where a criminal was experiencing visual and auditory sensations simultaneously. As people spoke to him, whether it was in person or over the phone he could physically see the words and they would appear in different colors. The next day I came to school, and in my Anomalous Experience Class our Professor was lecturing on this absolutely fascinating topic.
We are all on a continuum experiencing some level of Synesthesia. Some people experience stronger levels. For example, sometimes we link certain colors with human feelings or emotions. In my Anomalous Experiences class, Professor asked us which one has no friends? Our options were a yellow circle or a blue circle, both the same size. The majority of the class voted that the blue circle had no friends. Meaning we on some level thought that yellow, was a happier, friendlier color than blue. Crazy? Or not?
Some known causes...
1. Developmental: people are born this way.
2. Trained: association created by repeated pairings
3. Transient: posthpnotic suggestion, psychotropic drugs, sensory deprivation
4. Adventitous: brain injury or disease (blindness)