Synesthesia is a neurological condition that an individual experience which allows her or him to perceive stimuli using a sense that is normally not associated with the stimuli. For example, people with chromesthesia, a type of synesthesia, can hear sounds when a color comes up – for example, hearing a trumpet when they see a red apple. There are various other types of synesthesia, such as seeing alphabets and at the same time seeing colors associated to them or hearing words and feeling a skin sensation with each different words said.
Since these experiences are unique to the individual who has the condition, Cytowic’s friend should come up with a demonstration so that Cytowic can experience the same thing he does.