What color is Tuesday? Exploring synesthesia

How does one experience synesthesia -- the neurological trait that combines two or more senses? Synesthetes may taste the number 9 or attach a color to each day of the week. Richard E. Cytowic explains the fascinating world of entangled senses and why we may all have just a touch of synesthesia. [Directed by TED-Ed, narrated by Richard E. Cytowic].