For some people, letter A always appears red even though it is printed in black; color red can has a smooth, milky "taste", and their favorite music "looks" like a big firework show... These people (perhaps 1 out of 2000 of us) who process a cross-sensory view of world are characterized as having the synesthesia
Some might think that synesthesia is an mental disorder, but in fact, most people with synesthesia are living normal lives. Because most kinds of synesthesia do not interfere with normal daily functioning, it is not classified as a form of mental diseases. In stead, synesthesia can sometimes introduce rather pleasant or "inspiring" experiences. Here is a picture demonstrating what a synaesthete sees when hearing the word "Saturday"
Synesthesia may become a source for inspirations. There are accounts from many musicians and artists which stated that their intermingled senses had help them greatly in producing creative ideas and artworks. And the statement of Nobel prize winner Richard Feynman reflects his synesthesia experience: "When I see equations, I see the letters in colours -- I don't know why. As I'm talking, I see vague pictures of Bessel functions from Jahnke and Emde's book, with light-tan j's, slightly violet-bluish n's, and dark brown x's flying around. And I wonder what the hell it must look like to the students." But whether and how the synesthesia experience might have affected Richard Feynman's achievement is not clear, other factors such as diligent work may have played more important roles in his achievements.
I am particularly interesting in the question of whether people with synesthesia can utilize their cross-sensory ability to enhance their cognitive and memory abilities. Synesthesia may give people extra "hooks" in minds on which to hang new information: for the grapheme-color synaesthetes, they can easily spot particular objects from their surroundings, such as number 2s mixed with a host of 5s because the 2s have different color than 5s. And as a grapheme synesthete says, "When I read, about five words around the exact one I'm reading are in color. It's also the only way I can spell. In elementary school I remember knowing how to spell the word 'priority' [with an "i" rather than an "e"] because ... an 'e' was out of place in that word because 'e's were yellow and didn't fit." By remembering particular letters in word have certain colors, grapheme-color synesthetes may have found a short-cut to master spelling tasks.
In much the same way, people with other kinds of synesthesia may have the potentials to become efficient learners under proper guidance and training.