Synesthesia is a condition experienced by approximately 1 in 200 people, in which one sensory experience (say, seeing the letters of the alphabet) consistently evokes another sensory experience whose source is not in the external environment, but in the person's mind. For example, a person may see each letter of the alphabet in a distinct color (even though the ink on the page is all black), or each musical note heard on the scale might be accompanied by a particular taste. Generally these relationships are consistent, i.e..'a' is always light blue and 'b' brick red. For a long time, scientists doubted the veracity of these reports, thinking that the synesthetes simply had strong imaginations so that they felt as though they saw blue, or were people with a psychological makeup such that they wanted attention for having an unusual skill, but it has since been shown that this experience has all the verisimilitude of a perception of external stimuli, despite the fact that the synesthete's brain is producing the accompanying experience. V. S. Ramachandran explains how this was tested in his book A Brief Tour of Human Consciousness.
Experiments indicated that he had no difficulty reproducing any lengthy series of words whatever, even though these had originally been presented to him a week, a month, a year, or even many years earlier. In fact, some of these experiments designed to test his retention were performed (without his being given any warning) fifteen or sixteen years after the session in which he had originally recalled the words.Not only that, he could produced them backwards.
I recognize a words not only by the images it evokes but by a while complex of feelings that image arouses.However, what S. failed to encode was the associations among the elements of his memory traces that were related by logic given their meaning. So the very techniques that gave S. his prodigious memory compromised his ability to capture the gist of of what he was remembering. In fact, S. often struck those he met as disorganized and not terribly bright, as impressive as were his memory talents. Indeed, these multiple sensation called up by each and very sensory experience were an impediment to much of his everyday functioning.
When I ride in a trolley I can feel the clanging it makes in my teeth. So one time I went to buy some ice cream, thinking I'd sit there and eat it and not have this clanging. I walked over to the vendor and asked her what kind of ice cream she had. "Fruit ice cream," she said. But she answered in such a tone that a whole pile of coals, of black cinders, came bursting out of her mouth, and I couldn't bring myself to buy any ice cream after she'd answered that way...People in my field, particularly in its inception, often learned about normal brain function from atypical brains. Although the writing is a bit repetitive, Luria's portrait is a brief, vivid, and humane introduction to neuropsychological case studies for anyone interested in getting an introduction to such writing.