As a synesthete, anything about the ability of one sense to trigger another sense is immediately of interest to me. Gabe sent me this article from Wired, which also led me to this one from Discover. The point of both is that the parts of the brain we use to process input from each of our senses can be used to process information for other senses…basically just that the brain is extraordinarily plastic in ways that are almost impossible to conceive of because they challenge our fundamental perceptions.
(As a sidenote, we’re taught (in the US at least) that humans have five senses: sight, smell, taste, touch, and hearing. But in reality, we all have many more.)