Linguistics; sensory perceptions and value judgments....
In the context of my recent attack of Blogger's Block I complained that my mind was "pudding -- vanilla pudding," and asked for questions, and badger wrote:
"How about flavor or taste sensory perceptions and value judgments, as in why is vanilla used as synonymous with bland, boring, dull, and mediocre?"

I think the reason "vanilla" (and often "plain vanilla") is used that way is because in cooking the most basic version of many recipes is the vanilla one, and then to make it fancy you have to add something.

This isn't fair to vanilla, which is a wonderful spice with a terrific fragrance; women used to dab it on their wrists or their throats in the same way that they did perfume. But I think the usage should be encouraged and nurtured, all the same, because it's one of the rare exceptions to the standard English practice of evaluating everything white as pure and good and positive and everything black as murky and evil and negative. We don't say that after you're "saved" you're "black as ebony," we say you're "white as snow." The good guys wear white hats (and have white wings); the bad guys wear black hats (and have black wings).

I think it's good for our English-speaking heads to have a common lexical item which is unambiguously white, and which is considered "bland, boring, dull, and mediocre."