Pretty interesting that the shape affects perception of flavor.
I always thought there were three shapes: http://hubski.com/pub?id=11032
I'm trying to imagine this, why it is the flavor that determines shape. I wonder if it could be that "smooth" and more mellow favors are active in a more localized area of our mouth's taste buds, vs acidly things which "spike" out further geographically on the tongue and in the mouth. Maybe Chinese egg roll mustard which lives almost past the tongue and up in the lower sinuses would be even more Kiki than the sharp cheddar because of its literal geography to some extent.
Interestingly enough (but omitted in the article), the cheeses were not judged based on "sharp" or "round" as explained, but on "kiki" or "bouba."
“How come the boot-shaped are so much more appealing than the oval-shaped ones?”
-It's all in the "dips". When the sweet and sour sauce is all but gone and there is only the bits in the corner left, the toe of the boot can get right up in there and use the remaining sauce. -C'mon, that's common knowledge, right?