The well-known American ethnologist Alfred Louis Kroeber made a rich and in-depth study of women's evening dress in the West, stretching back about three centuries and using reproductions of engravings. Having adjusted the dimensions of these plates due to their diverse origins, he was able to analyse the constant elements in fashion features and to come up with a study that was neither intuitive nor approximate, but precise, mathematical and statistical. He reduced women's clothing to a certain number of features: length and size of the skirt, size and depth of the neckline, height of the waistline. He demonstrated unambiguously that fashion is a profoundly regular phenomenon which is not located at the level of annual variations but on the scale of history. For practically 300 years, women's dress was subject to a very precise periodic cycle: forms reach the furthest point in their variations every fifty years. If, at any one moment, skirts are at their longest, fifty years later they will be at their shortest; thus skirts become long again fifty years after being short and a hundred years after being long.

It's often said that those who can't do, teach. It would be more accurate to say that those who can do, can't teach the basics. A great deal of expert knowledge is implicit, not explicit. The further you progress toward mastery, the less conscious awareness you often have of the fundamentals . Experiments show that skilled golfers and wine aficionados have a hard time describing their putting and tasting techniques — even asking them to explain their approaches is enough to interfere with their performance, so they often stay on autopilot. When I first saw an elite diver do four and a half somersaults, I asked how he managed to spin so fast. His answer: "Just go up in a ball." Experts often have an intuitive understanding of a route, but they struggle to clearly express all the steps to take. Their brain dump is partially filled with garbage.