Realism

First off, why are they called "trailers" if they precede both the feature and the movie they advertise? Seriously, I'd like to know. The OED is unhelpful.

Anyhow, sitting in Panera today, reading The Emperor's Children, I found myself thinking about literary realism, which we all know is a total social construction and bears no actual relation to "reality," whatever that might be, and a heinous bourgeois convention to boot, more insidious and proletariat-oppressing than paying $3.66 for a cup of chicken noodle soup and a hunk of bread just because the walls are painted burnt sienna and there's free wi-fi. Blah, blah, blah.

Here's the thing, the above thesis is, in certain respects at least, empirically testable. Take, for example, the way authors set a scene, typically describing the environment and then moving on to different aspects of the persons within the environment, establishing first of all major physical traits of the characters, such as sex, age, ethnicity, rough build and height. Now, these are, I think, the traits that humans tend to be able to identify in others most quickly given extremely limited visual exposure. If one were to sample a large number of character introductions, quantify the priority of different features attributed to the characters, and compare these with the characteristics identified by people in the real world, that would constitute empirical evidence that literary realism was more than conventional.