A fascinating article: What We See When We Read
A thought experiment: Picture your mother. Now picture your favorite literary character. (Or: Picture your home. Then picture Howards End.) The difference between your mother’s afterimage and that of a literary character you love is that the more you concentrate, the more your mother might come into focus. A character will not reveal herself so easily. (The closer you look, the farther away she gets.)
This whole article is well worth reading.
It’s also interesting to me because I do relatively little — sometimes almost no — physical description of characters. I have literally written entire books without ever describing the protagonist. That has occasionally caused a few minutes of bother, as an editor will sometimes ask, “Who’s an actor who looks sort of like your protagonist?” and I have no idea (a) of the names of any actors of remotely the right age and general type; and (b) only a vague idea what my protagonist looks like. I have to sit down and google “young male actors” or whatever and scan through a lot of images until I finally say, “Sort of like Really Famous Person I Had Never Previously Heard Of.”
In some ways I have a very visual imagination. But not in that way.
By all means click through and consider the question of what Anna Karenina looks like.