Seeing things: tracks and chess
I've recently started a couple of games of online chess. I'm getting beaten badly. Basically I know just enough strategy to beat someone who knows little more than the rules. But people who know little more than the rules tend not to play chess.

But one thing that I've always been able to do is to clearly visualize the portions of the board attacked by a rook or queen. I can do knights as well, but only if I think about it. Knights have been my downfall in my recent games.

I don't think about the attacked squares systematically. I see them. The relevant portions of the board seem to sort of shimmer. It's an interesting cognitive effect. If I play around, I can get squares to shimmer differently, according to patterns that have nothing to do with the rules of chess.

What's really weird, though, is how strongly this shimmering reminds me of the shimmering of human or animal tracks, when I've been able to see them. I've tended to assume that the shimmering of tracks is due to an actual irregularity in the visual field. But the shimmering of attacked squares on the chessboard has no explanation other than that I know they are there.

I wonder if part (and if so, how much) of the ability to see tracks is simply knowing where they are supposed to be.