The idea is, I'm standing in the center of the circle swinging a toy on a string (the red circle) around in a circle. Bartleby is the black circle. Sometimes he would just run around the circle after the toy, but often he would anticipate where the toy was heading (sometimes well ahead of where it was) and dart straight across the circle by my legs to get it. He was pretty good at anticipating this and got it most of the time. In fact the times he chose to use this strategy and when he didn't probably had more to do with whether I was keeping it going at a constant speed than anything else.
But what is this solution called? Does anyone remember?