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Hit Setup, Go then Throw Ball.

The catcher (arrow) has no prior knowledge of where the ball will fall, nor does he have the ability to calculate a trajectory. He only follows a simple rule: when the ball is high, fix gaze and maintain your position (forward or backward) so as to maintain that gaze angle.

See box insert in chapter 7 of Modeling Behavior in Complex Public Health Systems, by Christopher Keane. Dr. Keane based this model on an idea presented by Gerd Gigerenzer, in several of his publications. Gigerenzer uses ball catching as an example of simple heuristics that obviate the need for complex calculations, e.g. the ball catcher need not calculate a parabola. I wanted to test that heuristic with a model, and it turned out to be true. This is a good example of how small incremental adjustments with only local knowledge (gaze angle) can accomplish globally difficult problems (see chapter 7 in my book).