You know when you are sitting there silently and then suddenly (this all happens in an instant!) your head turns because you thought you saw something move? Perhaps it was a shadow that played across the floor or an artifact of the wind (though your mind uneasily suspects it may be a mouse scurrying for cover.) Thats been happening a lot to me recently and nothing is ever there. Still, I am compelled to look each time.

This little visual trick fascinated me as a kid. It seemed to come from deeper inside me, beyond volition, that instinct to turn and look. Are the shadows real that I see or were they too deceptions of my mind? How could I say i was in control of myself if I could not understand my own mind?

Equally impressive to me was that capability we have (the solution must be immense and devious) of picking out such tiny movements in such a large visual field. Years later, I got so much enjoyment of the method that astronomers use to find comets or other moving objects in a large starfield. Not with computation of course but by flashing two overlayed images (like an animated gif) and letting our magnificent eye hone in on the moving target. An old slide projector will do the trick too.