A reader writes (thanks nick!)
Not gonna impress any girls with this one, but… I was looking at my mother’s ceiling fan the other day trying to determine how many blades it had. It was on its highest setting so it was nearly impossible to do. Until I blinked. If you blink rapidly, it disrupts the brains attempts at connecting frames of sight into continuous motion. Thus a whirling blur becomes a clear frame of sight, easily analyzed. Not sure where else this little trick could pay off. A nice illustration of the characteristics of our visual systems though.
Cool. Freed from the constraint having to make sense of continous input, your visual system can to make sense of the single ‘frame’ of input it does have. An example of less is more? I noticed something similar when riding my bike. When I glance down at the front wheel, it appears blurred. But when I look back at the road, my visual system delivers me a snapshot of the wheel, unblurred. What is happening – I’m guessing – is that as I move from looking at the wheel to the road ahead there is a moment of saccadic suppression [Hack #17] when visual input is cut off. Into this gap the ‘frame’ of the wheel is resolved. Also lending a hand may be a neural mechanism which turns off saccadic suppression if the velocity of the eyes matches that of a moving object (with your eyes stationary a moving object is blurred, with your eyes moving a stationary object is blurred, but if your eyes move at the same speed as an object you can get a clear image). For this to work the object needs to be nicely textured, so your low-level visual apparatus can gauge its velocity. Which explains why i get the effect on my mountain bike, which has big treads on the tyres, but not on a road bike, which has smooth tyres.