Fascinating saccade-tracking document at this Wikipedia article. Here’s more on general scanning of photos.
And check out this article too, indicating that when we read, we can only see 4 or 5 letters at a time with high acuity.
Eye tracking – saccade recording
- Post author:Erich Vieth
- Post published:December 30, 2013
- Post category:Psychology Cognition
- Post comments:2 Comments
Erich Vieth
Erich Vieth is an attorney focusing on civil rights (including First Amendment), consumer law litigation and appellate practice. At this website often writes about censorship, corporate news media corruption and cognitive science. He is also a working musician, artist and a writer, having founded Dangerous Intersection in 2006. Erich lives in St. Louis, Missouri with his two daughters.
I don’t have a reference for this, but years ago I read an interesting study about eye movement. A little-known aspect of vision is that, in addition to tracking from point-to-point in the visual field, the eye actually does not stare fixedly at any given point. When you look at a fixed point, your eyeball will actually jitter a tiny bit, back and forth, involuntarily. This jitter keeps the image on your retina in continual motion, which keeps the image moving over the rods and cones. Without this movement, the nerves in the retina would fatigue and stop firing, with the surprising result that they would stop sending signals to the brain — and the point you are looking at would become invisible. The study I read about involved an experiment where subjects were asked to look at a picture on a CRT screen. Cameras were pointed at the subject’s eyes to record their eye jitter, and then a circuit would jitter the picture on the screen to compensate (i.e., nullify) the subject’s eye movement. In a matter of just a few seconds, the subjects were unable to see the picture, even though it was still on the screen. Some people can mimic this result by staring hard at a fixed point and, to some extent, consciously overriding their autonomic eye jitter. Try it for yourself. Stare at a fixed point and see if, after a few seconds, you become unable to see the thing you are staring at.
Grumpy: In the early days of Lasik, the laser was not nearly as good at tracking as it is now. Before I had the procedure back in 1999, I practiced staring at a dot on the ceiling for 3 minutes. It was an eternity and it was difficult. And yes, the dot tended to disappear when I was doing it right.