Post by Al Johnston on Dec 20, 2005 18:04:55 GMT -4
There's a description of a related experiment in Daniel Dennett's Consciousness Explained, where a computer screen changes text while a person reads it (guided by a laser that shows where the eye is focussed). Essentially, the experiment demonstrates that the eye moves in jumps: muscles start and stop the motion, in between it is ballistic. And, while the eyeball is in motion, you don't actually see anything.
If our brains were simple enough for us to understand them, we'd be so simple we couldn't
Post by Joe Durnavich on Dec 20, 2005 18:26:47 GMT -4
Oh, yeah, I forgot about that one. Dennett says it is amazing to watch someone take that test because the text on the screen is changing like crazy, but the test subject doesn't see it because the word or words he is looking at at any given moment is not changing.
As I remember, though, if they display a word during the saccades the subject does see it, showing, even more unexpectedly, that we do perceive through the jumps of our eyes.
I was a volunteer in a uni students's psych experiment a few years ago which related to attention.
I forget the exact details, but it involved pressing a button as quick as possible each time I was given a mild electric shock. When I was concentrating on another task (riding an exercise bike at a very precise speed) my response time increased considerably.
Post by Joe Durnavich on Dec 20, 2005 20:15:55 GMT -4
I wrote Oh, yeah, I forgot about that one. Dennett says...
Heh. Perhaps somebody should give me a mild shock when I start out saying I forgot about something and then go on to describe it. Al has it right. The computer would predict where your eyes will fall at the end of a saccade (because your eyes are on a ballistic trajectory), and it would change the word at that spot with one of the same length. You wouldn't see the change. However, if they displayed a word that tracked along your eye movement during the saccade, you would see that.
This is a good example of me being a typical eyewitness filling in gaps in my memory. I read this book, and I remembered the part about the text changing and the part about seeing words that track your eye movements, but I couldn't remember exactly what text changed and when. In looking back on this, I see that I "reasoned out" that they must have been changing all the text outside the foveal area, when in fact, that text (except the one word) remained unchanged.