Thank you for your responses. I, unfortunately, gave my student a variant
of the answer below. I had everyone jiggle their eyes with their hands in
class. And, I must admit to feeling pretty good about it. I also
hypothesized that if that were the case then other objects with similar
spatial frequency would also appear to jiggle. Well....
last monday my student brought her electric toothbrush, her electric
clock, and a package with writing of about the same contrast and spatial
frequency to the class and challenged me and other students to try it.
Only the clock digits appeared to jiggle. (We spend a few minutes before
each class talking about current affairs and applications of material etc.
So, it was fun.)
Was my experiment misconceived or is the answer wrong?
Thanks!
--------------
Not being an electric toothbrush user, this is a guess, but an educated
one. Motion of the eye that is produced via the normal eye control system
(including head movements, etc) are interpreted as eye moving, and world
stationary. Movement of the eyes produced through other channels
((pushing
on the eye (through the lid) with the finger, etc) is interpreted as
produced by movement of the world. v. Holst has a theory to explain this
(reafferent information results from self produced motion , whereas
exafferent information is from movement of the world) in feedback terms.
The arm-toothbrush is not part of the buuilt in feedback mechanism.
The same principle explains why you cant tickle yourself.
don
Donald McBurney
Faith L Florer wrote:
> Does anyone here know why it is that the numbers on a digital clock (and
> some images on a television screen) appear to jiggle when a person is
> using an electric toothbrush?
>
> I was asked this question in cognition class.
>
> Thank you.
>
> Faith Florer
>
> Faith Florer, Ph.D., Adjunct Asst. Professor Marymount College and NYU.
> http://www.river.org/~flf/Faith.html
