Effect of electric toothbrush on Visual Perception

Eugene Leitl Eugene.Leitl at lrz.uni-muenchen.de
Mon Jun 3 09:47:46 EST 1996

On 1 Jun 1996, Robert Steven wrote:

> > [vibrato elettrico]
> How about this for an explanation/guess. You mention that you see the flicker
> when you look at the screen obliquely. This I believe is due to the fact that
> your peripheral vision is more sensitive to motion than your forward vision. The

This is correct. Lousy peripheral resolution but very good movement 
recognition. Evading unfriendlies, and such. Evolution artefacting 
generator process.

> computer screen is redrawn line by line at a certain "refresh rate". Below about
> 70 Hz your peripheral vision can detect the redrawing of the screen as a

It seems threshold varies from person to person.

> flicker. Above 70 Hz even your peripheral vision can't notice the redrawing of
> the screen. This is a good test when you're buying a computer monitor by the
> way, if it flickers when you look at it with your peripheral vision don't buy
> it - get a Macintosh.

Oh, come on. Flickering is a driver problem. Get a decent Linux box, and 
tweak xfree86 configs, and here you go -- both better resolution and 
higher fps than that of any Mac (their hardware is quite lousy). And dirt 
cheap in the bargain. MacOS loses when compared to Linux. Admittedly, 
Linux is also available for Mac (in this summer with a Mach microkernel 
with Linux personality), both Power and MC68xxx architectures.
> Anyway, what I think you've got is a monitor that has a refresh rate around 70
> Hz and you don't normally see any flicker when you view it with your peripheral
> vision. But when you vibrate your head with the toothbrush, it somehow affects
> your vision so that the flicker becomes noticable. I don't think it depends on

Retina wobbles back & forth, resulting in a strobo effect. Move your hand
rapidly in front of a bright CRT or make some saccades while looking at 
the CRT peripherally. Unless you work at c.a. 90 Hz fps, you should see 
lots of flicker.

> the frequency of the toothbrush vibration because I've noticed the same thing
> when I just click my teeth together while chewing food!
> -Rob
> steven at mshri.on.ca

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