Tuesday, 2024-03-19, 7:58 AM

Welcome Guest | RSS

YOUR SEARCH ENDS HERE

THE BEST ENTERTAINMENT SITE

<<LAST               <<------->>               NEXT>>

  Sigma Motion 

Content on this page requires a newer version of Adobe Flash Player.

Get Adobe Flash player

Warning: this may take practice to see, but I feel it’s worth it.

The image above should (hopefully) flicker wildly. Now move your finger along it from left to right, with a speed such that you travel the distance in about 3 seconds, while following the finger with your gaze. When you hit the right speed, you should perceive a smooth rightwards motion of the stripes. Now move your finger back. If you follow it again with your eyes, you will see smooth leftwards motion of the stripes! After a little practice, you can voluntarily switch movement direction without your finger as a guiding target.

While you perceive the illusory motion, your eyes do a smooth pursuit with occasional backwards saccades, also known as oculokinetic nystagmus.

Comment.

The stimulus is just a rapid phase reversal (at 30 rev/s) of a bar pattern. The occasional jerks are due to aliasing of the reversal frequency by the raster frequency of your display and would not occur if I could synchronize to your screen build-up.

This phenomenon was named "Sigma Motion” by O. J. Grüsser, but first reported by James Pomerantz. It demonstrates the interaction of image reversal and eye movements, with efference copy at work.

Sources

Behrens F, Grüsser OJ (1979) Smooth pursuit eye movements and optokinetic nystagmus elicited by intermittently illuminated stationary patterns. Exp Brain Res 37:317–336

Pomerantz JR (1970) Eye movements affect the perception of apparent (beta) movement. Psychonomic Science 19:193–194

DISCLAIMER:

CONTENTS ON THIS SITE DEPENDS ON FRAMING SITES.

I HAVE DESIGNED THIS SITE BY FRAMING ALL THE BEST SITES  AVAILABLE IN THE web...

please leave your comments here

or

contact me at 

nikhilr89@gmail.com

Views: 27661 | Added by: nikhilr | Date: 2010-07-26 | Comments (32)