Correct!

Now your eye is pointing forward again, in the same direction as it was when it started.

But notice where the dark side is now compared to where it was at first.

Before the dark side was on the bottom. Compared to before, the eye is on its side. It has violated Donders' law.

If you try the same three rotations again the eye will end up upside down in the head. This is can be painful!

Granted, these are big rotations and normally the eye cannot turn by much more than 45 deg. from center

But since the eye makes saccades a few times each second, a bad choice of axis can quickly lead to this problem even when the saccades are small.


Copyright © 1996 Tutis Vilis and Douglas Tweed
University of Western Ontario
London Ontario Canada
Updated October 28, 2005

Comments welcome. Email to tutis.vilis@schulich.uwo.ca