An experiment to determine how much your Listing's plane turns when you converge.

1. After you click on next, you will see two images.
2. Center your head 1 to 2 ft from screen (the closer the better)
3. Cross your eyes so that you see them singly.
4. The two horizontal lines should appear parallel. If they are not try to center your head better.
5. Now tilt your head up slowly. You should see that the lines no longer appear parallel.
6. If you tilt you head down slowly, the lines should tilt in the opposite direction.
7. Remember how the lines were oriented when your head was tilted down (i.e. when your eyes were looking up).