ORIGINAL: Rebel Hog

One test that has been purported to show "eye dominance" is as follows:

1) With both eyes open, look at an object in the distance.
2) Raise a finger and line it up so that your finger is overlapping the
object.
3) Now close one eye. If it looks like your finger "jumped" (it is no
longer lined up with the object), then the eye you closed is "dominant."

This test works because your two eyes have a slightly different
perspective, and the "dominant" eye was used to line up your finger.