Dominant Eye


Have you ever taken the dominant eye test? Apparently it consists of holding your arm straight out, and covering up a distant object with your thumb. Then you close your eyes one at a time, and see which eye makes the thumb move. The other eye is then your dominant eye.

I think I first heard about this test in high school, but it doesn’t work for me. Every time it comes up, I try it, and I get frustrated, and other people get frustrated trying to explain it to me.

When I hold my thumb out at arm’s length, and look at distant objects, I do not see one thumb, I see two. Both are transparent. neither of which can actually be said to “cover” that object. I can cover it with my whole hand, my hand’s large enough that I get a significant overlap between the two hand images that I see.

Conversely, I can look at my thumb, instead of the distant object. Then I only see one thumb, but see two distant objects. I can cover either one of those up with my thumb, but the other is still out bright and clear.

I looked up other tests for finding the dominant eye. One consists of holding your hands out together, thumbs out, overlapping and leaving a hole between your thumbs and forefingers, then centering the distant object in the hole. Once again, I see two holes. I can look at the object through either hole, but to center it, I’d actually put it behind the fleshy bridge between the holes.

I don’t know if I just don’t have a dominant eye, or something else weird is going on. But for between 20 and 30 years, I’ve been trying to do this, and have only gotten frustrated. I don’t know why it works for other people, if their mind suppresses the image of one of the thumbs, or what.