Why can you cross your eyes to the center, but not to the sides?

Question

Why can you cross your eyes to the center, but not to the sides?

Answer 1

Human binocular vision is arranged such that both eyes will always try to focus on the same point or location.

When the point that you try to focus on is very close to your own face and near the center - like the tip of your nose, for example, your eyes become "crossed" when both eyes look toward that point.

You cannot "cross" your eyes to the sides because that would mean that your two eyes would be looking at two different points in space, which is simply not what they are programmed to do.