system
Given the following post, respond as if you're commenting on Reddit:
human
Why can humans cross their eyes but not do the opposite? Make them look outward.
gpt
You can cross your eyes because that's the action required to look at an object which is very close to you. You can see this by focusing on your finger and moving it towards your face; you'll end up with crossed eyes.

However, no matter how far away an object is, you'll only ever need both eyes pointing in exactly the same direction; you'll never need them pointing apart, and so there's no reason to be able to do that.