system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5 How do hidden object optical illusion pictures work?

My mom has a picture in her room with a crazy optical illusion design. Everybody says they see a picture of Jesus on the cross but I've never seen it in 25 years. I've never been able to see any objects in those hidden object pictures. I think everyone who says they can see those are full of it.
gpt
Nah, it's a real thing.  


Basically you're unfocusing or crossing your eyes so that the repeating parts of the pattern on the image overlap one another.  
Hit the sweet-spot, and there are subtle differences in the pattern which produce an image when brought together.  


If you want to train yourself, get two similarly sized/shaped objects on a plain background and try and cross your eyes so there appear to be three of them.  


If you can do that, you'll be able to see jesus.