As a kid, I got a Magic Eye book and learned to see it by crossing my eyes (ie, focusing in front of the screen). I thought it was pretty interesting when I realized that I was seeing all the images inverted ("peaks" were "valleys" and vice versa) due to the way I was focusing. Alas, I never was able to see the images "correctly".

Yup, I loved Magic Eyes as a kid. This was easy.

Nevertheless, I was astonished that "impossible mode" literally took me only 1-2 seconds to find the missing star.

Like, I knew our vision is good at interpreting depth from images. I figured it would be all right at finding large areas of differences. I had no idea a single freaking pixel could stand out like a sore thumb.

Maybe we are the opposite. As a kid, I could only do cross-eyed-focus-in-front-of-screen, but not "focus beyond the screen". Or a book at the time.

So I was able to see the 3D in Magic Eyes, but the 3D effect was inverted.

Today as an adult I am able to focus beyond the screen, but it's still much easier for me to do it cross-eyed.

I also got all the images in the post almost right away. But my eyeballs focused in front instead > _ <

I have a slightly lazy right eye, so this has always come naturally to me, but I will say it's considerably easier to achieve the false focal lock on printed material— something about screens, even quality ones with high refresh rates, just isn't the same.

How do you do this focusing beyond the screen!?

I'm trying so hard to make this happen. Stare really far in the distance and then move the image in front of my face on my phone. No matter the distance between my face and my phone i can't overlap the images.

Focus in front of the screen is the easy one. How do you get beyond....

I'm great at magic eyes / stereograms and have a ton of posters around my house with them, but I still had trouble with seeing the differences in the test images. I easily locked in my focus on the overlapping cat images but only one difference stood out to me. I eventually got them all but it wasn't that easy (maybe with practice I could get there). The differences are noticeable when I focus right on it, but when I'm looking at the whole image it's harder to tell what is missing from one eye.

I can get the images to merge but the differences don't stand out.

I can do magic eyes, but this technique doesn't work for me. My left eye is dominant enough that the whole image just looks like what my left eye is seeing.

I’ve done Magic Eyes a lot, but I’m failing on this. (However, I found the difference in the coffee beans picture reasonably fast without the eye-crossing trick, and before reading what the difference is.)

I challenge you to use this refocusing ability to pass the Stroop Test: https://faculty.washington.edu/chudler/words.html

You are given a list of color names, written in font colors that are incongruous with the written word. E.g. "Red" will be written in a blue font, and "Green" will be written in a yellow font.

You have to say the font color and not the written word.

It's challenging, but it's yet another application where going cross-eyed confers an advantage.