This amazed me. I could not see it until I squinted, and then it was obvious, and it was still obvious when I opened my eyes. For a second, and then it disappeared again. Weird.
Several other people on Facebook have reported back. Some were able to read it at first glance, others had a hard time. Jody wrote about her experience:
Yes, squinted the first time. Later the light changed, I walked into the room, squinted from afar and saw it at once. But today it had disappeared again for awhile. Then I moved back (more afar from the screen again) and the black text emerged. However, just this moment I looked again and only could see the white part. That's what it's about, seeing the white or the black. How this has to do with the brain, I can't imagine. Just now, I tried to focus on the black and couldn't get it again! Have I gone mad? (There's something eerily 3-D about it too. Recently I came across an Indian yantra that, when stared at, is said to balance the right and left hemispheres of the brain. Maybe this exercise is jumbling my brain halves aound.)