Interesting fact:

Remarkable, no? This is a visual trick known as a ‘Troxler Effect’, because, as you’d imagine, it was invented by a dude named Troxler. It demonstrates how our brains cope with the thousands of sensations they are regularly exposed to. By focusing on what is seen as the more important information – in this case, the more vibrant dot in the center – our brain filters out the “unnecessary” information, thus making it seem as if the blue line is vanishing. Our brain does this all the time. Weird when it’s called into focus, isn’t it?