Blake Ross and I have something in common. We've both learned a fact that blew our minds. The thing is, it blew our respective minds for opposite reasons. Ross suffers from a condition called aphantasia: the inability to form mental images. He describes it as being blind in your mind.
The startling revelation is that Ross is 30 years old and has just learned that not everyone is like him. Likewise, I was shocked to discover that this condition, far from being the rare result of a physical trauma, is perhaps not common but far from uncommon. Studies show that perhaps 2% of the population suffer from aphantasia.
Ross's post is a long description of what it's like to be unable to visualize things in your mind. It's more than being unable to imagine a beach scene. Ross can't recall his father's image or even “see” a triangle in his mind. Those of us who don't suffer from aphantasia find it difficult to imagine what it's like but Ross does a good job of describing it. To me, the astounding thing is that he was 30 before he discovered that most people are constantly forming mental images.
Read his post; you'll find it fascinating. I especially enjoyed the reactions of his friends when he started asking them about it.