blindness/seeing
Blind children playing hide-and-seek. Found here. See also: Blind Children Studying the Hippopotamus, Blind Children Studying the Globe.
Annie Dillard in her essay "Seeing," reporting on Space and Sight, a case-study of the newly-sighted (by means of cataract-removal surgery), by Marius von Senden:
Many newly sighted people speak well of the world, and teach us how dull is our own vision. To one patient, a human hand, unrecognized, is "something bright and then holes." Shown a bunch of grapes, a boy calls out, "It is dark, blue and shiny....It isn't smooth, it has bumps and hollows." A little girl visits a garden. "She is greatly astonished, and can scarcely be persuaded to answer, stands speechless in front of the tree, which she only names on taking hold of it, and then as 'the tree with the lights in it.'" ... One girl was eager to tell her blind friend that "men do not really look like trees at all," and astounded to discover that her every visitor had an utterly different face. Finally, a twenty-two-old girl was dazzled by the world's brightness and kept her eyes shut for two weeks. When at the end of that time she opened her eyes again, she did not recognize any objects, but, "the more she now directed her gaze upon everything about her, the more it could be seen how an expression of gratification and astonishment overspread her features; she repeatedly exclaimed: 'Oh God! How beautiful!'"
Everyone who hasn't already should probably seek out and immediately read this essay. You will find it in Pilgrim at Tinker's Creek.