Luminous stains stuck to the window

The New Yorker:

Kosslyn believes that any improvements in mental imagery will require a “catalogue of visual memories” that can then be used to build expectations about the visual world. “When you develop expectations, you can use the fruits of previous experience to help you process what’s coming in now,” Kosslyn said. “But you need to have had that experience.” An example is depth perception: to the sighted, with a lifetime of practice, rules about occlusion (if A occludes B, object A is closer) and foreshortening (objects farther away appear smaller) are continually used to combine incoming light into a rich, three-dimensional world. The absence of these rules can frustrate the newly sighted, whose visual world can be both blurry and two-dimensional—paintings and people are often described as “flat, with dark patches”; a far-away house is “nearby, but requiring the taking of a lot of steps”; streetlights seen through glass are “luminous stains stuck to the window”; sunbeams through tree branches collapse into a single “tree with all the lights in it.” (The writer Jorge Luis Borges, who went blind at age fifty-five, described going blind as a process by which “everything near becomes distant.” In the newly sighted, without depth perception, the opposite seems true: the distant—tiny houses on the horizon, clouds in the impossibly high sky—suddenly looks nearby.)