LOOK AGAIN
Illusions Test Visual Perceptions.
The brain’s role in constructing meaning out of what you see is easily demonstrated by optical illusions.
Illusions can emerge from retinal processing of the visual primary colors of red, green, and blue in the eye’s cone cells, or deeper in the brain’s neural networks.
Two good examples of illusions resulting from neural processing are the Necker cube and Ames room. The former takes its name from the Swiss crystallographer Louis Albert
Necker, who was looking at a cubic crystal through a microscope in 1832, when the back and front sides of the cube seemed to spontaneously flip.
Necker repeated the illusion by devising a simple drawing of a transparent wire-frame cube whose perspective shifted as he gazed upon it.
The viewer’s brain imposes order on the cube by selecting one face to be the one closest to the eyes. However, in short order, the brain switches orientation, sending the previously fore- most square face to the back side.
The brain chooses one perspective or the other, and cannot hold both images in mind at the same time.
The Ames room, named for inventor Adelbert Ames,Jr., is a grossly distorted room of trapezoidal shape that, when viewed from one point directly front and center, appears to have normal right-angled walls, floor, and ceiling.
One corner opposite the viewer is much farther away than the other, but clever manipulation of perspective makes the room seem rectangular with the far wall parallel to the room’s front.
A person in the far corner seems tiny while another person in the near corner appears gigantic; walking from one corner to the other makes a person appear to grow or shrink.
The illusion works because the brain insists that the room must be a three-dimensional rectangular shape, which it has been conditioned to expect.