 If not all perceptual development is learned, while all perceptual learning is learned, then there is a distinction between perceptual development and perceptual learning. One way to draw the distinction more fully is the following. Perceptual development involves perceptual learning. However, it does not just involve perceptual learning. It also involves what is called maturation. For instance, the abilities that Kellman and Garrigan describe above (object perception, the perception of faces, the perception of three-dimensional space, etc.) fall under the category of maturation.