Another kind of evidence concerns adults learning to perceive differently using artificial devices. A number of experiments have explored perceptual learning by designing and using various kinds of goggles to alter the way in which things appear to those wearing them. Sometimes the goggles rotate the field of view so that, for instance, everything seems to be upside down or shifted to one side. A prism is often used. The goggles are sometimes worn for several weeks.
Wearers typically report that the world at first seems very unstable.
Some people can perform simple skills after only minutes of practice. After a few days it is often possible to do such things as riding a bicycle, and after a few weeks even skiing may be possible for those who could ski beforehand. After taking off such goggles, the world again seems to be unstable, though typically recovery occurs within an hour or so. You can simulate the early stages of using such spectacles by looking up at a hand-mirror slanted against your forehead and tryint to do such things as pouring water into a cup.