When you throw a ball at a target, many different parts of your brain are working together. Your eyes and visual systems give your brain information about where things are, while your proprioceptive systems give your brain information about where your body is in space. Your motor systems use all this information to produce movement, so you can throw the ball in the right direction.
When you first put on the goggles, the ball doesn’t go where your eye says it should. Because of the way it refracts, or bends, light, the prism makes objects in front of you appear to be to one side. Light travels from the target to your eye along the path shown by the arrows in the diagram below (click to enlarge).
As light passes through the prism, it is bent twice—once when it enters the prism and again when it leaves. Your eye-brain system tries to follow this light back to its origin in order to locate the target, but it doesn’t have the ability to recognize that the light was bent. It follows the light back along a straight line defined by the ray of light that enters your eye, and so the target appears to be somewhere on this line.
At first, your throws probably miss the target by a lot. Your brain, however, soon adapts to the distortion produced by the goggles, and your visual and motor systems make adjustments. You begin to aim farther to the side and get closer to hitting the target.
When you remove the goggles, your brain remembers the prism distortion, and it functions as if the goggles were still in place. It may take a few trials for your brain to “unlearn” the adjustments it made and return to normal. Your experience with the goggles shows that your brain and and its different systems are dynamic: They continually respond and adapt to your experiences, whether or not you’re thinking about them.
You forced your eyes and brain to adapt when you put on the goggles. But your brain is challenged on a daily basis to relearn skills and change the way it processes information—all it takes is driving someone else’s car, taking a new route to the grocery store, or putting your toothbrush in a new location. If we did not have the ability to adapt to changes in the world (or to changes in our perception of the world), life would be much harder.