Now You See it, Now You Don’t: Interacting with Invisible Objects

There are some people who cannot see even with their eyes open. Although these people are blind, there is nothing wrong with the eyes themselves. Instead, there has been an injury to the part of the brain that helps them see: the visual cortex (this and all other words printed in bold font are explained in the Section “Glossary” at the end of this text). What is fascinating is that even though they cannot see, some of these people can reach out and grasp for an object correctly more often than if they were just guessing where the object was. Even more fascinating is an experiment showing that a person with this type of blindness can find his way down a long corridor and correctly avoid the obstacles placed along the path without using any help like a cane [1]. It seems as if these people are able to sense the objects that are invisible to them. Medically, this phenomenon is called “blindsight” [2]. What do you do when you are playing in the park on a hot day and your parents offer you an ice cream? Most probably, you go running to them, keep your eyes on the delicious ice cream cone, and reach out to take it from them. Although this feels like the most natural thing to do, it requires the fine coordination of your different sense organs and movements. You need your eyes (sense of vision) to look at the ice cream, your arms to reach out (motor system), and your hands (sense of touch) to hold it firmly. It seems obvious that in order to be able to reach out and grasp something, we need to first be able to see it and know where it is. Surprisingly, this is not always true.