The stream of our consciousness contains an almost unceasing parade of sensation-like experiences, even in the absence of any external stimulation to produce them. We experience picture-like things, sound-like things, and more; our experiences can resemble any of our sense modalities. These experiences are what we refer to by the phrase "mental imagery." The images need not be vivid. People who doubt that they experience visual imagery are often persuaded by a simple exercise: count the windows of the house in which you live. Nearly everyone performs this task by walking around the house in imagination while counting windows, or by walking through the house counting them from the inside. The imaginary windows seem to be set in visual space. There is a temptation to point at them with an index finger while one counts, even though the images may never become vivid enough to seem like an actual visual experience. But if they seem set in visual space, if they can be pointed at, they clearly constitute a sensory-like experience in some meaningful way.