 When looking at a single object, some points on the object stimulate both eyes, but some points stimulate only the right or the left eye. The brain resolves these common and distinct stimuli into a single image (Hershenson 1999, 29–30). The fact that the brain must resolve two distinct images into one accounts for the horopter effect. When the eyes are focusing on a single point, the left and the right eyes give different inputs to the brain about objects to the left or right of the point of focus. The brain corrects for the different inputs coming from the left and the right eyes by representing them as equally distant from the eyes as the object of focus.