When Bill looks at his lamp alternately with his left eye and right eye, the image seems to jump from one position to another. This phenomenon illustrates ______________

A) retinal disparity
B) convergence
C) divergence
D) interposition

Answer: A
Rationale: Retinal disparity (or binocular disparity) is the difference in relative position of an object as seen by both eyes, which provides information to the brain about depth. In this example, closing one eye and then the other allows bill to notice the slight difference (disparity) in how each eye views the lamp.