A visual test for negative afterimages uses an illustration of a specific flag. This flag has a green field and a yellow cross, which is bordered by black lines. The intersection of the cross is located slightly to the left of the flag's center, and a small white dot is placed at this intersection to serve as a focal point. This arrangement is designed to demonstrate the opponent-process theory; after staring at the dot for a period and then looking at a neutral surface, a person will typically see a negative afterimage with the opponent colors (a red flag with a blue cross).