that portion of the image removes one of the strongest competitors for attention. The remaining forest can then be examined without the animal constantly pulling the gaze back toward the center of interest. This technique does not guarantee that the hidden face will appear, but it changes the visual competition within the picture.
Light and shadow deserve particularly careful attention. Hidden-image designs often depend on boundaries between brighter and darker areas because those boundaries can imitate the edges normally used to recognize objects. Snow naturally provides broad areas of brightness,
