We look for differences in texture, color, and light when we try to pick objects out of a background jumble. When there are little or no visual differences between the object we seek and the background colors and textures we are apt to have trouble seeing the object.
The image on the left is an extreme example. All color clues have been removed and a lot of the familiar detail is missing as well. Whatever the object is—it is well camouflaged. Can you tell what it is?