“The mirror test . . . is a behavioral technique developed in 1970 by American psychologist Gordon Gallup Jr. . . . In the classic test, an animal is anaesthetised and then marked (e.g., painted or a sticker attached) on an area of the body the animal cannot normally see. When the animal recovers from the anaesthetic, it is given access to a mirror. If the animal then touches or investigates the mark, it is taken as an indication that the animal perceives the reflected image as itself, rather than of another animal . . . Very few species have passed the test.” - Wikipedia