NGeo Video: Self-Recognition in Apes
You may have read about the "mark test" or "mirror test." It's a way scientists study self-awareness or self-recognition. They surreptitiously put a colored dot or other mark on a subject -- often somewhere on the face. If, while looking in a mirror, subjects touch their marks or adjust their position to see them better, it's clear they understand they're looking at an image of themselves, rather than at other beings. Species that have passed the mark test include all great apes, bottlenose dolphins and magpies.
If you're curious to see the test in action, below is a video from National Geographic that features an orangutan as test subject.