For many animals including humans, the ability to identify different individuals among their own kind is an essential ability for everyday living. Faces are the most important body part for individual recognition in many animals, and faces are special in many ways. For example, humans and some other mammals not only look at the parts of a face (such as eyes and nose), but read the face as a whole. When we see an upside-down face, it is more difficult to recognize it because our ability to read the face as a whole is interrupted (Face inversion effect). This special ability only occurs in faces and not in other objects.