In Chapters 11 and 12 we considered how animals and people use vision to control their actions in the physical world of surrounding surfaces and objects. For people and for many animals, vision is also important in moving through the animate world of other creatures with which they must interact in some way. For animals, these can include prey or predators, and members of their own species with which they mate, fight, or cooperate. For people, the social world is more complex still. Our interactions with other people are guided by shared knowledge and understanding, and mediated largely through language. Even so, they do rely on the same basic abilities that some animals possess; to recognise the identities, actions, and intentions of others and to respond appropriately. Although we obtain much of this information from what other people say to us, visual perception of their actions is also important, especially in situations where we adjust our own behaviour rapidly in response. Imagine for example a football (soccer) player watching the glances and changes in posture and running direction of other players, and using this information to make rapid decisions about where to run, how to kick the ball, and so on.