Piaget's famous 3 mountains task apparently showed that children under the age of 8 are egocentric, that is they do not realise that other people see things differently to themselves. In the three mountains task a child is seated in front of a papier mache model of 3 mountains and a doll is seated on one of the other 3 sides of the model. The child then has to choose from a series of photographs, the one that shows the dolls view - children under 8 usually choose the photograph that shows their own perspective. Other examples of egocentrism include children hiding by burying their heads in the sofa - if they can't see you then you can't see them. However, new research by psychologists at the University of Washington's Institute for Learning and Brain Sciences indicates that even 12- and 18-month-old babies not only are observing what is going on around them but also are using their own visual self-experience to judge what other people can and cannot see.