  Wynn (1992) showed that young babies represent objects as not only persisting in time and space, but also as subject to addition and subtraction. In that study, babies were habituated to a display of a single object on a stage. Then a screen came up and hid the object completely. Now a hand was seen to bring in another (identical) object and move behind the screen, from which the hand then withdrew empty. The question was: do the babies now represent 2 objects behind the screen? Test displays consisted of 1 object, 2 objects, and 3 objects. Again, in line with Nativist claims, babies showed longer looking times to all displays except the 2-object display. In this respect, babies showed the same expectations that adults do. Further testing showed that babies are not only capable of ‘adding up’ the number of hidden objects (at least to 3), but are also capable of ‘subtraction’ of the same number of hidden objects as well. This finding has been replicated in 4- and 5-month-olds as well (Simon et al. 1995; Koechlin et al. 1998).