Cognitive Development

Vygotsky believed the influence of the environment was crucial for development, whereas Piaget believed that the child's ability to independently explore her world was important. Although neither researcher emphasized the role of physiological changes in the brain and their contribution to a child's increasing ability to process information, neither would deny the significance of those changes for development. Information-processing theories attempt to account for changes in a child's cognitive ability via interactions between the developing brain and the child's increasing knowledge of the world. For example, researchers interested in these interactions may examine changes in working memory and how a child's world knowledge affects it.

Working memory (sometimes called short-term memory) is the memory that allows a person to remember a phone number that he has just looked up in the phone book. It involves mental rehearsal processes that maintain the information in memory. The capacity of young children's working memory is under debate. Early on, researchers measured the number of digits children could remember. Results FIGURE 2 Study in which infants were tested for object permanence using the habituation-dishabituation response. (a). First, infants were habituated to two events: a short carrot and a tall carrot moving behind a yellow screen, on alternate trials. Then two test events were presented, in which the color of the screen was changed to blue to help the infant notice that now it had a window. (b). In the possible event, the short carrot (which was shorter than the window's lower edge) moved behind the blue screen and reappeared on the other side. (c). In the impossible event, the tall carrot (which was taller than the window's lower edge) moved behind the screen, did not appear in the window, but then miraculously emerged intact on the other side. Infants as young as three-and-one-half months dishabituated to the impossible event. This suggests that young babies must have some notion of object permanence—that an object continues to exist where it is hidden from view. (Adapted from R. Baillargeon and J. DeVos, 1991, "Object Permanence in Young Infants: Further Evidence." Child Development, 62, p. 1230. ©The Society for Research in Child Development. Reprinted by permission.) from this work suggested that children had a smaller working memory capacity compared to adults. For example, participants were asked to listen to a list of single digits and repeat them back in the order they had heard them. Researchers found that adults could typically remember between five and nine digits and children typically remembered about three or four.

Despite this clear result, other researchers, such as Robbie Case, argue that the overall capacity of working memory does not change over the course of development. What changes is the child's ability to efficiently process information. For example, in order to perform well on a digit span task one has to represent the numbers in some way. Adults and older children can quickly repeat the numbers aloud or in their mind. Case, D. Midian Kurland, and Jill Goldberg found that young children take longer to repeat a number. Therefore more of the young child's resources are taken up with saying the numbers than with efficiently remembering them.