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In Defense of Qualitative Changes in Development


  • I thank Richard Aslin, Susan Carey, Leslie Cohen, Marshall Haith, David Moore, Charles A. Nelson, Nora Newcombe, J. Steven Reznick, and Jay Schulkin for comments on an early draft. The incentive for this article was a dinner conversation with Michael Lewis at the 2007 meeting of Society for Research in Child Development in Boston.

concerning this article should be addressed to Jerome Kagan, Department of Psychology, Harvard University, Cambridge, MA 02138. Electronic mail may be sent to


The balance between the preservation of early cognitive functions and serious transformations on these functions shifts across time. Piaget’s writings, which favored transformations, are being replaced by writings that emphasize continuities between select cognitive functions of infants and older children. The claim that young infants possess elements present in the older child’s concepts of number, physical impossibility, and object permanence is vulnerable to criticism because the inferences are based primarily on the single measure of change in looking time. It is suggested that investigators use unique constructs to describe phenomena observed in young infants that appear, on the surface, to resemble the psychological competences observed during later developmental stages.