Adult reformulations of child errors as negative evidence This research was supported in part by grants from the National Science Foundation (SBR97-31781), the Spencer Foundation (199900133), and the Center for the Study of Language and Information, Stanford University, to the second author. We thank Jeanene Harlick, Meleah Hill, and Sayra Khandekar for help in coding data; Ewart A. Thomas for invaluable statistical advice; William Croft, Zenzi Griffin, and Ellen M. Markman for comments on earlier versions, and Herbert H. Clark for insightful suggestions. We would also like to thank two anonymous reviewers whose comments helped us clarify our arguments.