A measure of mothers' encouragement of child-generated verbal responses was derived from videotapes of 66 mothers teaching a block-sorting task to their 4year-old children. The children were given a number of tests when they were 3 years 8 months, 4, 5, and 6 years old. Correlations and partial correlations of mothers' encouragement of verbalization with children's knowledge of letters and numbers were significantly stronger than those with Verbal and Performance IQ, which were nonsignificant. This pattern of correlations is consistent with a specific verbalization-helps-memory-of-content mechanism and inconsistent with a more global verbalization-generally-helps-thinking mechanism.Certain kinds of language experiences are widely believed to influence children's intelligence and school achievement. Because some aspects of language reflect socioeconomic differences among families, children's language experiences are regarded as partly determining social class differences This article is based on U.S. data from a cross-cultural study of cognitive socialization, which is a collaborative effort between U.S. researchers led by Robert D. Hess and Japanese researchers led by Hiroshi Azuma, a professor in the Faculty of Education at the University of Tokyo. Keiko Watanabe of the Japanese team collaborated in developing the coding framework for the mothers' verbal behavior. Other U.S. participants are