In this article, we explore theory-driven hypotheses linking ecological change with changing patterns of socialization. These studies are part of a larger project begun by Garcia in 2004; it aims to assess the effects of social change on Millard Madsen’s experimental findings concerning social behavior and socialization strategies in different regions of Mexico in the 1960s and 1970s. The present two studies apply Greenfield’s theory of social change and human development to maternal socialization in San Vicente, Baja California, Mexico. As San Vicente’s population, commercial activity, modern technology, and connections (through immigration and television) to the United States grew, maternal socialization shifted. Mothers’ behavior as their children played two beanbag games developed by Madsen and Kagan revealed that, over a 43-year period, San Vicente mothers became less giving while augmenting their use of achievement-promoting behavior in several ways: In Study 1, mothers in 1972 were more generous in giving their children rewards, compared with mothers in 2015; the 2015 mothers had also become more selective in preferentially rewarding children’s successes rather than failures. In Study 2, mothers in 2015 set higher goals for their children than did mothers 43 years earlier.