The spontaneous speech of three Mexican American children (one boy and two girls) and their mothers, siblings, relatives, and neighbors was recorded to investigate the relationships between language and cultural values and beliefs, and between language, input, and cognition and the acquisition of linguistic forms. The children were first-born, 20, 24, and 26 months old at the start of the study, and just beginning to produce two-word utterances. They had a younger sibling born when they were 23 to 32 months old; their mothers were the primary caregivers. Two recordings, 1-5 days apart, were made every three weeks, each for two hours, totaling 134 hours. The boy was taped for 9 months and the girls for 12 months during meal and bath times, play with peers and parents, visits with friends and relatives, outings to the park or store, and television-watching. Findings indicated that input language was a powerful socializing force through which adults directed the children's behavior and taught them what was important to know, do, talk about, and feel; and that there was a clear relationship between the contexts in which children were directed to speak, beliefs about appropriate behaviors for children, and other behaviors of the adults in interacting with the children. (NQA)