Reported are implications of the genesis and development of joint action between Spanish adults and their infants for early first language acquisition. Focusing on the naturally occurring context of the "give and take" game format, this investigation discloses the role of the interaction pattern in the language acquisition process, including the beginning and development of query techniques, the linguistic and conceptual elaboration of terms associated with first actions, and the use of the first deictic terms. Observations support the view that very early in life infants find themselves involved in highly ranked joint action routines, the progressive mastery of which represents true "pragmatic learning." The practice of activities such as the "give and take game" allows the infant to dominate the course of action, thereby regulating its activity with an adult through the use of a vast set of communicative procedures. Over time, these procedures are generalized across similar situations, becoming "regulatory categories." In joint action the child elaborates notions, such as agent, action, receiver, place, possession, etc., and establishes many distinctions about its physical environment. Such distinctions are usually linguistically marked in the adult's language and provide easy access to grammatical specifications marking semantic relations. Once fundamental rules are mastered, specific joint action formats are expanded across a vast number of situations, thereby allowing greater linguistic complexity. (RH)