In neurotypical infants, genetically-specified attachment/attention mechanisms underpin the motivation to interact, which enables the acquisition of socio-cultural norms for language and accounts for the efficacy of socialization processes (Lee et al., 2009; Schumann, 2013). In children with autism, as in second language acquisition, neurodevelopmental differences in attachment/attention mechanisms may result in a diminished drive to interact, thus hindering the acquisition of socio-cultural norms for language and limiting the efficacy of language socialization (Lee et al., 2009; Schumann, 2013). This dissertation applies this theory of an "interactional instinct" (Lee et al., 2009), beginning with a review of its relevance in societies that predominately practice polyadic and often subdued infant-caregiver interactions when compared to dyadic, face-to-face interactions that are typical in Western societies. It offers evidence that the uniformity of primary language acquisition can be explained because the language socialization that infants experience is commensurate with what they need in order to become competent language users in their communities. Three qualitative studies then follow. In the first study, infant language acquisition is analyzed in terms of a clean-up routine at a daycare. A close examination of non-vocal and vocal exchanges between a teacher and a neurotypical 14 month old demonstrates how affiliative cues may help to sustain the infant's on-going opportunities for language learning. In the second study, the efficacy of a language intervention for minimally-verbal older children with autism is presented. How conversational and discursive structures relate to desired therapeutic outcomes are described, especially in terms of eliciting and increasing boys' participation in play routines with therapists. In the third study, the experiences of parents and their children with autism who attend a basic-skills training program in India are examined. The core components of the training link to neurobiological accounts of language acquisition, and participants' experiences in these areas suggest instructional strategies for those providing support to individuals with autism, even in under-resourced areas, as well as second language teachers for older individuals. The review and the three studies address the topic of language access, or opportunities to participate in community activities, that language learning requires. In particular, they describe how affiliation in everyday interactions between teachers/therapists and learners promotes language access, regardless of age or ability. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]