This course will provide an evolutionary theory of language as a complex adaptive system that exists as a cultural artifact without any requirement for innate abstract grammatical representations. Instead, language acquisition will be seen as an emotionally driven process relying upon an innately specified "interactional instinct." This genetically based tendency provides neural structures that entrain children acquiring their native language to the faces, voices, and body movements of conspecific caregivers. It is essentially an innate attentional and motivational system that drives children to pay attention to the language interaction in their environment and to acquire that language by general learning mechanisms that subserve declarative and procedural knowledge. This mechanism guarantees the ubiquity of language acquisition for all biologically normal children. Second language acquisition by older adolescents and adults no longer has recourse to this mechanism, and therefore, success in second language learning is extremely variable. Occasionally, however, affiliative bonds between second-language learners and target language speakers can be efficiently strong to recapitulate the attentional and motivational power of first language acquisition.