The document summarizes the origins and development of research on interaction and second language learning. Early studies examined modifications in native speaker (NS) input to non-native speakers (NNS) and differences between baby talk and foreigner talk. Later research found NS modifications could negatively impact NNS participation and argued NNS-NNS interactions provide more opportunities for negotiation of meaning. Additional studies explored the importance of learner output in interaction and comprehensible output for second language acquisition.