In celebration of Language Learning's 60th anniversary in 2008, the journal hosted a conference at the University of Michigan on the theme of "Language as a Complex Adaptive System." Leading researchers in linguistics, psychology, and complex systems discussed the path-breaking significance of this perspective for their work, demonstrating that an understanding of language learning can only come about from such interdisciplinary, integrated inquiry. The papers in this volume summarize this new approach and illustrate it as it applies to language usage, structure, and change, sociolinguistics, cognitive linguistics, anthropology, language evolution, first language acquisition, second language acquisition, psycholinguistics and language processing, language education, individual differences, and language testing.