Brian MacWhinney is Professor of Psychology, Computational Linguistics, and Modern Languages at Carnegie Mellon University. He has developed the Competition Model of first- and second-language acquisition, which shows how learning and processing emerge from competing patterns across divergent language levels and timeframes. He is the author of The CHILDES project: Tools for Analyzing Talk, 3rd Edition (2000) and editor of Mechanisms of Language Acquisition (1987) and The Emergence of Language (1999). He is also the creator of the TalkBank system for spoken language data-sharing.

William O'Grady is Professor of Linguistics at the University of Hawaii at Manoa. He has undertaken extensive research in syntax and language acquisition, focusing on the idea that linguistic phenomena are best understood in terms of the interaction of more basic factors and forces, especially processing cost. He is the author of numerous articles and books, including Syntactic Carpentry (2005), in which he first set out his ideas on the centrality of the processor to the study of syntax and language acquisition.