"This book is the first detailed description of a particular theoretical framework for studying language development and language performance. The framework is called MOGUL (Modular On-line Growth and Use of Language). It has been the topic of numerous publications and presentations since the appearance of our 2004 keynote article in Bilingualism: Language & Cognition. MOGUL is not just about how a language grows in the individual child: it is about how the mind expands to accommodate more than one language both in childhood and later in life and how these various linguistic systems share space and interact"--