Kim Plunkett

Connectionism is a way of modelling how the brain uses streams of sensory inputs to understand the world and produce behaviour, based on cognitive processes which actually occur. This book describes the principles, and their application to explaining how the brain produces speech, forms memories and recognises faces, how intellect develops, and how it deteriorates after brain damage. Part I explores the basic concepts, the architecture and properties of the most common connectionist models, and how connectionist learning rules work. Part II describes and evaluates connectionist models of a variety of cognitive processes, including the learning and production of speech, the formation of episodic memories and visual representations, the development of cognitive processes in infancy, and their breakdown in brain-damaged patients. The models range from some well-known classics to others at the frontiers of current research. Each chapter ends with a list of recommended further reading. Also included is a disk with the software for running tlearn, a user-friendly simulator for connectionist modelling of cognitive processes, which will run on either PCs or Macs. The software includes exercises to introduce the simulator, and working copies to explore some of the models described in the text. A reference handbook for tlearn is included to enable readers to build their own models. The authors, as well as being leading researchers in their field, have extensive experience of teaching connectionism to undergraduates. They have written the first comprehensive, up-to-date textbook on connectionist modelling, designed specifically for advanced undergraduates, and accessible to those with only limited knowledge of mathematics. This will be an essential introductory text for all students in psychology or cognitive science taking a course on connectionism.

The majority of the world’s children grow up learning two or more languages. The study of early bilingualism is central to current psycholinguistics, offering insights into issues such as transfer and interference in development. From an applied perspective, it poses a universal challenge to language assessment practices throughout childhood, as typically developing bilingual children usually underperform relative to monolingual norms when assessed in one language only. We measured vocabulary with Communicative Development Inventories for 372 24-month-old toddlers learning British English and one Additional Language out of a diverse set of 13 (Bengali, Cantonese, Dutch, French, German, Greek, Hindi-Urdu, Italian, Mandarin, Polish, Portuguese, Spanish and Welsh). We furthered theoretical understanding of bilingual development by showing, for the first time, that linguistic distance between the child’s two languages predicts vocabulary outcome, with phonological overlap related to expressive vocabulary, and word order typology and morphological complexity related to receptive vocabulary, in the Additional Language. Our study also has crucial clinical implications: we have developed the first bilingual norms for expressive and receptive vocabulary for 24-month-olds learning British English and an Additional Language. These norms were derived from factors identified as uniquely predicting CDI vocabulary measures: the relative amount of English versus the Additional Language in child-directed input and parental overheard speech, and infant gender. The resulting UKBTAT tool was able to accurately predict the English vocabulary of an additional group of 58 bilinguals learning an Additional Language outside our target range. This offers a pragmatic method for the assessment of children in the majority language when no tool exists in the Additional Language. Our findings also suggest that the effect of linguistic distance might extend beyond bilinguals’ acquisition of early vocabulary to encompass broader cognitive processes, and could constitute a key factor in the study of the debated bilingual advantage.

This book is the companion volume to Rethinking Innateness: A Connectionist Perspective on Development (The MIT Press, 1996), which proposed a new theoretical framework to answer the question "What does it mean to say that a behavior is innate?" The new work provides concrete illustrations-in the form of computer simulations-of properties of connectionist models that are particularly relevant to cognitive development. This enables the reader to pursue in depth some of the practical and empirical issues raised in the first book. The authors' larger goal is to demonstrate the usefulness of neural network modeling as a research methodology. The book comes with a complete software package, including demonstration projects, for running neural network simulations on both Macintosh and Windows 95. It also contains a series of exercises in the use of the neural network simulator provided with the book. The software is also available to run on a variety of UNIX platforms.

Preliminary Approaches to Language Development