Is native speaker variation in understanding complex sentences due to individual differences in working memory capacity or in syntactic competence? The answer to this question has very important consequences both for theoretical linguistics and for educational practice. This book is distinctive in giving an historical and interdisciplinary perspective on the rule- based and experience-based debate. It is also highly unusual in supporting an account based on integrating explanations from both traditions. In the study reported here, variation in comprehension was found to be due to differences in syntactic competence and the author argues that sentence comprehension is a learned skill, displaying many of the general characteristics of cognitive skills His study also suggests that poor linguistic competence can be improved through appropriate teaching in school .The book will be stimulating reading for psycholinguists, theoretical linguists, applied linguists and educators.