Well known for their work in first language (L1) acquisition, Crain and Thornton (henceforthC&T) have produced with their Investigations in Universal Grammar a thoroughreview of the innovative experimental techniques they developed to investigate the acquisition ofsyntax. In this sense, the volume would appear to be a kind of research-methods book. Thevolume is a great deal more, however. Indeed, in the volume's three main sections (16, 8,and 16 chapters, respectively), C&T present examinations not only of the nature ofhuman-language grammars but also of the factors that conspire to result in linguisticperformance. What makes the C&T volume superior is that they integrate theoreticalframework with methodological practice so seamlessly.