This book has two aims: to set forth a description of changes in logical operations between childhood and adolescence and to describe the formal structures that mark the completion of the operational development of intelligence. To tie these together the authors have tried to present the material in a way that would stress the close relationship between the two. Each of the first fifteen chapters (Parts I and II) includes an experimental part by the first author and a brief final analysis by the second author. This analysis aims to isolate the formal or propositional structures found in each case. Chapters 16 and 17 (beginning of Part III) are the work of the second author, whereas Chapter 18 is a joint production. In addition, the specific problems of experimental induction analyzed from a functional standpoint (as distinguished from the present structural analysis) will be the subject of a special work by the first author. (PsycINFO Database Record (c) 2004 APA, all rights reserved).