electrical activity during thinking, both with and without verbalization and the use of language. Although seemingly simple, these experiments tackle a very complex subject with which psychologists, linguists, and others are only beginning to come to grips. Sokolov and his group have succeeded admirably in splitting the subject apart by driving in the wedges of objective measurement and unique experimental formulations. Chapter IX dips into the neurology and neurophysiology of motor speech and its feedback mechanisms and the dynamic localization and organization of the cerebral mechanisms responsible for symbolic formulation of speech and thought. The bibliography brings together a considerable number of Russian publications on this subject, as well as some of the pertinent American and European literature. This book is a welcome addition to an important field. Donald B. Lindsley Professor, Departments of Psychology, Physiology, and Psychiatry, and Member of the Brain Research Institute, University of California, Los Angeles Contents Introduction .......................................... . Part One GENERAL PROBLEMS OF STUDY Chapter I Theories of the Interrelation of Speech and Thought ............... 11 Chapter II The Problem of Inner Speech in Psychology ..................... 34 l. Early Investigations of Inner Speech ..................... 34 2. Discussion of Inner-Speech in Soviet Psychology ............ 46 3. Verbal Interference Methods in the Study of Inner Speech ..... 52 4. Detecting Concealed Speech Reactions by Conditioned-Reflex Methods ........................................ 58 5. Conditioned Reflexes to Numbers ...................... 61 6. Clinical Observations . . . . . . . . . . . . . . . . . . . . . . . 61 . . . . . . . .