Some say that the theory of special abilities died a hundred years ago; others that it is the only sound approach to a better understanding of the human mind. This book describes experiments which have led to the discovery of seven elements of the mind and to the partial isolation of two others. It is written primarily for the scientist who is interested in an approach to psychology which may do for that subject what the discovery of the elements did for chemistry. In addition, it is of interest to the general reader as the first groping steps in a new science and as a description of the experiments on which is based the work of the Human Engineering Laboratories. It should be read by everyone who is interpreting psychological results in schools or industry.