Originally published in 1892, this groundbreaking work on perception and experimental psychology is a foundational text in the field. Fullerton and Cattell's research into the human senses and the perception of small differences set the stage for future discoveries in the field of psychology. This edition includes a new introduction by a leading cognitive scientist, making it an essential resource for anyone interested in the history of psychology. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.