The art and science of visual illusions.

Mit Widmung des Autors f�r Walter Ehrenstein. - This book spans thegap between the artist'sand the scientist's approach to visual illusions. By adoptingthe visual'language'of the former and the vocabulary of the latter, complex and intriguing designs are described in terms of theconcepts of visual science. Hitherto, psychologists have tended to concentrate on relatively small spatial illusions, and tofavourtheir representation in such extreme simplicity that there has been little in them toexcite visual artists. Initially, the variety of visual effects manipulated in Op Art are described and profusely illustrated by the author's own designs. The spatial �llusionsfamiliar to psychologists are then depicted usinga novel technique of superimposing one design, printed on a transparent overlay, on top of another: the lines of the transparency may be distorted in size, shape or orientation. More complex illusionsthan have yet been employed in either context are presented in the final section. Theseare produced by combining, within the same illustrations, the spatial distortionsofthe psychologists with the op-tical illusionsof theartists. Both two-and three-dimensional illusionsare included, makingthe book so rich in visual puzzles that it will delight the layman as much as the psychologist or artist. All the phenomena demonstrated illuminatethe characteristics of human vision, and existing theories to explain them are described and assessed.