This volume was designed to focus on the problems of perception and originally was to have been solely edited by Professor Hans-Lukas Teuber who was a member of the editorial board which initiated production of the Handbook. Accordingly, he issued invitations to a number of researchers III perception asking them to contribute chapters written in a style described III his words: " . . . Ire hope that no author lI'ill feel COl/strained to undertake a major search of the literature: he could In'ite, instead. on an area in which he has been quite actire himse?t~ and II'here most of the issues are immediately obt"ious to him. In this Iray, the IITiting of the chapter should be cnjoyable rather than a chore . . it should result in a personal account of the state of a given area rather than in an encyclopedic treatise . . . the field deserves this sort of summary ret'iell", particularly (f it is pointed toward the future and speeds the convergence of det'elopments in sensory physiology and psychological studies of perception, " With the growing burden of national and international commitments includ­ ing departmental headship, Professor Teuber felt that it would be wise to share the editorial responsibilities for this volume and accordingly, asked Professors Richard Held and Herschel Leibowitz to co-edit the volume with him in the same spirit as outlined in his invitation to authors. They agreed to help in this task.