Quantitative Investigation of the Lawfulness of Simultaneous Brightness Contrast

Abstract

PREFACE Seventy-five years ago Carl Hess and Hugo Pretori published their classical experiment on simultaneous brightness con t ra s t .3 ince then there have been many experiments on the subject, but perhaps none has been as complete as theirs. Their experiments still shape some conceptualizations of simultaneous contrast and continue to be cited in the literature. In fact, over the past 15 yr. the citation of Hess and Pretori has nearly become a sine qmz non of the simultaneous contrast literature. In view of this it seemed that a rendering of Hess and Pretori into English was long overdue. Some psychologists tend to consign anything that is 75 yr. old to the domain of the historian. But Hess and Pretori's work differs little from today's investigations of simultaneous contrast. It is true that the modern investigator seems to prefer the dichoptic method of viewing, where the two fields are projected to non-corresponding retinal tissue in the contra-lateral eyes. This preference removes the possibility of intra-retinal interactions among the inputs. Nevertheless, given the width of the surround fields and the large separation that Hess and Pretori maintained between their two infields, it may be that they avoided significant intra-retinal interactions with their monocular method. Whether that is the case has yet to be established empirically. Hess and Pretori were continuously aware of numerous methodological and procedural difficulties in investigating simultaneous contrast effects. Their comments about the possibility of small extraneous bands between focal and sur-