The University of Manitoba Symposium on Pupillometry was held in Winnipeg, Manitoba, October 17-19, 1973. The seed of the idea was planted in 1967 when Raymond Daly of the University of Windsor first interested me in the utility of the pupil as a dependent measure in psychology. From that time on I have read as much as possible about the pupil and in late 1971 it occurred to me that it might be a good idea to bring together those pupil lary investigators whose research had the greatest impression upon me. This book is one of happier consequences of the Symposium. The guiding principle behind the selection of participants was a blend of three considerations: (1) long standing research or scholarly interest in problems associated with the eye and the pupil; (2) outstanding respect of the participant by his colleagues involved in pupillometric research; and (3) significant contributions to the learned literature.