This volume is the seventh in an ongoing series addressed to the in psychological assessment. The overall aim of the developing frontiers series is to bring critical examinations of recent advances in assessment to clinicians, researchers, university teachers, and graduate students, and thus to help them to keep abreast of an important and rapidly expanding field of psychology. This aim of course cannot be fulfilled in a single volume, but it can be met, at least to a large degree, in a continuing series. In this context we encourage those readers who are pleased with the offerings in this volume to consult appropriate chapters in earlier volumes of the series. The term psychological assessment, as used in this series, encom­ passes all of the various techniques - tests, rating scales, interview schedules, surveys, direct observational methods, and psychophysiol­ ogical procedures - that are employed in scientifically based practice and research to provide an improved understanding of individual persons, groups, or environmental settings. Thus, the whole field of assess­ ment is taken as the proper area of concern for the series. This includes both what are sometimes called traditional assessment and behavioral assessment, as well as approaches not typically classed in either of these categories.