appropriate, practical, cost-effective, and, above all, compatible with colony management and the conduct of research. Although professional judgment and lay judgment will continue to have their roles in programs to monitor and enhance the well-being of laboratory primates, intuition and personal judgment should be viewed as adjuncts or as the first step of hypothesis formation, not as a substitute for scientific investigation. Enrichment methods that have not been subjected to empirical testing should be viewed simply as invalidated ideas, regardless of how well intended they might be. Without appropriate measurement and verification, we might do more harm than good in our efforts to improve animal conditions.
With an eye to achieving a better and, insofar as possible, a scientific perspective of psychological well-being, we propose the following topics for research. We recognize that the list is not all-inclusive.
The phrase psychological well-being arose in a regulatory, rather than scientific, context. Psychological well-being is a hypothetical construct, and the validity of a hypothetical construct can be determined only in relation to a theory that defines its properties and in relation to empirical data that address the fit between predicted and observed phenomena. We do not have a theory to guide thinking and research on well-being; the development of a coherent theory of psychological well-being is an obvious research need. Such a theory ought to incorporate cognitive, behavioral, and physiological characteristics of the organism in an integrated view of well-being. It also ought to encompass the possibility of species, age, sex, and individual differences in responsiveness to the same immediate environmental situation. Some of the work that has been done so far in this domain is based on notions of how humans behave and how they react to environmental situations. That might be a suitable place to begin the development of hypotheses, but it clearly is not sufficient. We must develop a theory so that we can agree on empirical measures of well-being, rather than relying on conflicting subjective judgments about internal states in other species.
The acceptance of particular behavioral or physiological measures as operational indexes or correlates of psychological well-being can follow only from a theory that defines well-being in compatible terms. The use of multiple measures of psychological well-being until such a theory has been developed has been advocated. However, the relationships among several commonly used measures are not well understood. For example, chronic stress has both behavioral and physiological components, but their interrelationships have not been characterized fully. Furthermore, if stress is considered a manifestation of ill-being under