An approach to the attribution of aging, period, and cohort effects

To extricate the inherently confounded factors of maturation, cultural change, and generational differences, life-span methodologists have proposed a variety of analytic designs and interpretative decision rules. Recent critiques have shown that the proposed rules are inadequate and that there are logical limits to any such set of rules. A number of alternatives have been offered, most of which require the investigator to have strong, theoretically guided hypotheses and presume that the data conform strictly to the demands of the design. This article addresses the common situation in which data analysis is exploratory rather than hypothesis testing and in which the model is applied to data that only loosely meet the requirements of the design. In this case, aging, period, or cohort effects can be inferred if the researcher is willing to make appropriate restrictive assumptions and use scientific judgment rather than fixed decision rules. The application of judgmental principles is illustrated on 2 longitudinal data sets, and it is argued that the analytic designs are useful if intelligently applied and interpreted. (32 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved).