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Recent discussions of the Schaie-Baltes controversy regarding the adequacy of various developmental designs are misleading because they fail to distinguish between description and explanation of developmental change. This distinction is reflected in the use of the General Developmental Model for the formulation of descriptive data collection strategies a la Baltes (cross-sectional versus longitudinal sequences) versus the formulation of explanatory data interpretation models a la Schaie (time-sequential, cohort-sequential, cross-sequential) which are aimed at identifying developmental origins for observed change patterns. When the objective is one of descriptive identification of individual-developmental change (but not necessarily of socio-cultural change), the age-cohort model is preferred with age-time and time-cohort models being approximations. A complete combination of cross-sectional and longitudinal sequences a la Baltes provides all data points needed both for descriptive and explanatory analyses. The distinction between descriptive and explanatory functions of Schaie’s model, prior to a given research project, helps to sharpen the issues, resolve the Schaie-Baltes controversy, and provides guidelines for applicative decisions.
Schaie et al. (2009) studied this question.