On the complexity of quantifying construct validity

To validate a measure of a construct is to validate a theory: The process includes theory specification, theory elaboration, choice of methods, choice of research design, reliance on necessary auxiliary theories, and empirical observation. Evaluating the success of the process is likely to be enhanced through quantification. To date, scientists have quantified the final step of empirical observation, but earlier steps in the validation process appear more difficult to measure. In this issue, D. Westen and R. Rosenthal (2005) emphasize that threats to validity are often methodological ones that precede empirical observation. Yet, their earlier attempt to quantify construct validity focused only on the final, empirical observation step of the process. For that reason, it can produce positive results despite real theoretical and methodological threats to validity. Nonetheless, the laudable attempt by these distinguished authors to quantify construct validity reminds us of the complexity of the construct validation process.