Improving construct validity: Cronbach, Meehl, and Neurath's ship.

Smith's article "On Construct Validity: Issues of Method and Measurement" is a fine tribute to L. J. Cronbach and P. E. Meehl (1955) that clarifies the current state and future directions in the understanding of construct validity. Construct validity is a dynamic process, and fit indices need to be used at the service of understanding, not in place of it. The failure of a study or set of studies to support a construct, a measure, or the theory underlying it admits of many explanations, and the ways scientists interpret such failures are prone to cognitive biases and motivated reasoning. This suggests why metrics designed to index the extent to which observations match expectations can be useful prostheses to scientific judgments. As P. E. Meehl (1954) showed decades ago, quantitative, statistical formulas and indices tend to outperform informal, qualitative judgments, and this applies as much to the way researchers evaluate constructs and measures as to judgments in the consulting room.