Reference. Schipolowski, S., Schroeders, U., & Wilhelm, O. (2014). Pitfalls and challenges in constructing short forms of cognitive ability measures. Journal of Individual Differences, 35, 190–200. doi:10.1027/1614-0001/a000134
Abstract. Especially in survey research and large-scale assessment there is a growing interest in short scales for the cost-efficient measurement of psychological constructs. However, only relatively few standardized short forms are available for the measurement of cognitive abilities. In this article we point out pitfalls and challenges typically encountered in the construction of cognitive short forms. First we discuss item selection strategies, the analysis of binary response data, the problem of floor and ceiling effects, and issues related to measurement precision and validity. We subsequently illustrate these challenges and how to deal with them based on an empirical example, the development of short forms for the measurement of crystallized intelligence. Scale shortening had only small effects on associations with covariates. Even for an ultra-short six-item scale, a unidimensional measurement model showed excellent fit and yielded acceptable reliability. However, measurement precision on the individual level was very low and the short forms were more likely to produce skewed score distributions in ability-restricted subpopulations. We conclude that short scales may serve as proxies for cognitive abilities in typical research settings, but their use for decisions on the individual level should be discouraged in most cases.