The paper by Wilson and Moore (this volume), based on the Messick Lecture delivered in 2006 at the annual Language Testing Research Colloquium in Melbourne, may present a familiar challenge to some language testers: of reading outside one's comfort zone. The distinctive character of language testing lies in its combination of two primary fields of expertise: (1) applied linguistics; and (2) measurement. The tradition of the Messick Lecture at the annual Language Testing Research Colloquium (LTRC) has been to invite those with expertise in measurement, often from outside language testing, to share their current work with language testing practitioners. This paper is admirably clear and patient in its setting forth of the logic and detail of the psychometric models it presents, and illustrating these with data from language testing. On a technical note, the paper gives a lucid and practically useful discussion of effect sizes in Rasch analyses, and also helps one to understand the point and the logic of model goodness of fit tests for language test data. It is also important to note that the logic of the approach outlined in the paper is not restricted to Rasch models but applies to non-Rasch models as well, including two-parameter logistic models and multidimensional models. The extensive research effort within language testing to provide empirical support for the practice of content-referencing of language tests has clear implications for the validity of content-referencing more generally, and deserves to be more widely known. It also demonstrates the advantage of ongoing dialogue between subject matter assessment specialists, such as language testers, and psychometricians, of the kind triggered by Wilson and Moore's stimulating paper. (Contains 1 note.)