How well does ‚general language proficiency’ explain language test performance?

The current research addresses the seemingly contradiction between the multiple findings of C-tests loading on a single general language proficiency (GLP) factor on the one hand, and the assumption that language proficiency as considered by language testing researchers is multi-dimensional. Research on the structure of language proficiency and in psycholinguistics suggests that GLP may best be represented as the common core across diverse language measures. In the present research, it is hypothesized that C-tests are excellent measures of this common core. In contrast, other language measures, beyond putting demands on GLP, are assumed to tap unique processes, explaining why multi-dimensionality often best reflects the structure of language measures. The current research addresses this hypothesis by examining structural equation models that evaluate alternative assumptions about the dimensionality of language proficiency. 222 students from the highest academic school track in Luxembourg completed a French C-test, as well as the Test de Connaissance du Français (TCF), encompassing measures of reading, listening, speaking and writing. The results show that the four TCF measures put extra demands on unique processes, whereas the C-test measured GLP only. The findings point out that the C-test should not be expected to replace measures of the four basic language skills, i.e., of reading and listening comprehension, or of written and spoken production, when a clear diagnostic of language proficiency in one of those domains is needed.