Disambiguating Complexity: From CAF to CAFIC: A Commentary on “Complexity and Difficulty in Second Language Acquisition: A Theoretical and Methodological Overview”

In their position paper, Complexity and Difficulty in Second Language Acquisition: A Theoretical and Methodological Overview, the authors propose to reserve the term "complexity" for absolute structural complexity and "difficulty" for other typically called "complexity" measures in the Complexity-Accuracy-Fluency (CAF) triad. We agree with the authors that there are excellent arguments to make these distinctions and that we should avoid "conceptual ambiguity of the key notions and the proliferation of measures, with little attention to issues such as their construct validity and redundancy" (p. 2). At the end the authors suggest adding two new constructs to the triad: difficulty (the ability to comprehend and produce difficult linguistic structures) and appropriateness (the ability to choose within one’s repertoire the alternatives that are most adequate for a given communicative context), so that the acronym may become CAFDA. We agree that it might be useful to add new constructs, but not only are "difficulty" and "adequacy" difficult to operationalize in terms of quantifiable linguistic feature, but more importantly, they do not do justice to many new useful measures that have emerged over the last decades that need to be subsumed under separate constructs.