The writing superiority effect: Language production processes in the verbal diagnosis of knowledge

Language production processes are frequently involved in the diagnosis of knowledge, particulary with exams. However, the relation between the cognitive knowledge basis and the spoken or written output is seldomly addressed. We investigated whether and how processes of language production related to speaking and writing systematically influence the results of verbal diagnoses of knowledge. Particularly, the writing superiority effect turned out to be a stable and replicable finding: In adults, writing allows for higher content validity of the indication of knowledge, compared to speaking. A theoretical analysis of the oral and written language production processes and the related cognitive load through its particular subprocesses explains why linguistic output generally does not provide a valid window to cognition. For the diagnosis of knowledge, the advantage of writing as opposed to speaking is experimentally demonstrated. In subsequent experiments, working memory capacity as well as the correspondence between the verbal modalities of knowledge input and output prove and arousal seem to to be determining factors of the writing superiority effect, whereas verbal intelligence as well as stress exert no influence.