How Normal Are Normal Errors of Language and Cognition?

Purpose: The aim of this study was to estimate the frequency and severity of common errors and inefficiencies of language and cognition in the general population. Method: Item-response theory parameters were analyzed from the Neuro-QOL Cognitive Function Item Bank v2.0, which references a large normative sample that mirrors the demographics of the U.S. Census. Item parameters were analyzed to reveal the most likely responses to items about errors and inefficiencies of language and cognition. These most likely responses were estimated for each of 25 levels of theta to reveal normal and gradations of abnormal experiences of errors and inefficiencies. Results: A typical experience with language and cognitive errors and inefficiencies (e.g., producing a T score between 40 and 60) is to have a little difficulty with each task that was assessed or to experience nearly every error/inefficiency at least once a week. Word-finding effort was particularly ubiquitous, as was the experience of walking into a room and forgetting one's intention. Conclusions: It is typical to experience errors and inefficiencies of language and cognition. This analysis describes a typical experience for an average person in a highly representative sample. However, more work is needed in order to learn what is typical for more specific subgroups, for example, based on age.