Standardization and adult norms for the sequential subtracting tasks of serial 3's and 7's.

The Serial 3's and 7's subtraction tasks are traditionally used in mental status examinations. The usefulness of these tasks is based upon the assumption that they measure attention and mental concentration. However, there is no uniform method of administration, and there are no recognized norms for these subtraction tasks, which has led some in the field of psychiatry and neuropsychology to conclude that the tests are not useful. The purpose of this research had three goals: (a) to create a standardization of the administration, (b) to provide a structured and consistent framework for the data evaluation, and (c) to create adult norms as a frame of reference for interpretation. The study investigated normal control subjects (N = 204) and specific variables of interest included both efficiency and accuracy of performance. The results demonstrated that when used conjointly, Serial 3's and Serial 7's are an efficient and accurate measure of sequential subtracting, but even more importantly, the study revealed the hierarchical increase in cognitive demand when the performances between 3's and 7's were compared. With standardization and norms, serial subtraction becomes a more effective screening technique within the context of a mental status examination. Similarly, the conjoint administration of these tasks yields synergistic data that can be useful in determining deficits in the cognitive domains of attention and working memory.