Digit Ordering Test: clinical, psychometric, and experimental evaluation of a verbal working memory test.

Cooper, Sagar, Jordan, Harvey, and Sullivan (1991) proposed a Digit Ordering Test (DOT) for the assessment of verbal working memory: A series of seven digits has to be memorized and immediately recalled in ascending order. In several studies Cooper and co-workers showed selectively reduced DOT performance in patients with Parkinson's disease (PD). We present results from three studies on the properties of this test. In study 1 we replicated the original findings and evaluated a new scoring method. Study 2 addressed the psychometric features of the DOT and provides normative data based on a total of 134 test protocols (PD: 18, other neurological patients: 60, healthy controls: 56). In study 3 we used an experimental modification of the test (DOT-EXP) to evaluate the effects of the presentation rate on serial recall and digit ordering performance. The standard presentation rate of seven digits in 5 s was confirmed as most sensitive for detection of verbal working memory deficits. Findings confirmed that the DOT addresses the manipulatory component of verbal working memory and conveniently detects respective deficits in clinical testing.