The effects of mild and severe traumatic brain injury on the auditory and visual versions of the Adjusting-Paced Serial Addition Test (Adjusting-PSAT)

Auditory and visual versions of the Adjusting-PSAT [Tombaugh, T. N. (1999). Administrative manual for the adjusting-paced serial addition test (Adjusting-PSAT). Ottawa, Ontario: Carleton University] were used to examine the effects of mild and severe traumatic brain injury (TBI) on information processing. The Adjusting-PSAT, a computerized modification of the original PASAT [Gronwall, D., & Sampson, H. (1974). The psychological effects of concussion. Auckland, New Zealand: Auckland University Press], systematically varied the inter-stimulus interval (ISI) by making the duration of the ISI contingent on the correctness of the response. This procedure permitted calculation of a temporal threshold measure that represented the fastest speed of digit presentation at which a person was able to process the information and provide the correct answer. Threshold values progressively declined as a function of the severity of TBI with visual thresholds significantly lower than auditory thresholds. The major importance of the current study is that the threshold measure offers a potentially more precise way of evaluating how TBI affects cognitive functioning than is achieved using the traditional PASAT and the number of correct responses. The Adjusting-PSAT offers the additional clinical advantages of eliminating the need to make a priori decisions about what ISI should be used in different clinical applications, and avoiding spuriously high levels of performance that occur when an "alternate answer" or chunking strategy is used. Unfortunately, the Adjusting-PSAT did not reduce the high level of frustration previously associated with the traditional PASAT.