The Paced Serial Addition Test (PSAT) presents a series of digits at different speeds with the requirement that the two most recent numbers be added together. Although the PSAT is a relatively difficult test, its level of difficulty may be decreased by changing the number list to make the answers simpler and by presenting the digits visually rather than aurally. In view of this, the present experiment varied both task difficulty (easy vs. hard) and mode of presentation (visual vs. auditory). Task difficulty was manipulated by using two different lists composed of single digits whose answers ranged between 2 and 10 (easy) or 2 and 18 (hard). All stimuli were presented by computer which permitted measurement of response latencies, as well as correctness of responding. The results showed that mode of presentation, but not task difficulty, produced highly significant effects. Additional evidence showed that the ability to compute answers to simple addition problems must be considered as a modulator variable. However, an individual’s basic arithmetic ability is not as critical as the modality in which a stimulus is presented. The lower performance associated with the auditory version (i.e., PASAT) was interpreted as an interference effect caused by both the stimulus and the response occurring in a single auditory information processing channel. This interpretation suggests that the PASAT’s well documented sensitivity to traumatic brain injury (TBI) may be due, at least in part, to an increased susceptibility to interference effects rather than attributable solely to a decreased rate of information processing.

A modified computer version of the PASAT (Adjusting-PSAT; ) is described that measures speed of information processing and working memory by means of a temporal threshold rather than number of correct responses. This is accomplished by making the duration of the interval between numbers depend on the correctness of responding-a correct response decreases the interval between digits and an incorrect response increases the interval. Modality of presentation (visual and auditory) was factorially combined with problem difficulty (answers between 2-10 or 2-18). Performance of 60 healthy student volunteers on the Adjusting-PSAT was compared to that obtained on several traditional neuropsychological measures (Digit Span, Trail Making Test, and Symbol Digit Modality Test) and on a test of basic addition skills. The visual version of the test produced a lower threshold than did the auditory version, but problem difficulty did not produce a significant effect. Of the neuropsychological tests, Trails-B (TMT-B) was most highly correlated with thresholds. However, regression analyses revealed that math ability accounted for more variance than did TMT-B. The clinical implications of these finding are discussed.

Normative data stratified by three levels of age (16–59, 60–79, and 80–95 years) and three levels of education (0–8, 9–12, and 13–21 years) are presented for phonemic verbal fluency (FAS) and categorical verbal fluency (Animal Naming). The normative sample, aged 16 to 95 years, consisted of 1,300 cognitively intact individuals who resided in the community. Years of education ranged from 0 to 21. The total number of words in 1 minute for each of the letters F, A, and S was correlated r = .52 with the number of animal names generated in 1 minute. Regression analyses showed that FAS was more sensitive to the effects of education (18.6% of the variance) than age (11.0% of the variance). The opposite relationship occurred for Animal Naming, where age accounted for 23.4% of the variance and education accounted only for 13.6%. Gender accounted for less than 1% of variance for FAS and Animal Naming. The clinical utility of these norms is discussed.