Immediate and delayed after-effects of long lasting mentally demanding work

This study investigates the hypothesis that long lasting mental work demand s are reflected in after-effects on attention demanding post-test probe tas ks. Sixteen subjects were engaged in 2 simulated workdays consisting of men tally demanding tasks. On the difficult day the afternoon consisted of high ly demanding information processing tasks; on the easy day the demands duri ng the afternoon were low. The mornings of both days were equally demanding . At the start (pre-test) and the end (post-test) of both days, after 5 min (immediate post-test) as well as after similar to 2 h of recuperation (del ayed post-test), a probe task was carried out. A memory-search task (varied mapping) is used as probe task. After-effects were expected in terms of a shift in the ratio between performance and effort on the post-test probe ta sks compared with the pre-test probe task. Performance measures were reacti on time and errors; effort was indicated by heart rate variability in the 0 .07-0.14 Hz band, referred to as 0.1 Hz component. Dayload manipulation app eared to be effective because of the load-related differences between the u rinary excretion rates of adrenaline during both afternoons. Compared with the pre-test, only the number of errors was significantly increased in the post-test, carried out immediately at the end of the difficult afternoon. H owever, compared with the easy day, in the delayed post-test probe task aft er the difficult day, subjects tended to shorten reaction times, made signi ficantly more errors, and invested significantly less effort. Moreover, at that time they felt mon fatigued and deactivated as indicated by the result s of the 'Scale of Experienced Load' (SEB) (fatigue) and 'Groninger Adjecti ve Checklist' (GACL) (mood) questionnaires. The observed shift towards low- effort, more 'risky' task strategies in the post-tests fits well with Hocke y's (1993) fatigue after-effects degradation pattern expected after periods of high workload. The repeated measurement of the relation of performance, effort and feelings reveals the dynamics of the pattern of fatigue after-e ffects over the (recovery) time. (C) 2000 Elsevier Science B.V. All rights reserved.