No abstract

Vigilance performance has become an important factor in modern work. In a previous publication, we presented a test for screening visual vigilance performance and satisfying practical requirements of occupational medicine, such as an ecologic valid test setting, a short duration of testing, a test designed for detecting weak performers and offering comparative vigilance performance data (N=150) of the normal population. The test requires an observer to detect the digit "3" in a six-digit number, which is flashed over a distracting video background. From collected answers, the vigilance performance is computed by means of the theory of signal detection and for three different locations of the six-digit number in the visual field, which are on the left, in the center, and on the right visual field. After a series of successful applications of the test in many different circumstances, various interests from research and practice arose, wishing to expand the test in order to assess vigilance performance in high performing observers. In order to accommodate this demand, the level of difficulty of our vigilance test was increased. This was achieved by shortening the exposure duration of the target presented in the vigilance test from originally 300 ms down to 200 ms. In the here presented study, an experiment is reported, aiming to establish comparative data of the normal population taking the vigilance test at the higher and at the lower (original) level of difficulty as well. Since vigilance performance is affected by age and the top performers have been found to be younger than about 40 y, a population of 60 observers ranging between 19 y and 40 y was used in the experiment. In half of the population, the shorter exposure time of the target was administered first. Statistical analysis of vigilance performance clearly showed an effect of exposure time. When shortening the target exposure time from 300 ms to 200 ms, the average sensitivity d' drop from 2.7 (SD=0.9) to 1.2 (SD=1.2). The number of times at which peak values for d' were recorded was reduced when shortening the exposure time of the target. A reduction of the number of peak records appeared for targets presented in the central visual field (from 19 times down to 7 times when shortening the exposure time from 300 ms to 200 ms) as well as for targets presented in the peripheral visual field (from 7 times to 0 times). Given above described results, we conclude that reducing the exposure time of the target in the test for assessing vigilance performance from 300 ms to 200 ms, the difficulty of the vigilance test could be significantly increased. Therefore, the test appears more adequate to be used for testing people trained for high stress, such as surgeons. With the improved test we plan to investigate the effectiveness of ergonomic improvements in workplaces at which workers are exposed to a high level of stress. Among such measures are the management of rests, strategies of work and system optimizations in general..