A series of experiments were performed with the aim of looking into possible differences of the effects of task difficulty and pacing on some psychophysiological variables in subjects with a low and high level of anxiety. Two equivalent groups of nine subjects (except in anxiety level) performed computer generated numerical and perceptual tasks, where the numerical task had five different difficulty levels, while the perceptual tasks had three. Each of these were perfoemed by every subject under self-paced (unpaced) and paced working conditions. The levels of pacing were equal to the subject's unpaced working level, and 15% higher. The experimental situations were rotated according to the Latin Square principles. During the work on these (primary) tasks, the subject had to perform tapping as the secondary task. Their R-R intervals (sinus arrhythmia) were recorded continuously, together with the tapping intervals. After the completion of the task, the subjects wereasked to estimate the task difficulty on Borg's scale, and to assess it by squeezing a hand dynamometer without looking at its scale. The results showed some differences in the magnitude of certain psychophysiological parameters within the groups, which could be attributed to the effects of task difficulty and pacing. The work-load assessment parameters indicated, that the high anxiety group experienced the tasks and pacing as more strainous, than the low anxiety group. This is especilly true when estimations with a higher mental involvement had to be made. Secondary tasks parameters, however, indicated a smaller residual mental capacity in the group with high anxiety subjects which could represent an explanation of the results on the workload assessment.
