Physiological correlates of mental effort as manipulated through lane width during simulated driving.

Previous studies suggest that physiological effects of mental effort as manipulated trough cognitive task difficulty differ from effects of mental effort as manipulated trough a visuomotor task such as lane keeping in simulated driving. Most notably, heart rate increases with mental effort in the former but not in the latter task. EEG seems to be indicative of mental effort in both cases. In previous research [1], Brouwer and colleagues examined effects of mental effort as manipulated in a cognitive (memory) task on a range of physiological signals. In the present research we examine the same types of physiological signals using the same kind of analysis in a visuomotor (simulated driving) task. In this case, mental effort was manipulated using wide and narrow lanes. Effects of task difficulty on both subjective mental effort and behavioral variables were comparable across tasks. Effect of task difficulty was replicated for respiration frequency and to some extent for EEG alpha activity. However, in contrast to the cognitive task [1], skin conductance and heart rate related variables were not significantly affected by task difficulty in the current visuomotor task. We argue that differences in visual attention and cerebral energy demand between the types of tasks may be at the basis of this.