[Design and validation of a computer-based task for the induction of a mental workload spectrum]

As part of the driver's cab 4.0 project funded by the BMBF, an adaptive human-machine interface for agricultural machinery, which detects the current level of mental workload by analysing physiological data is being developed. For this purpose, an experimental task is designed and evaluated, which can induce a mental workload spectrum from little to very strenuous in humans. In three laboratory studies, mental workload is generated by a monitoring activity, with varying difficulty levels. The complexity of the activity is increased by a visual and/or an auditory secondary task. Subjectively perceived mental workload is evaluated by using the Rating Scale Mental Effort, collecting reaction times and error rates. The studies with N = 17, N = 8 and N = 21 participants show that a dynamic combination of main and secondary tasks can induce significantly different degrees of workload (F (2.40) = 54,834, p < 0.001).Practical Relevance: The experimental task developed in this paper will be used to design a measuring system for mental workload based on physiological indicators for combine harvesters. In low-workload situations (e.g. automated harvesting) additional recommendations for action should be proposed by the system. During high workload sections excessive demands on the user should be avoided by only showing the information necessary to carry out the task at hand.