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Abstract

The extent to which we experience ‚workload‘ whilst steering depends on (i) the availability of the human operator’s (presumably limited) resources and, (ii) the demands of the steering task. Typically, an increased demand of the steering task for a specific resource can be inferred from how steering modifies the components of the event-related potential (ERP), which is elicited by the stimuli of a competing task. Recent studies have demonstrated that this approach can continue to be applied even when the stimuli does not require an explicit response. Under certain circumstances, workload levels in the primary task can influence the ERPs that are elicited by task-irrelevant target events, in particular complex environmental sounds. Using this approach, the current study assesses the human operator’s resources that are demanded by different aspects of the steering task. To enable future studies to focus their analysis, we identify ERP components and electrodes that are relevant to steering demands, using mass univariate analysis. Additionally we compare the effectiveness of sound stimuli that are conventionally employed to elicit ERPs for assessing workload, namely pure-tone oddballs and environmental sounds. In the current experiment, participants performed a compensatory tracking task that required them to align a continuously perturbed target line to a stationary reference line. Task difficulty was manipulated either by varying the bandwidth of the disturbance or by varying the complexity of the controller dynamics of the steering system. Both manipulations presented two levels of difficulty (‚Easy‘ and ‚Hard‘), which could be contrasted to a baseline ‘View only’ condition. During the steering task, task-irrelevant sounds were presented to elicit ERPs: frequent pure-tone standards, rare pure-tone oddballs and rare environmental sounds. Our results show that steering task demands influence ERP components that are suggested by the previous literature to be related to the following cognitive processes, namely the call for orientation (i.e., early P3a), the orientation of attention (i.e., late P3a), and the semantic processing of the task-irrelevant sound stimuli (i.e., N400). The early P3 was decreased in the frontocentral electrodes, the late P3 centrally and the N400 centrally and over the left hemisphere. Single subject analyses on these identified components reveal differences that correspond to our manipulations of steering difficulty. More participants discriminate for above components in the ‘Hard’ relative to the ‘Easy’ condition. The current study identifies the spatial and temporal distribution of ERPs that ought to be targeted for future investigations of the influence of steering on workload. In addition, the use of task-irrelevant environmental sounds to elicit ERP indices for workload holds several advantages over conventional beep tones, especially in the operational context. Finally, the current findings indicate the involvement of cognitive processes in steering, which is typically viewed as being a predominantly visuo-motor task.