The efficacy of auditory probes in indexing cognitive workload is dependent on stimulus complexity.

We examined whether the utility of a recently developed auditory probe technique for indexing cognitive workload was dependent on the stimulus properties of the probes. EEG was recorded while participants played a videogame under various levels of cognitive workload. At each level of workload, participants were probed with one of four different types of auditory stimuli: novel complex, repeated complex, novel simple, or repeated simple sounds. Probe efficacy at indexing cognitive workload was assessed by determining which probes elicited ERP components that decreased monotonically as a function of workload. Results suggest that complex auditory stimuli were significantly more effective in indexing cognitive workload than simple stimuli. The efficacy of complex stimuli was due to their ability to elicit a robust orienting response, indexed by the early P3a component of the ERP, which decreased monotonically as a function of cognitive workload.