Under pressure : cognitive effort during website-based task performance is associated with pupil size, visual exploration, and users’ intention to recommend

We aimed to validate objective usability methods to measure cognitive workload continuously that could complement traditional methods such as the NASA-TLX scale. To achieve this goal, we investigated advanced eye-tracking (ET) indices of cognitive effort and visual exploration (i.e., pupil size and exploration coefficient K) in a realistic website-based task. We experimentally varied time pressure to test the effect of momentary cognitive effort on these metrics. We found that our ET metrics covaried with NASA-TLX scores and they responded to our time pressure manipulation. Moreover, we showed that visual search became more exploratory under time pressure, which supports current theory in neuroscience that links behavioural exploration, task performance, and arousal. Our study thus applied fundamental research from cognitive neuroscience to the domain of usability testing and showed that advanced ET metrics can be useful tools for usability research