ABSTRACT
In recent years, usability evaluations have evolved into comprehensive assessments that combine objective metrics and subjective evaluations. It has been shown that the prefrontal cortex is responsible for higher brain functions such as cognition, judgment, and attention. Activation of the prefrontal cortex during use of a product can therefore be regarded as an indicator of the amount of executive function required for product use, and is considered a measure of usability. In the present study, we used functional near-infrared spectroscopy (fNIRS) to measure hemodynamic changes in the prefrontal cortex during performance of repetitive mousing tasks on a computer. The usability of these tasks was varied by adjusting the difficulty of the task. We evaluated the effects of usability on brain activity on oxygenated hemoglobin (oxyHb) levels in the prefrontal cortex and dorsolateral area 46. Eleven participants (9 male, 2 female) completed a click mousing task and a drag mousing task on two separate days. We quantified the overall change in oxyHb (δoxyHb) levels during task performance. Positive δoxyHb values indicate an overall increase in oxyHb levels across the duration of the task, whereas negative 260δoxyHb values indicate an overall decrease in oxyHb levels. We found negative δoxyHb values in drag mousing tasks with the largest target size, indicating that oxyHb levels decreased during the best-quality usability task. We found positive δoxyHb values in other usability tasks. Additionally, δoxyHb values tended to increase when the usability deteriorated. These results suggest that fNIRS may be useful in usability evaluations.
