近年來產品可用性的價值迅速增長，不僅是出於商業目的，在某些領域系統的
可用性可能是生死攸關的情況。現有的評估技術包括使用任務分析、可用性測試、 脈絡訪查等已在業界被使用多年，但近來要求更高效率和準確性的評估方式逐漸被 發展以確保快速與穩健的結果。拜市售傳感器的發展所賜，使用性評估利用生理訊 號(bio-signal)和與使用性相關構念的研究逐漸興起。諸如情緒和心理負荷(mental workload)等相關構念已有研究探討其作為衡量可用性的效果。然而，仍有一些對使 用者介面(user interface)和資訊架構(information structure)重要的構念尚未被研究。 本研究旨在透過使用單頻道腦電圖(EEG)設備和眼動追踪(eye-tracking)設備測量使 用者的注意力，了解使用者的注意力在感知可用性中的作用;使用系統可用性量表 (SUS)測量可用性。實驗結果顯示，EEG 注意力值在難度較高的任務中顯著地較高 且較不穩定，但在網站可用性之間沒有顯著差異;而在較難的任務和較低可用性的 網站中，眼動注意力值明顯高於在較簡單的任務與較高的使用性網站中的量測值。 我們試圖了解 EEG 注意力值在網站可用性之間的不顯著性後發現較難任務中的任 務時間明顯比較簡單任務的任務時間長，並且 EEG 注意值在較難任務條件下的網 站可用性之間存在顯著差異。本研究透過上述結果得出 (1) 使用者的注意力在較困 難(在更複雜的任務中和更低的可用性網站)(2) EEG 注意力變項的可行度在具一 定難度與長度的任務中可能會較高 (3) 眼動資料可能比單頻道 EEG 資料更可以預 測使用性分數。本研究為使用性研究開啟了新的視角以及為使用性研究人員提出使
用 EEG 作為使用者注意力相關測量的建議。
關鍵字:網頁使用性、任務難易度、注意力、EEG、眼動追蹤、SUS

The value of product usability has increased, it is not only for business purposes, but in some fields, the usability of the system could also be a life and death situation. Classic evaluating techniques, e.g., task analysis, usability testing, contextual inquiry, etc., have been used by practitioners for years. Yet, industry and academic fields have asked for more efficiency and accuracy to ensure robust results. Usability measurement using physiological response has risen lately due to the development of commercially available sensors, e.g., ECG, HRV, GSR, EEG, eye-tracking, etc. This study evaluates the perceived usability through electroencephalography (EEG) and eye-tracking techniques. According to previous studies, researchers have adopted these two physiological measurements to assess attention for a long time. Attention is a fundamental human cognitive process that helps people to notice, select and process specific information. Users' attention is highly related to a system's interface design and information structure, which correlate with system usability. The results showed the EEG-measured attention level was significantly higher in more complex tasks. Additionally, the standard deviation of EEG-measured attentional level was significantly higher in a more complicated task and the website with lower usability. The number of fixations is significantly higher in more complex tasks and the website with lower usability. Additionally, the number of saccades caused complete opposite results. Furthermore, regression analysis showed that the number of fixations could significantly predict the usability score of websites. Interaction of the average attention occurred when the participants performed the complex task on the website with a lower usability rating. Interaction of the average number of saccades. The results concluded that (a) users' attention may be more focused and more unstable in more complicated situations, and (b) eye-tracking data could better predict perceived usability scores than single-channel EEG data. This study provides a new perspective on website usability.
keywords: website usability, task difficulty, attention, EEG, eye-tracking, SUS

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