目前使用的智慧型手機普遍地搭載觸控螢幕，然而觸控螢幕過小的按鍵、沒有觸覺回饋的特性均帶來了操作上的種種問題，特別是在虛擬鍵盤的打字操作上，微小化的鍵盤與手指之間的互動衍生了許多人因操作的困難與錯誤。而多重符號鍵盤是過去研究最常使用來改善小按鍵的文字輸入方式，其具有按鍵較大、較少按鍵的鍵盤配置，有利於使用者於觸控螢幕上使用，然而過去的多重符號鍵盤多在嘗試將字母配置、系統預測力最佳化，卻缺乏考量使用者本身的操作經驗、知覺與動作負荷…等因素。因此本研究整理了多重符號鍵盤相關的議題，透過文獻來探討不同的多重符號鍵盤的配置，與設計多重符號鍵盤相關的人因議題，來找出設計多重符號鍵盤的關鍵因素。
本論文之研究階段主要可分為使用者操作姿勢觀察、新式多重符號鍵盤輸入法設計、多重符號鍵盤視覺搜尋以及手部操作實驗、打字績效實驗、以及多重符號鍵盤的使用行為分析。研究結果發現不同的多重符號鍵盤，具有按鍵內字母配置較多者，在視覺搜尋上有較高的負荷，然而以按鍵數與字母數作為預測項之Hick-Hyman law無法有效預測視覺搜尋時間；而在不同的多重符號鍵盤內，平均按鍵尺寸較小的鍵盤具有較高的手部操作負荷，且以鍵盤的困難指數作為預測項之Fitts’ law能有效預測手部操作時間；再者，在不同的多符號鍵盤之間，有著視覺負荷與手部操作負荷的消長關係存在。然而透過打字績效實驗發現，過去的使用經驗確實影響其績效表現，而不同的多重符號鍵盤與不同操作姿勢的組合也會產生不同的績效表現。
本研究成果可作為設計多重符號鍵盤之準則，如按鍵內字母數與視知覺之關係、按鍵大小與操作手部姿勢之相容性，皆可作為未來設計之參考依據。最後，本論文經由研究成果提出未來研究方向，其一為建構更為完整之多重符號鍵盤知覺認知模型，以探究更為具體之打字處理歷程；其二為提出一“適應式使用者介面”概念，希冀能透過感測科技讓行動裝置知曉使用者狀態，進而調整成最適使用者操作之鍵盤介面。

Mobile phone touchscreens have many ergonomic problems related to text entry. Previous studies, which were attempts to use ambiguous keyboards to resolve problems related to small keys, have focused on the disambiguation process without consideration of the user loading on a graphic user interface. This study investigates user loadings, which interfere with performance in the key selection phase when people are using an ambiguous keyboard. Typing efficiency experiment related to the disambiguation phase were also conducted in this study. Hence, three QWERTY-like ambiguous keyboards and a standard QWERTY keyboard were compared via visual search, manual operation and text entry efficiency experiments. The visual search experiment showed that layouts with many letters per key were strongly related to long visual search times, and the Hick-Hyman lay failed to predict users’ performance on ambiguous keyboards. In addition, keyboard layouts with large keys were operated faster and more accurately in the manual operation experiment. In addition, users’ manual performance could be predicting by the Fitts’ law. Consequently, the trade-off between visual and manual loading differed among different letter-key assignments. In addition, the typing efficiency experiment showed the importance of previous typing experience and the compatibility between operating posture and keyboard layouts.
This study is important in that it elucidates the impacts of visual and manual loadings on ambiguous keyboards, as well as the fact that it provides user interface designers with an enhanced understanding of how to design ambiguous keyboards based on user criteria. Meanwhile, future work could build a cognitive model of ambiguous keyboard operation based on the findings of this study, and a new concept of “adaptive user interface” was proposed based on the findings as well.

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