Assessing Usability for Input Operation using Frequency Components of Eye Movements

Dynamic usability-testing is required for the improvement of various Human-Computer interactive systems. This paper examines the indices of assessing usability using the frequency spectrum of eyemovements up to four Hz. An input operational task experiment was conducted using a mouse (Mouse), a keyboard (KeyBD) and a keypad (KeyPAD), and the conventional subjective system usability measurements (SU-scores) and error rates were measured. Most power spectrum densities (PSD) for eyemovements in the first second of the experiment followed the same order of the SU-scores or error rates. Cross spectrum densities (CSD) between horizontal and vertical eye-movements and coherence as standardized CSD also significantly correlate with the results of the SU-scores and error rates. To determine the frequency range of CSD and coherence for usability assessment, frequency components used as factors were extracted using factor analysis. According to the correlation coefficients between these and the performance of factor scores for predicting the conventional metrics, factor scores of CSD can be better indices for assessing usability than can indices of coherence.