It is not clear which of the R-E and the S-R compatibility principles is proper for the eye-gaze input. This issue should be addressed for the development of more usable eye-gaze input system. The aim of this study was to explore which of the two compatibility principles was proper for the eye-gaze input system. For all scroll methods, the task completion time did not differ between R-E and S-R compatibility conditions (see Fig. 4). In other words, the speed of scroll did not differ between two compatibility conditions for all of three scroll methods. The number of errors per 90 trials significantly differed among scroll conditions and between R-E and S-R compatibility conditions. Judging from the accuracy of scroll, the error was less when the S-R compatibility like non-touch screen Microsoft Windows was applied than when the R-E compatibility like iPod or iPad was applied. In the range of this study, it seems that the S-R compatibility is dominant from the viewpoints of scroll accuracy for all of three scroll methods. The subjective rating on both usability and fatigue also supported the superiority of S-R compatibility over the R-E compatibility condition. In conclusion, the S-R compatibility was found to be superior for the eye-gaze input system.