Is 100 Milliseconds Too Fast?

Abstract

For years, software engineers have been told that applications must respond to user events within 100 milliseconds to seem instantaneous, yet this assumption has never been systematically tested. In this research, we attempt to establish thresholds of detection for changes in a graphical user interface using adaptive tracking. For keyboard interactions, subjects did not notice delays of approximately 150 milliseconds. In contrast, for mouse interactions, subjects did not notice delays of up to 195 milliseconds. Given these findings, further research is clearly needed to firmly establish lower bounds on application responsiveness so that software and operating system engineers can more precisely tune the interactive real-time responsiveness of their systems.