Tightly-coupled interaction is shared work in which each person’s actions immediately and continuously influence the actions of others. Tightly-coupled interaction is a hallmark of expert behaviour in face-to-face activity, but becomes extremely difficult to accomplish in distributed groupware. The main cause of this difficulty is network delay – even amounts as small as 100ms – that disrupts people’s ability to synchronize their actions with another person. To reduce the effects of delay on tightly-coupled interaction, I introduce a new technique called Feedback-Feedthrough Synchronization (FFS). FFS causes visual feedback from an action to occur at approximately the same time for both the local and the remote person, preventing one person from getting ahead of the other in the coordinated interaction. I tested the effects of FFS on group performance in several delay conditions, and my study showed that FFS substantially improved users’ performance: accuracy was significantly improved at all levels of delay, and without noticeable increase in perceived effort or frustration. Techniques like FFS that support the requirements of tightly-coupled interaction provide new means for improving the usability of groupware that operates on real-world networks
