Longer Delays in Rehearsal-based Interfaces Increase Expert Use

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Rehearsal-based interfaces are designed to encourage a transition from novice to expert, but many users fail to make this transition. Most of these interfaces activate novice mode after a short delay, between 150 and 500ms. We investigate the impact of delay time on expert usage and learning in three crowdsourced experiments. The first experiment examines an 8-item marking menu with delay times from 200ms to 2~seconds. Results show longer delays increase successful expert selections. The second and third experiments generalise this result to a different rehearsal-based menu, a desktop clone of FastTap with 8-items and 15-items. Together, our results show that expert use correlates positively with increased delay time, but can increase errors since users are less risk averse. We also find imperceptible delays of 200ms can harm long term retention of menu items. Designers should consider longer delays in rehearsal-based interfaces to encourage a transition to expert usage.