The Inviscid Text Entry Rate and its Application as a Grand Goal for Mobile Text Entry

Per Ola Kristensson, Keith Vertanen

MobileHCI '14: Proceedings of the ACM International Conference on Human-Computer Interaction with Mobile Devices and Services, 2014.

We introduce the concept of the inviscid text entry rate: the point when the user's creativity is the bottleneck rather than the text entry method. We then apply the inviscid text entry rate to define a grand goal for mobile text entry. Via a proxy measure we estimate the population mean of the sufficiently inviscid entry rate to be 67 wpm. We then compare existing mobile text entry methods against this estimate and find that the vast majority of text entry methods in the literature are substantially slower. This analysis suggests the mobile text entry field needs to focus on methods that can viably approach the inviscid entry rate.