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Four-Key Text Entry for Physically Challenged People

For physically challenged people, learning of typing skills is essential, especially for those who are undertaking courses of study. Current user interfaces are well designed to assist an ordinary user in producing fast output and allowing customization, but can be complicated for an impaired user. The challenge is to find an efficient textual input technique making use of a small number of fingers, keys and minimal resources of the residual visual acuity. Researchers have experimented with alternative methods allowing text entry with less than four keystrokes per character using three keys. Nevertheless, the proposed strategies require strong visual and cognitive support. In this paper we describe a four-key text entry technique with three keystrokes per character. A finger memory provides complementary help and follows the style of the interaction in a natural way. We have applied the symmetric hierarchical structure with 3 levels and 4-2-4 alternatives, as the basic layout for symbol input and imaging. This method resulted in entry rate of 15 wpm. The experimental results showed that the proposed approach significantly decreases cognitive load and facilitates navigation through continuous sequence of automatic actions.