The role of visual search in the design of effective soft keyboards

As portable, handheld computing devices become more common, alternatives to traditional keyboards must be explored. These alternatives must be compact , lightweight and sufficiently efficient to support the users' tasks. One a lternative is the use of small physical keyboards or soft keyboards present ed on touch-sensitive surfaces. Many alternative layouts have been explored , including the QWERTY, Dvorak, telephone and various alphabetic organizati ons. Soukoreff and MacKenzie proposed a model to predict typing times for a lternative layouts, but have experienced limited success matching their pre dictions to observed performance. This paper proposes a revision of the vis ual search component of their model that considers the familiarity of the o rganization and the number of letters represented by each key. Results are reported of an experiment that supports the claim that both familiarity and the number of letters per key must be considered when predicting visual se arch times for alternative keyboard layouts.