Can readability on small screens be improved by using adaptive Rapid Serial Visual Presentation (RSVP) that adapts the presentation speed to the characteristics of the text instead of keeping it fixed? In this paper we introduce Adaptive RSVP, describe the design of a prototype on a mobile device, and report findings from a usability evaluation where the ability to read long and short texts was assessed. In a latin-square balanced repeated-measurement experiment, employing 16 subjects, two variants of Adaptive RSVP were benchmarked against Fixed RSVP and traditional text presentation. For short texts, all RSVP formats increased reading speed by 33% with no significant differences in comprehension or task load. For long texts, no differences were found in reading speed or comprehension, but all RSVP formats increased task load significantly. Nevertheless, Adaptive RSVP decreased task load ratings for most factors compared to Fixed RSVP. Causes, implications, and effects of these findings are discussed.

The proposed ActionMapper tool extends previous work on the generic KeystrokeMapper tool to provide an efficient method of logging and visualising a novice user's interaction with a dynamic interface. For any specified task the ActionMapper could generate a graphic representation of both the designer's conceptual model (represented by an Optimum path) and an indication of the user's mental model (represented by the actual path navigated by the user). In this study, the results from two usability experiments have been analysed using the KeystrokeMapper concept. From this a refined version of the tool, referred to as ActionMapper, is outlined. It is argued that the future implementation of the ActionMapper concept as a computer-based tool, which includes the automatic analysis and visualisation of numerous usability metrics, will substantially enhance the evaluation process. By adding event recording functionality in a prototype for a small handheld device, effective usability evaluations could also be conducted in a mobile context.

In order to assess if productivity based on extrapolated data is a good predictor of longer texts, an experimental study was conducted. Two full-sized text input devices for touch typing and two miniaturized for tapping were used, all featuing QWERTY layout, in a repeated measurement design. Twenty subjects were exposed to both a task within the limit of working memory (nine words) and four running memory tasks (approx. 275 words). For miniaturized tapping keyboards, extrapolated data significantly underestimated both entry speed (uncorrected wpm, up to 17%) and character error rate (up to 61%) whereas it significantly overestimated ratio of correct words (up to 62%) of running memory tasks. Further, error-corrected entry speed was significantly overestimated up to a factor of 2.7. Results based on extrapolated productivity metrics must therefore be interpreted with caution. Running memory tasks with text length of more than 32 words is needed to assess productivity of text input devices if tapping is used.

Using traditional mobile input devices results in decreased effectiveness and efficiency. To improve usability issues a portable Non-Keyboard QWERTY touch-typing paradigm that supports the mobile touch-typing user is presented and investigated. It requires negligible training time. Pressure sensors strapped to the fingertips of gloves detect which finger is depressed. A language model based on lexical and syntactic knowledge transforms the depressed finger stroke sequence into real words and sentences. Different mobile input QWERTY paradigms (miniaturised, floating and Non-Keyboard) have been compared with full-size QWERTY. Among the mobile input paradigms, the Non-Keyboard fared significantly better, both regarding character error rate and subjective ratings.

Two public Swedish telephone voice response information services, using the traditional digit code paradigm for object representation, were implemented using the new auditory AlphaWheel paradigm. The paradigm is a software-implemented direct manipulation interface of the alphabet. Usability was tested experimentally, using the ETSI (European Telecommunications Standards Institute) usability model. Ten naive subjects participated in a test of each service, using both digit code and AlphaWheel paradigms. Some tasks required significantly longer completion time and more keystrokes using the new AlphaWheel paradigm. However, flexibility is high, since the new paradigm does not require access to any (code) manual. 70% of the users preferred the AlphaWheel application. Vocabularies limited to 400 - 500 objects are well suited for the paradigm, since in over 90% of the cases, only 1- 2 of the initial letters of a name have to be elicited in order to generate a suitably constrained output set of objects.