Can readability on small screens be improved by using Rapid Serial Visual Presentation (RSVP) that adapts the presentation speed to characteristics found in the text? In this thesis Adaptive RSVP is introduced together with two algorithms for adaptation. Findings from a usability evaluation, where the ability to read long and short texts on a mobile device in a realistic setting was assessed, are reported. In a balanced repeated-measurement experiment employing 16 subjects two variants of Adaptive RSVP were benchmarked against Fixed RSVP and traditional text presentation. No significant differences were found for reading speed and comprehension for long texts but for short texts all RSVP formats increased reading speed by 33%. For long texts Adaptive RSVP decreased task load compared to Fixed RSVP and repeated use of RSVP, regardless of type, was also found to decrease task load. No differences in task load were however found for short texts. Causes, implications and effects of these findings are discussed together with directions for further work. ii Acknowledgements The author would foremost like to thank Mikael Goldstein for inspiration, supervision and a lot of support during the work with this thesis. Many thanks also to Peter Ljungstrand and Staffan Bjrk at the Interactive Institute for valuable collaboration. The author would also like to express gratitude to all colleagues at Ericsson Research's Usability & Interaction Lab in Stockholm and Sony Ericsson Mobile Communications in Lund. Much credit is also awarded all of those who participated in the usability evaluation. Last but not least, the author would like to put across many thanks to family and friends for love and support. iii Table of Contents Abstract.....................................................

The thesis presents findings from five readability studies performed on mobile devices. The dynamic Rapid Serial Visual Presentation (RSVP) format has been enhanced with regard to linguistic adaptation and segmentation as well as eye movement modeling. The novel formats have been evaluated against other common presentation formats including Paging, Scrolling, and Leading in latin-square balanced repeated-measurement studies with 12-16 subjects. Apart from monitoring Reading speed, Comprehension, and Task load (NASA-TLX), Eye movement tracking has been used to learn more about how the presentation formats affects reading. The Page format generally offered best readability. Reading on a mobile phone decreased reading speed by 10 % compared to reading on a Personal Digital Assistant (PDA), an interesting finding given that the display area of the mobile phone was 50 % smaller. Scrolling, the most commonly used presentation format on mobile devices today, proved inferior to both Paging and RSVP. Leading, the most widely known dynamic format, caused very unnatural eye movements for reading. This seems to have increased task load, but not affected reading speed to a similar extent. The RSVP format displaying one word at time was found to reduce