The Visual Span in Reading in Additive Augmented Displays: Similarities and Differences to/with a Typical Computer Display

Arda Fidanci¹, Minjung Kim³, Xiuyun Wu², Trisha Lian², Saeideh Ghahghaei Nezamabadi²; ¹University of Minnesota, ²Meta Platforms, INC., CA, United States, ³Independent Researcher

The visual span in reading, the number of letters recognized in a single fixation, is a key sensory bottleneck and a predictor of reading speed on computer displays (CD). Additive augmented reality (AR) displays introduce unique optical properties that may affect the processing of the text and reading performance. We measured the visual span in AR and CD. Nine participants with typical vision were recruited. The visual span was assessed via a letter recognition task: participants briefly viewed trigrams (75 ms) at 11 letter positions (at fixation or up to 5 letters to the left/right), and reported the letters after each trial. Letter accuracy was calculated for each letter position. AR: We simulated AR using a Haploscope with see-through mirrors, with the text’s viewing distance at 117 cm. The background was a plain grey or 1/f pattern (mean of 70 nits) at 3m viewing distance. The light in AR is additive, so the contrast was calculated as 1 + (text max luminance) / (background luminance). Four additive contrast levels (1.25, 1.6, 2, 3) and two backgrounds (1/f noise and plain) were tested. CD: Participants completed a standard visual span test with white text on a grey background at 117cm viewing distance (contrast of 3). Results: The visual span size was larger in AR than in CD (p<0.001), and was less asymmetric. In AR, the visual span expanded with additive contrast (p < 0.001), and was marginally larger for plain than 1/f background (p = 0.07). Conclusion: The results indicate that media can impact the visual span size and shape: a larger span in AR than CD. Contrast remains a major contributor to the visual span in AR, and background seems to impact the visual span.

Acknowledgements: This work has been funded by META Platforms INC. The study has been conducted at META as part of first author's internship.