exploring effects of speed and font size with rsvp - CiteSeerX

PROCEEDINGS of the HUMAN FACTORS AND ERGONIMICS SOCIETY 45th ANNUAL MEETING - 2001

EXPLORING EFFECTS OF SPEED AND FONT SIZE WITH RSVP Mark C. Russell and Barbara S. Chaparro Software Usability Research Laboratory Department of Psychology Wichita State University Wichita, Kansas 67260-0034

As electronic devices such as Personal Digital Assistants (PDA), cellular phones and pagers become daily tools for viewing e-mail, news, and websites, the need for new methods of reading text on small screen interfaces increases. Recent studies have demonstrated Rapid Serial Visual Presentation (RSVP) to be a viable method of presenting text on small screens. This study examined the effects of three font sizes (12, 20, & 28-point) and two presentation rates on reading comprehension of text presented in RSVP. Results showed significantly higher reading comprehension for text presented at 250 wpm compared to 650 wpm. No effect of font size was found for reading comprehension, but participants preferred the 20-point font size compared to the 12-point font size. INTRODUCTION Electronic devices such as cellular telephones, digital pagers, and Personal Digital Assistants (PDA’s) are in great demand due to their small size and versatility. A serious limitation, however, is the small amount of space these devices have available for the display of text. As a result, questions arise as to the best way to present text in small electronic windows so that both reading performance and user satisfaction are optimized. Specific considerations include the method of presenting the text, the speed at which the text is presented, and the size of the text. Several text presentation methods have been developed as alternatives to the traditional booklike page. Two examples include presenting text continuously from the bottom of the screen by lines (‘scrolling’) or from the right to left continuously along a single line (‘leading’). Both methods have been shown to be generally less effective in reading speed and comprehension than a traditional page format (for scrolling see Kolers, Duchnicky and Ferguson, 1981; for ‘leading’ see Granaas, McKay, Laham, Hurt and

Juola, 1984; Sekey and Tietz, 1982). Another text presentation method is known as Rapid Serial Visual Presentation (RSVP). As the name suggests, RSVP serially presents text one word at a time in rapid succession in the same area of a screen. Initially, the RSVP method promised to be a means of increasing reading speed by eliminating the need to make eye movements (Rubin & Turano, 1992). Research with RSVP has shown that reading rates and comprehension scores with this method are similar to those found with both sentence-bysentence and normal page methods (Rahman & Muter, 1999). For example, Juola, Ward, and McNamara (1982) tested the readability of text represented in the RSVP method. Subjects read short paragraphs with overall presentation rates ranging from about 200 to 700 wpm. They consistently found comprehension performance was no more reliable with the standard page method than with RSVP. With small screen interfaces, a normal page method is not feasible. The task, therefore, becomes finding an alternative to the normal page format that results in comparable performance. Juola, J. F., Tiritoglu, A., &

PROCEEDINGS of the HUMAN FACTORS AND ERGONIMICS SOCIETY 45th ANNUAL MEETING - 2001

Pleunis, J. (1995), compared RSVP to the ‘leading’ text format and found RSVP to result in higher reading accuracy. Another issue to consider when displaying text on small screen interfaces is whether the progression though text should be controlled by the reader or presented at a set rate. Research has shown that self-paced or manual scrolling of text in electronic windows tends to produce poorer reading comprehension than automatic presentation methods (Chen & Chan, 1990). With regard to RSVP in particular, Muter et al. (1988) tested RSVP with regression—the ability to review text previously presented—in several experiments and initially concluded that permitting reader control in RSVP was feasible but could actually result in slower reading speeds (Muter et al., 1988). In a later study, however, Rahman and Muter (1999) found that an RSVP method with self-pacing and regression was as efficient as a traditional page-like format, though not a sentence-by-sentence presentation method. With regard to the size of the text, it has been found that reading speed tends to improve with an increase in text size up to a critical point (called the maximum reading speed), after which the effect levels off (Legge, Pelli, & Schleske, 1985. The range of possible text sizes on devices with small screens is limited, therefore we hypothesized that there might still be an observable effect by character size on reading performance. Overall, there appears to be evidence to support the proposition that RSVP is a viable option when considering its use as a text presentation method on devices with small screens. In a previous study, Bernard, Chaparro and Russell (2000) found no reading performance differences between RSVP and two other automatic text presentation methods (ten lines or three lines of text at a time), though reading comprehension decreased as the rate of text presentation increased from 250 wpm to 650 wpm. This study investigated the effects of presentation rate and text size on reading comprehension of text passages presented with

RSVP. It was hypothesized that larger text fonts would be easier to read at faster speeds than smaller fonts. In addition, it was hypothesized that readers would be more satisfied with larger fonts at faster speeds than smaller fonts. METHODS Participants/ Materials

Fifteen volunteers (6 men and 9 women between the ages of 18 and 52) participated in this study. Testing was done on a Pentium II class computer, with all text material displayed on a 1024 x 768 resolution 17” color monitor. Ace Reader ProTM [1] was used to present the text in RSVP method and to administer the comprehension test questions. The text passages were provided by the Ace Reader ProTM application and ranged from 127 to 269 (M = 204) words. The passages were generally fictional material in the form of very short stories or as excerpts from larger works. Procedure

Text was presented in a black on light gray format, in an attempt to roughly simulate the background of the average PDA screen. The obvious preference would have been to use an RSVP application on an actual hand-held device such as a PDA, or at the very least a PDA and an emulator program. However, at the time of this study, no such program was available. The manipulated variables in this study were: (1) Arial font sizes of 12, 20, and 28-point; and (2) the rate of automated text presentation, either 250 wpm (considered average reading speed in traditional paper format) or 650 wpm. The font sizes were chosen to represent a wide range of sizes that could be displayed on a typical PDA. The presentation rates chosen were the two speeds between which a significant difference in performance was observed in the previous study (Bernard et al., 2000). The order of the text passages were randomized and the font sizes and

PROCEEDINGS of the HUMAN FACTORS AND ERGONIMICS SOCIETY 45th ANNUAL MEETING - 2001

presentation rates were counterbalanced, with each participant being presented three passages under each of six possible conditions. Of the 23 total text passages read by participants, five were considered practice, due to the novelty of the presentation method, and eighteen were scored. Participants were seated in front of the computer at approximately the same distance of 12”, accounting for individual height, etc. After completing a consent form and a background questionnaire, participants were shown each of the five practice passages and question sets. Each participant was given the same five practice passages in the same order, with each passage being presented at a faster reading speed than the last, from 250 to 350, 450, 550 and 650 words per minute, in order to give the participants experience with changes being made in the presentation rates. After practice was complete, participants read the 18 test passages in various font sizes and at various rates of speed, and completed the related multiple-choice questions for each passage as they progressed. After each condition, participants were asked to complete a Satisfaction Questionnaire with regard to the font size and presentation rate. Once testing was complete under all six conditions, the participants completed a Post-Experiment Questionnaire, to assess overall preferences for font size and presentation rate. RESULTS Reading Comprehension The results of a 2 x 3 (speed by font size) repeated-measures analysis of variance showed a significant main effect for presentation rate [F(1,14) = 40.574, p. < .001]. Participants demonstrated higher comprehension for text presented at 250 wpm than for text presented at 650 wpm see Figure 1). No significant main effect of font size or a speed by font size

interaction was found. In other words, the font sizes used in this study did not affect reading comprehension at either speed.

250wpm

90 80 70 60 50 40 30 20 10 0 12 pt. Font

650wpm

20 pt. Font

28 pt. Font

Figure 1. Reading Comprehension (% correct) scores by Presentation Rate and Font Size User Satisfaction Participants were asked to rate their satisfaction of each presentation condition (speed x font). Analyses of variance of these responses yielded significant main effects for presentation rate on the issues of ease of reading, ability to concentrate, level of confusion, confidence of comprehension, level of eyestrain, and overall comfort level. Basically, participants were more satisfied reading the text passages, at any font size, at the slower speed. The only main effect on these measures of satisfaction for font size was found on the topic of eyestrain, where participants reported significantly more eyestrain with the small (12 pt) font compared to the large (28 pt) font (F (2, 28) = 5.483, p. < .05). Font Preferences Participants ranked the three font sizes in order of preference. A Friedman test was performed on these rankings (see Figure 2), and post hoc tests reveal revealed that the participants significantly preferred the medium font (20 pt) over the small (12 pt) font [χ2(2) = 8.93, p < .05].

PROCEEDINGS of the HUMAN FACTORS AND ERGONIMICS SOCIETY 45th ANNUAL MEETING - 2001 3

REFERENCES

2.5

AceReader Pro Copyright © 1995-2000, StepWare, Inc. All rights reserved. StepWare and AceReader Pro are registered trademarks of StepWare, Inc.

2 1.5 1

12 pt. Font

20 pt. Font

28 pt. Font

Figure 2. Ranked Preference of Font Sizes. (The lower the bar, the more preferred the font) DISCUSSION This study examined the effects of speed and font size on reading comprehension and satisfaction using RSVP. Results indicated an effect of speed, with reading comprehension decreasing as the presentation rate increased. This finding was anticipated and confirms the results of the Bernard et al. (2000) study. What was of greater interest, however, was the finding that font size in this experiment had no effect on reading comprehension. This suggests that RSVP is a resilient format capable of supporting a range of text sizes on small electronic screens. Although there was no effect on performance, participants did indicate a significant preference for the medium size text (20-point) compared to the smaller (12-point) text presented at slower speeds (250 wpm compared to 650 wpm). In general, participants reported greater satisfaction reading text at any font size at the slower speed. One limitation of this study is how well these results can be generalized to actual hand-held devices with small screens with users doing “real-world” mobile tasks. At the time of this study, an RSVP program was not available on a hand-held device, so a simulation was used on a PC. Future research will investigate RSVP under various conditions on a hand-held device. Should the results generalize as expected, RSVP may be a valuable, untapped resource for reading text on small electronic windows.

Bernard, M., Chaparro, B. S., & Russell, M.C. (2000). Is RSVP a Solution for Reading from Small Displays? [Online] http://psychology.wichita.edu/surl/ usabilitynews/ 2S/rsvp.htm. Chen, H. C., & Chan, K. T. (1990). Reading computer displayed moving text with and without self-controlling the display rate. Behavior & Information Technology, 9, 467-477. Fine, E. M., Peli, E. (1995). Scrolled and rapid serial visual presentation text are read at similar rate by the visually impaired. Journal of the Optical Society of America A, 12, 2286-2292. Forster, K. I. (1970). Visual perception of rapidly presented word sequences of varying complexity. Perception and Psychophysics, 8, 215-221. Granaas, M. M., McKay, T. D., Laham, R. D., Hurt, L. D. and Juola, J. F. (1984). Reading moving text on a CRT screen. Human Factors, 26, 97-104. Kolers, P. A., Duchnicky, R. L. and Ferguson, D. C. (1981). Eye movement measurement of readability of CRT displays. Human Factors, 23, 517-527. Juola, J. F., Ward, N. J. and McNamara, T. (1982). Visual search and reading of rapid serial presentation of letter strings, words, and text. Journal of Experimental Psychology: General 111,208-227. Juola, J. F., Tiritoglu, A., & Pleunis, J. (1995). Reading text presented on a small display. Applied Ergonomics, 26, 227-229. Legge, G. E., Pelli, D. G., Schleske, M. M. (1985). Psychophysics of Reading--I. Normal Vision. Vision Research, 25, 239-252. Muter, P., Kruk, R. S., Buttigieg, M. A., &

PROCEEDINGS of the HUMAN FACTORS AND ERGONIMICS SOCIETY 45th ANNUAL MEETING - 2001

Kang, T. J. (1988). Reader-controlled computerized presentation of text. Human Factors, 30, 473-486). Rahman, T., and Muter, P. (1999). Designing an Interface to Optimize Reading with Small Display Windows. Human Factors, 41, 106-117.

Rubin, G. S., Turano, K. (1992). Reading without saccadic eye movements. Vision Research, 32, 895-902. Sekey, A. and Tietz, J. (1982). Text displays by “saccadic scrolling” Visible Language, 16, 6276.