Comparing reading processes on e-ink displays and print

An e-book, or “electronic book,” is a digital format of a book. Electronic books open new possibilities in the field of reading. More functions than just displaying text can be integrated. For reading an e-book on a personal computer (PC), mobile phone, or personal digital assistant (PDA), a specialized software application for e-reading is necessary (e.g., Stanza). These reading devices have the disadvantage that the interface usually is an LCD display, which provides a relatively low contrast, especially in daylight conditions. Previous research showed that CRT and LCD displays are associated with impaired reading performance [1], [2], [3]. For instance, Mayes et al. [4] showed in their study that participants needed more time to read a text on a LCD screen than on a print. Cushman [5] reported that visual fatigue is significantly higher when reading black objects on a white screen than when reading on paper. Consequently, reading from LCD tends to be slower than reading from paper. Gould et al. [6] attempted to specify the causes of slowed reading on screens by analyzing eye movements. Results revealed that when reading from screens, participants made significantly more fixations per line, which, as a consequence, reduced reading speed. On average, they made 15% more forward fixations, while other eye movement parameters (like regressive saccades or re-fixations) for screen reading were comparable to those of reading on print. The authors explained the higher number of fixations in terms of image quality variables. Recent studies [7] suggest that such differences between print and screen have decreased but emphasize that reading behavior also depends on moderating variables like computer experience or the task to be performed. Nevertheless, there is still evidence of a preference for reading from print compared to doing so on LCD screens [8].

In addition to e-reading software for general electronic devices, there exist dedicated e-reading devices. These devices are commonly called e-book readers (or e-readers) and are purpose-built for reading. The first e-reading devices were prototyped in the late 1960s by Alan Kay, and they were later embodied in several product generations (Apple Newton, Palm Pilot) [9]. These series had built-in active LCD displays. Around the year 2000, several companies (e.g., Franklin, Hanlin, Hiebook, Rocket eBook) released new specialized e-reading devices. The latest generation of e-readers includes the Sony Reader, the Amazon Kindle, and the iRex iLiad. This generation of e-readers contains a different display technology: the active LCD displays have been replaced with “e-ink” technology [10]. The basic elements of e-ink are tiny microcapsules, with a diameter comparable to that of a human hair. Each microcapsule contains positively charged white particles and negatively charged black particles suspended in a clear fluid. When an electric field is applied, the white particles move to the top of the microcapsule where they become visible to the user. This makes the surface appear white at that spot. At the same time, the black particles move to the bottom of the microcapsules, where they are not visible. By reversing the electric field, the black particles appear at the top of the capsule, which now makes the surface appear dark at that spot [11]. Since only refreshing the display but not maintaining it requires energy, e-ink technology has the advantage of low power consumption, thereby allowing for increased battery life or reduced weight [9].

However, there are many other factors that set the reading experience on e-readers apart from that on printed-paper books or on screens. The size of the device, the scalable font size, and the new e-ink technology make it different from reading from printed paper or from screen. It seems that the advancements in screen quality with the e-ink technology have made reading from these devices increasingly acceptable. Additionally, the advantages in terms of low weight, small dimensions, and freedom of mobility are evident. Previous studies have shown that reading on an e-reader without e-ink display causes significantly higher visual fatigue than reading on print [12]. An assessment of the readability of e-readers with e-ink displays showed no difference in reading speed between the Kindle2 and a printed book [13]. This result suggests that e-ink technology allows for a reading process that is similar to that of reading print. However, there is no empirical evidence that the new e-ink technology is beneficial with regard to the reading process.

The objective of the present study is to evaluate and compare human reading behavior on e-ink and print as measured by eye tracking. If reading on e-ink displays is similar to reading print, then no differences in eye movement patterns (e.g., progressive- and regressive saccades and fixations) and in reading performance (e.g., reading speed) should be found.