Comparison of front touch and back touch while using transparent double-sided touch display Tomoko Ohtani The University of Tokyo
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Tomoko Hashida The University of Tokyo
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Yasuaki Kakehi Keio University
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Takeshi Naemura The University of Tokyo
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Figure 1. User touches the back side under dual input condition.
1. Introduction When using direct-touch displays, the users’ fingers sometimes occlude the content. To avoid this problem, previous studies have proposed using the back side of a device [Hiraoka et. al., 2003] [Wigdor et al., 2007]. These approaches were shown to be useful for inputting from the backside of a device, for tasks such as selecting targets. Although these approaches have not been shown the usability of double sided touch displays, we explored how users touch both sides of a transparent display using the LimpiDual Touch (LDT) [Iwabuchi et al., 2008]. In our experiments, participants touched a target on the double-sided display. The location of the target was not predictable. We compared the reaction time (RT) and accuracy under the different input conditions (front / back / dual).
main effect for each condition, F (2, 30) = 5.89, p < 0.01. Bonferroni post hoc analysis confirmed that the dual condition was the most accurate compared to the other conditions (p < 0.05). In addition, the mean of the usage rate for touching the back of display was 0.38 (SD = 0.27) under the dual condition.
2. Experiment Sixteen peoples participated in the experiment. All participants had normal or corrected-to-normal vision and were right-handed. Testing occurred in a quiet room. They were required to touch the target as quickly and accurately as possible from the input side indicated. They used their thumbs on the front of the device, and the other fingers on the back. To allow for input with five fingers, it was grasped by the right hand (see Figure 1). The visual stimuli appeared on an LDT screen positioned on a table with a tilt of 51degrees, 32cm from the participant’s eyes. The participant fixated at the center of the screen. An input condition (front / back / dual) was presented. Under the dual condition, participants could select to touch the front or back. When the participant pushed the start button on the screen, a 5x2 grid square appeared. After a stimulus onset asynchrony of 500ms, a target stimulus (180x 180mm) appeared for 500ms. After the participant touched the target, feedback comments indicated whether he/she had selected the correct target. This experiment was to measure RT and accuracy. Following 30 practice trials, the participants took part in 600 experimental trials. The trials’ presentation was balanced such that the target appeared an equal number of times for each condition. Trials’ conditions were randomly mixed.
3. Results Figure 2 depicts the mean RT and accuracy for each condition. An ANOVA on the mean RT revealed a significant main effect of input-condition, F (2, 30) = 24.83, p < 0.01. Bonferroni post hoc analysis confirmed that RT for the front condition were faster than those for the back condition (p < 0.01) and the dual condition (p < 0.01). RT for the dual condition was faster than those for the back condition (p < 0.05). For the accuracy rate, there was a significant
Copyright is held by the author / owner(s). SIGGRAPH 2011, Vancouver, British Columbia, Canada, August 7 – 11, 2011. ISBN 978-1-4503-0921-9/11/0008
Figure 2. Mean reaction times and accuracy for each input condition. These results clearly suggested that when users touch both sides, this is the most accurate way though it is slower than from the front. The reason is that the user could see the location and motion of his/her finger on the back of the screen. In other words, even if users are accustomed to using the front, they tend to use a combination of both sides.
References HIRAOKA, S., MIYAMOTO, K., AND TOMIMATSU.I. 2003. BEHIND TOUCH, A TEXT INPUT METHOD FOR MOBILE PHONE BY THE BACK AND TACTILE SENSE INTERFACE, INFORMATION PROCESSING SOCIETY OF JAPAN, INTERACTION’03, 131-138. WIGDOR, D., FORLINES,C., BAUDISCH,P., BARNWELL,J., AND SHEN,C. 2007. LUCIDTOUCH: A SEE-THROUGH MOBILE DEVICE. IN PROC.UIST’07, ACM, 269-278. IWABUCHI,M., KAKEHI,Y., AND NAEMURA,T. 2008. LIMPIDUAL TOUCH: INTERACTIVE LIMPID DISPLAY WITH DUAL-SIDED TOUCH SENSING. IN SIGGRAPH’08, ACM, POSTERS.
