The phenomena of tactile concentric-figure on tactile recognition by index finger

Transcription

1 The phenomena of tactile concentric-figure on tactile recognition by index finger Ying-Chu Duan a, and Yung-Hsiang Tu a* a Department of Industrial Design, Tatung University, No. 40, Sec. 3, Zhongshan N. Rd., Taipei, Taiwan *Corresponding Author: tys@ttu.edu.tw ABSTRACT On the design of tactile map, building, landmarks, or other unit of objects needed to be differed to each other. Some conditions, concentric-figures are unavoidable. These concentric-figures can be strongly sensed but also confused when they are line up together. This work intended to see the different effects on tactile recognition among different Squares. Sixty participants including 30 visually impaired persons and 30 blind-folded sighted subjects were asked to recognize the size of tactile square symbols which differed at shape Size (original size, 120% size, 140% size, and 160% size), Gap space (20%, 40%, and 60%), and all of the combinations showed twice. Participant was asked to response whether the size of inner figure was original size. Researcher measured the misjudge rate. Result shows the significant highest misinterpret rate happens at the condition of 120% size, no matter at what Gap level. It should be concluded that the space between frame figure and inner figure, concentric-figures, should be designed larger than 120% of inner size in order to avoid the possible misinterpret of the size of tactile symbol. Keywords: tangible graphics, concentric-figure, tactile misinterpret, tactile map, visually impaired people 1. INTRODUCTION In a normal city map, there are lots of buildings intersected with different kinds of traffic roads, railways, and MRTs. In a general condition, even sighted people like researchers, we have to recheck the map several times in order to make sure the location of the goal and plan a proper way to the goal. Owing to the complicated arrangement of elements in a map, we might frequently face some confused situation that hardly can tell the right way. This partially cause by the complicated intersection of all differed elements (figures and graphics) in the map. In the same situation for blind or visually impaired users, visual maps are transformed into tactile maps. Those users are familiar at tacit contact rather than visual information input. How to raise the performance of recognition of figures at tactile map is the major issue for designers. Many papers reported the state of art of this map design, see [1, 2, 3, and 4]. There were some contracted points among those papers, such as symbol design guidelines, presentations of the map and location of putting it. The major and early research on the issue of design guidelines should be mentioned is Edman [5], who offered the experience and practical opinions about making from a single tactile symbol to many tactile books. Some researchers argued that design guidelines are necessary for users to produce it independently, [6]. Most countries has announced their own standards for the design of tactile map [7, 8]. On the practice field for self-made user, American Printing House [9], is one of the most confident origination that continually promote their practical results for end users.

2 In recently years, tactile map are likely to use in the traffic stations, university, and other public area, which emphasis the importance of tactile map [10, 11, 12]. As the variety of elements, shapes, and complex intersections on the tactile map. This leads an immerging need to study the guidelines for more precisely definition on such complexity conditions. This study is one of our serial work on the issue for knowing a better design for complex condition on variety needs of tactile maps, see [13, 14, and 15]. The aim of this work is to know the effects of concentric- figure on tactile recognition. 2. METHOD There was a serial of simple shape designed for this test, Square. In our other studies [x, xx], the similar tactile symbols were 10mm. We realized that the size for our human finger to percept a figure and tell the image in one single touch is about 8-10mm, so the standard size of tactile symbol was 10mm in this test. In this case of concentric symbols, the assumed factors are Size and Gap, see figure 1. Researchers defined the names in the figure for making concentric symbols. The inside symbol called inner figure, the outside symbol called frame figure. And we decided the factor and levels, firstly, the Size factor which has four levels, 100%, 120%, 140%, and 160% related to standard size (10mm), of its side-length. This simulated the situation of diverse size of buildings in an actual tactile map. So the size of inner figures were 10mm, 12mm, 14mm, and 16mm. Then secondly, the Gap factor, defined the space between inner figure and its frame figure, had three levels: 20%, 40%, and 60% of its side-length for a square. In the material, each combination of levels in Size and Gap factor showed twice, that made 24 symbols in a sheet (4 inner x 3 frame x 2 times), see table 1. To avoid the risk of order effect, we prepared three different arrangements for experimenter to choose one randomly before the test. Figure 1. The material sheet with tactile squares in this study Table 1 the factors (Size/Gap) and levels in this study Factor Tactile Symbol Size Gap Level Square 120% 20% 140% 40% 160% 60%

3 Sixty participants with mean age of 31.0 years were randomly assigned to the test, including 31 females and 29 males. Thirty of them were visually impaired persons (VIPs), including 16 blinds and 14 low visions. Other 30 participants were sighted students recruited from Tatung University. All participants were self-reported with no injured at dominant hand and also index finger. The participant set comfortably on an adjustable chair and faced to a desk. The experimenter showed the example sheet to him and explained the procedure of the actual test. Participant moved his non-dominate index finger to feel size of the standard symbol located on the middle bottom, and also moved his dominate index finger to touch the first symbol, on the top left side of the test sheet. Experimenter told the participant that he was required to response the answer yes or no to the experimenter for 2 minute on each symbol. It meant he had to tell whether the size of touched symbol was the standard symbol for yes, or not the same for no. The experimenter recorded the participant s answer. After the test, a gift was given to the participant for the participation. 3. RESULTS Researchers interested in the misinterpret rate for all level combinations. Those errors tell us what the bad designs are and it might lead some guidance for avoiding them. So the responses of participants were reformed into error rate in percentage. A repeat-measurement of ANOVA shows that at least one level among Gap and Size factor has the different error rate than others, F(4, 56)=16.87, p< Post Hoc with LSD method shows that the largest misinterpret rate is the 120%size (44.4%), and the least misinterpret rate happened at 160%size (16.9%). Other level combinations had the middle values between 44.4% and 16.9%, as a group. This evidence shows that Size factor affects larger than Gap factor on the concentric shape identification problem, see figure 2. Misinterpret Rate 60% 50% 40% 30% 20% 10% 0% 44.4% 30.2% 34.1% 32.7% 24.7% 16.9% 120% Size 140% Size 160% Size 20% Gap 40% Gap 60% Gap Square Figure 2. The misinterpret rate of the Size factor and Gap factor The Size factor has a significant impact to our fingertip as shown. If the distance of two similar tactile figures less than 20% of the standard size, says 10mm, then our finger can hardly figure out the difference between them. This hints us that some design changes need to be made for lower the possible misunderstanding of the meaning of tactile shape. Such design change is not a real different but it is only a way of raising the dissimilarity for identification. When two shapes have a size differed than 60%, our finger is capable in judging the

4 variance. So it is a good rule for designer that keeping two similar tactile shapes away from each other in 60% of size. And researchers would recommend that one way to avoid the situation of misjudging concentric shapes is to magnify the differences of two tactile shapes. This phenomena also shows a hint to other field for VIPS. Recently, Rosenblum and Herzberg, [16], asked 12 VIP children about the use of mathematics tactile rulers. Most youths indicated they preferred graphics that had clear distinctions between elements. Most of children of Visual impaired are unfamiliar to the ruler from APH. When they are hint to use the ruler with inches or centimeters, some of them did not actually use the ruler to confirm their measurement at classes. And the response of distance from them tends to be longer than actual distance. It is such match that to ask our finger to tell from two nearly tactile symbols is a task with much difficulty, not only to children but also to adult. And we should not design such a tactile map to challenge the nature of the finger. REFERENCES [1] Rowell, J., & Ungar, S. The world of touch: an international survey of tactile map. Part 2: design, British Journal of Visual Impairment, 21, pp , [2] Koch, W.G. State of the art of tactile maps for visually impaired people, in True-3D in Cartography (pp ). Springer, Berlin, [3] Tatham, A. F. Tactile mapping: Yesterday, today and tomorrow, The Cartographic Journal, 40(3), pp , [4] Brock, A.M., Truillet, P., Oriola, B., Picard, D., & Jouffrais, C. Interactivity improves usability of geographic maps for visually impaired people, Human Computer Interaction, 30(2), pp , [5] Edman, P.K. Tactile Graphics, New York: American Foundation for the Blind, [6] Tatham, A.F. Achievable goal or Chimera? Standardization in tactile mapping, In proceeding of the 20 th International Cartographic Association Conference, 2923, Beijing, August, [7] Gardiner, A., Perkin, C. Best practice guidelines for the design, production and presentation of vacuum formed tactile maps, [8] Braille Authority of North American (BANA). Guidelines and standards for tactile graphics, 2010, Available: [9] American Printing House for the Blind (AHP). Guide to designing tactile illustrations for children s book, Louisville, KY, [10] Perkins, C. Cartography: progress in tactile mapping, Progress in Human Geography, 26(4), pp , [11] Luxton, K., Banai, M., Kuperman, R. The usefulness of tactual maps of the New York City subway system, Journal of Visual Impairment & Blindness, 88(1), Jan-Feb 1994, pp [12] Papadopoulos, K., Charitakis, K., Koustriava, E., Kartasidou, L., Stylianidis, E., Kouroupetroglou, G., & Yilmaz, E. Specification of Symbols used in Audio-tactile maps for individuals with Blindness, in International Conference on Computers Helping People with Special Needs (pp ). Springer International Publishing, [13] Tu, Y.H., Wu, C.F., Chung, T.J. and Chen, I.Y. The effects of localized space on tactile perception of index finger, in Asia-Pacific Industrial Engineering and Management System Conference (APIEMS 2007), 824, Dec., 2007, Kaoshiung, Taiwan. [14] Tu, Y.H., Chen, L.C., Hung, T.T., Liao, P.C. and Wang, Y.L. The effects of length and type on the recognition of tactile symbol, in Proceeding of IIE Asian Conference (IIE 2011), June, 2011, Shanghai, China. [15] Tu, Y.H., Ko, T.M., Huang, W.N., Jheng, S.Y., Wang, Y.L., Liao, P.C. and Hung, T.T. The effects of size and shape on the tactile symbol recognition, in Proceeding of Asian Conference on Psychology & Behavioral Science (ACP 2012), March, 2012, Osaka, Japan. [16] Rosenblum, L.P., Herzberg, T.S. Braille and Tactile Graphics: Youth with Visual Impairments Share Their Experiences, Journal of Impairment & Blindness, May-June, pp , ACKNOWLEDGMENTS The partial grand support is from Ministry of Science and Technology at the project of MOST E and NSC C-036-E. The authors would like to express our appreciations for the fully help from Institute for the Blind of Taiwan, Mu-Kuang Rehabilitation Center for the Blind, Taipei School for the Visually Impaired, and Taiwan Foundation for the Blind. And the completely

5 cooperation of all of the recruited participants from different originations are more than grateful. The special thanks are delivered to the excellent team work of those master students, including Wan-Ning Hauang, Siang-Yao Jheng, Tzu-Mei Ko, Tsao-Ting Hung, Yu-Jou Chiang, Chiao-Chuan Kuo, Ka- Ching Lee, and Jhe-Hua Yi.