Wataru Toyoda

Influences of tactile-dot height and tip radius of curvature on the operational performance of cellular phones

Tactile dots located on operation keys of consumer products such as cellular phones contribute to improving accessibility for older people and people with visual impairment. The Japanese Standards Association (2000) and the International Organization for Standardization (2011) standardized tactile dots. However, reliable data on the appropriate sizes and the shapes was not necessarily available. The purpose of this study is to evaluate influences of the height (0.1, 0.3, 0.55, and 0.75 mm) and the tip radius of curvature (0.1, 0.3, 0.5, 0.7, and 0.9 mm) of tactile dots on the operational performance of cellular phones in younger and older people. Sighted younger and older participants, whose hand was covered by a curtain, operated cellular phones with a tactile dot on its key 5 and without a tactile dot. As the result, both participants performed better at a particular height with larger tip radius of curvature. Furthermore, older participants operated better at high dots like 0.55-0.75 mm. In contrast, younger participants performed better at 0.3 mm and relatively poorly at 0.1 mm and 0.75 mm. Thus, comparatively high tactile dots are useful for improving the accessibility of products for the older and there is an appropriate height range for the younger.

Influences of the edge radius of curvature of tactile dots and bars on their discriminability

Tactile dots and bars serve as tactile landmarks so that people with visual impairment can use same consumer products as those used by sighted people. However, reliable age-related data on the appropriate sizes and the shapes was not necessarily available. The purpose of this study is to evaluate influences of edge radius of curvature of tactile dots and bars on their discriminability in younger and older people to determine the appropriate size of tactile bars (as distinguished from tactile dots). Sighted younger and older participants tactually discriminated the tactile dots and bars presented individually, in random order, by a two-alternative forced-choice task. The results showed that both participants discriminated tactile bars from tactile dots faster and more accurately as the dimensional difference between bar length and width increased, regardless of conditions of edge radius of curvature. Therefore, longer dimensional difference between width and length of tactile bars is an important factor to discriminate tactile bars correctly. On the other hand, tactile dots with a larger edge radius of curvature have higher discriminability than tactile dots with a smaller edge radius of curvature in the case of dots of identical height.

Research on the Perceptual Size of Tactile Dots and Bars

Many countries today have rapidly aging populations, and so it becomes increasingly important that standards developers design consumer products that address the accessibility needs of older persons as well as persons with disabilities. The Japanese Standards Association is presently forming several exploratory committees to address the standardization of accessible design. In 2000, Japan enacted a standard (Japanese Industrial Standard, JIS S 0011) regulating the perceptual sizes of tactile dots and bars for use in consumer products. However, these regulations were not based on highly reliable data. Therefore, objective and quantitative data for perceptual sizes of tactile dots and bars is required for revising this JIS and for devising other standards. In this study, we examine the objectively appropriate perceptual sizes for tactile dots and bars. We determine the optimal size for the tactile dot on a cellular-phone button and the optimal relative size and shape that enable a tactile dot and bar to be distinguished from one another.