Influences of the sizes of tactile bars and dots on discriminability in people with visual impairment
Tactile bars and dots served as tactile landmarks so that people with visual impairment could use the same consumer products as those used by sighted people. However, reliable data on the appropriate sizes of products was not readiliy available. The purpose of this study was to evaluate the influence of tactile bar and dot sizes on the discriminability of the two among younger and older adults with visual impairment. This was done to determine appropriate tactile bar size (as distinguished from tactile dots). Participants tactually discriminated several sizes of tactile bars and dots presented individually, in random order, via a two- alternative forced-choice task (2AFC) using the index finger of the prefered hand. Results showed that longer dimensional differences between tactile bar width and length is an important factor for correctly discriminating tactile bars. Most participants in both groups distinguished tactile bars that were larger than +2.0 mm from tactile dots quickly and with high accuracy. Meanwhile, tactile dots with a larger edge radius of curvature had greater discriminability than tactile dots with a smaller edge radius of curvature in the case of dots with an identical diameter.