A study of the role of surface parameters on the relationship between biotribology and cognitive perception involved in the design of tactile graphics

Tactual encoding of information is an essential aspect of communication in many aspects of life, but especially so for persons with visual impairments. The most common encoding is the use of topological features on a static medium such as paper. While Braille is widely used and effective for text transcription, the effective use of tactile graphics to communicate spatial or graphical information is less standardized. Tactile graphical techniques typically employ collections of individual topological features or texture patterns to communicate spatial in-formation (maps, plots, diagrams), with the goal of minimizing reader confusion among the elements. In this study, the authors investigated the tribology and perception aspects of this complex issue in order to identify fundamental surface parameters which play a dominant role. Using texture specification guidelines published by the Braille Authority of North America (BANA), the investigators produced raised parallel-ridge textures on thermally activated tactile paper. The texture parameters modified included the width of ridges, spacing between ridges, and the inclination of the ridges to the pattern boundaries. Subjects reported their perception of tactile similarity or difference between members of texture pairs that were presented under a blind. Measurements of friction force were also collected for these textures to determine if friction mechanisms were most responsible for perceptive ability, or if other surface attributes played a dominant role. The study found that modifying pattern pitch improved perceptive ability to differentiate between adjacent mismatched texture patterns, but that ridge width had a deleterious effect. The results suggested that perceptive ability was not strongly related to various friction mechanisms proposed, but was closely correlated with changes in the number of pattern ridges in contact with the fingertip during tactile graphic exploration.