Tactile symbol matching of different shape patterns : Implications for shape coding of control devices

One practical use of tactual sense knowledge in the context of man-machine interface is for the design of control knobs and related devices. Shaping control devices differently is one method of coding control devices for easy tactual identification. However we still do not know how well people perceive complex shapes. The purpose of this study was to examine tactile discrimination of different geometrical shapes between males and females. Twenty-five Chinese people participated in a tactile symbol matching task. In each trial, participants were given one tactile symbol. They were asked to 'touch-read' the symbol with their thumb and index finger of dominant hand and then to match it with the target set placed in front of them as fast and as accurately as possible. The results showed that circle, square and triangle were discriminated significantly faster than other polygons and star shape patterns. Tactile symbols with less number of edges were recognized significantly faster than those with many edges. Tactile features consisting of acute edges were more easily discernible. Significant association between recognition accuracy and response time for geometric shapes was also revealed. The higher the recognition accuracy for a tactile symbol was, the shorter the response time. No significant difference between males and females was found in tactile shape discrimination. The findings of this study are useful as a reference for designers, ergonomists and other practitioners to develop better man-machine interfaces with tactual shape coding so as to improve human operator performance.