Vibration thresholds in a dynamic tactile display.(MOTOR BEHAVIOR)(Author abstract)(Report)

Previous research has shown that exposure to short-term hand and arm vibration degrades several aspects of motor performance (Fischman & Lehman, 2004; Gerard & Martin, 1999; Martin et al., 1991). However, vibration may be useful for helping blind individuals use the internet. We are developing a prototype board that maps low levels of vibration to locations on a computer monitor. The initial goal of the current project was to determine the just noticeable difference in levels of finger vibration that can be correctly detected by an individual. Thirty-three sighted participants placed their preferred index finger on an accelerometer mounted on a vibratory shaker that vibrated at frequencies from 50 to 130 Hz in 20-Hz increments. All possible pairwise combinations were presented, and participants made a "same" or "different" discrimination to each pair. On 25 trials participants were able to hear the sound of the shaker ("Sound"), and 25 trials were performed with headphones ("No-Sound"). Overall, the percentage of incorrect discriminations was 15.4% for "Sound" and 16.4% for "No-Sound." This difference was not statistically significant, p > .05, indicating that hearing the vibration provided no advantage. Only four pairings produced 100% correct discriminations, and these differed by at least 60-Hz. The most difficult discrimination (74% error rate) was the pairing of 90-Hz followed by 70-Hz. However, when 70-Hz preceded 90-Hz, the error rate was only 32%. Sighted humans can accurately discriminate levels of finger vibration in the range tested when the pairings differ by at least 40-Hz.

Mark G. Fischman (F) and Michael A. Urbin, Auburn University

(fischmg@auburn.edu)

An (F) denotes Fellow status in the AAHPERD Research Consortium as of November 2010.