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William Grussenmeyer, Leo Quijano, Fang Jiang; Tactile Perception of Spatial Distances in Blind Humans. Journal of Vision 2016;16(4):28. doi: https://doi.org/10.1167/16.4.24.
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Blind individuals show superior abilities in auditory spatial processing (see Collignon et al. 2009 for a review). Similarly blind braille readers show heightened tactile spatial acuity (e.g., Von Boven et al., 2000; Wong et al., 2011). Here we examined whether blind individuals show enhanced ability to integrate tactile vibration in order to estimate the relative displacement between the finger and surface.
Subjects were asked to compare two haptified lines and determine which of the two lines are longer. The haptification is dependent on the length of the line: the vibrations pulsate faster as the subject's finger moves closer to the end of the line. We tested three line orientation conditions: vertical, horizontal, and diagonal. The experiment was implemented on an Android tablet, which vibrated for the vertical orientation, and an Android Smartwatch, which vibrated for the horizontal orientation. Note that for diagonal orientation, both tablet and smartwatch vibrated. All lines originated from the lower left corner of the tablet. Subjects wore Smartwatch on their non-dominant hand and sighted subjects were blindfolded.
Thresholds were measured using a staircase procedure (3 down 1 up; 50 trials per condition) and calculated by fitting the data with Weibull psychometric function. We found similar thresholds across three orientation conditions. Despite huge inter-individual variability within both blind and sighted groups, we observed a trend towards lower threshold in blind subjects. Our preliminary results suggest that blind individuals might be better at forming a representation of spatial distance from tactile vibration cues.
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