HAPTIC CURVATURE DISCRIMINATION AT SEVERAL REGIONS OF THE HAND

Static haptic discrimination of the curvature of convex, concave, or s traight 20-cm-long strips was investigated for nine placements on the hand. In one condition, the strips were touched with the palmar side o f the hand, and in the other condition, with the dorsal side. The infl uence of the lengths of the strips, and thus of contact lengths, was a lso investigated. For all placements, discrimination was poorer in the dorsal than in the palmar condition, owing to poorer cutaneous resolu tion on the dorsal side of the hand (the kinesthetic stimulation was t he same in both conditions). Thus cutaneous stimulation is important. In both experiments, performance appeared to depend primarily on conta ct length. Moreover, the discrimination thresholds for all different p lacements and contact lengths followed the same trend. We conclude tha t in these experiments the effective stimulus for the discrimination o f curved strips is the total difference of local surface attitude-that is, the slope difference over the far ends of the stimulus.