Extended Data Fig. 7: Perceptual intensity of vibration and torsion.

a,b, Vibration current amplitudes of perception thresholds (n = 12, six males, six females, ages 20–36 years). a, Compressed-state vibration. b, Relaxed-state vibration. c, Relative perception of vibration in the transducer with respect to a commercial LRA (dotted line, equivalent perception; n = 12, six males, six females, ages 20–36 years). d–g, Perceptual intensity evaluated according to its definition in Methods for n = 14 human participants (eight males, six females, ages 23–31 years) under four ring–disc configurations. The left column shows mean values reported by each subject (n = 5 repeat measurements; bars, standard deviation) and the right column reflects all subjects (n = 14; bars, 1.5 interquartile range; shaded box, range between 25th and 75th percentiles; horizontal line, median; ×, mean; ◆, outliers from 1.5 interquartile range). According to the Friedman test, a statistically significant difference can be seen within each ring–disc configuration (P < 0.0001) and each showed a moderate positive correlation between ratings and rotation angles (Spearman correlation, ρ ≥ 0.58), which was highly statistically significant (P < 0.0001). d, Outcomes reported for rotation and indentation of the ring, in which the ring was rotated to angles of 0.33°, 0.66° and 1° with a static indentation of 0.2 mm. e, Outcomes reported for rotation of the disc, in which the disc was rotated to angles of 5°, 10° and 15° with a static indentation of 0 mm. f, Outcomes reported for rotation and indentation of the disc, in which the disc was rotated to angles of 5°, 10° and 15° with a static indentation of −0.4 mm. g, Outcomes reported for rotation and indentation of the ring and disc, in which the ring and disc were rotated to angles of (0.33°, 5°), (0.66°, 10°) and (1°, 15°) with a static indentation of (0.2 mm, −0.4 mm). h–j, Torsion and indentation array discrimination experiments. h, Illustration and photograph of the apparatus setup, which includes three torsion actuators (A, D and E) and two indentation actuators (B and C). i, Discrimination between indentation and torsion, combined results for 15 healthy participants (seven males, eight females, ages 23–31 years). Accuracy was averaged over 15 subjects with ten repeated trials (n = 150). j, Discrimination between patterns of torsion, combined results for 12 healthy participants (seven males, five females, ages 23–31 years).