The exponents (means ± s.e.m.) of the power relationships between the normal force, the limiting friction and the contact area of fingerpads at different orientations and on Perspex pads of different widths
Finger | Friction vs normal | Area vs normal | Friction vs area |
---|---|---|---|
Index flat | ↑*** 0.850±0.038 ↓** | 0.538±0.020 ↓*** | 1.554±0.094 ↑*** |
Middle flat | ↑*** 0.949±0.062 n.s. | 0.745±0.029 ↓*** | 1.269±0.076 ↑** |
Ring flat | n.s. 0.683±0.024 ↓*** | 0.853±0.041 ↓** | 0.777±0.050 ↓*** |
Little flat | ↑* 0.773±0.040 ↓*** | 0.591±0.027 ↓*** | 1.290±0.074 ↑** |
Thumb | ↑*** 0.807±0.026 ↓*** | 0.694±0.035 ↓*** | 1.121±0.083 n.s. |
Index intermediate | n.s. 0.717±0.057 ↓*** | 0.580±0.017 ↓*** | 1.219±0.113 n.s. |
Index tip | n.s. 0.561±0.048 ↓*** | 0.428±0.055 ↓*** | 1.140±0.157 n.s. |
Index on 0.75 cm | ↑** 0.808±0.033 ↓*** | 0.425±0.025 ↓*** | 1.823±0.144 ↑*** |
Index on 0.3 cm | ↑** 0.819±0.042 ↓*** | 0.205±0.024 ↓*** | 3.470±0.453 ↑*** |
The statistical tests (t-tests) show whether the exponents are significantly different from the value of 1 (right-hand side of the exponent) and 2/3 (left-hand side of the exponent): n.s., not significant; *, P<0.05; **, P<0.01; ***, P<0.001