Table 1.

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

FingerFriction vs normalArea vs normalFriction 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 flatn.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 intermediaten.s. 0.717±0.057 ↓***0.580±0.017 ↓***1.219±0.113 n.s.
Index tipn.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