Finally, it is recorded how subjective feeling, as represented by PC1 score from Fig. 5a, is influenced by surface roughness. Fig. 7 shows variations of scores with Ra and Rp, for cut-off lengths of 2.5, 0.8 and 0.25 mm. The ‘neutral’ feeling score (PC1 = 0) coincides with Ra and Rp in the range 2–4 and 5–15m, respectively, depending on cut-off.Similar plots for dependence of PC1 score on Δq and λq lead to ‘neutral’ slopes and wavelengths from 8◦ to 17◦ and 40 to 180m, again dependent on cut-off. Feelings are not influenced by skew or kurtosis, at least for the surfaces studied here.