Figure 2

Typical psychophysical curves from one young (A) and one older participant (B) reflecting the percentage of texture stimuli perceived rougher than the reference texture (ΔA = 750 nm) for each sound condition: Squeaking (pink), Rubbing (yellow) and Neutral (black). Symbols are the mean values obtained for 7 textures varying in roughness. JND: just noticeable difference; PSE: point of subjective equality. (C) Individual and mean JND values for the younger (dots) and older participants (triangles) in each sound condition: Squeaking (pink), Rubbing (yellow) and Neutral (black). Statistics are post hoc tests after Holm correction * (D) Individual and mean Gain indexes (%) (Squeaking in pink and Rubbing in yellow) for the younger (dots) and older (triangles) participants. The largest symbols are the mean of the groups and the horizontal bars are the median. Statistics are the main effect of the GLM (*) and t-tests different from zero ($). (E) Correlations between the two Gain indexes (Squeaking and Rubbing) within each group (Young: black dot line; Old: grey dash line). * or $ p < 0.05; **p < 0.01. Thr Threshold.