Figure 1

Tactile discrimination ability for the two groups. (a) Proportion of correct answers in identifying whether the stimulus was different to the reference sample Ref100 (100 µm in wrinkle wavelength). The difficulty of the task clearly increases for both groups as the wavelength of the stimulus texture approaches that of the reference. The “break point” (defined as when the success rate falls below 80%) is seen for S20 (20 µm) for the elderly group and for S60 (60 µm) for the young group (N = 30 for both groups). (b) Box plot of the means from each participant in the two groups (N = 2 × 30), showing the tactile discrimination ability of S20 versus Ref100 as well as the correct responses for Ref100 versus itself (meaning “same” as the correct answer). Since the young and the elderly groups have a very similar proportion of correct responses for the latter task, the tendency to guess “different” is the same for both groups when the task is perceived as difficult.