Pupillometric assessment
Adhesive tape was used to attach the tactor to the tip of the right little finger, which was hidden from view. A foam ring was placed at the base of the little finger to prevent it from touching the adjacent ring finger.
The experiment consisted of 50 trials per stimulus intensity (i.e., none, low, medium, high), resulting in 200 trials in total. Stimulus intensities were randomised within clusters of 20 trials, to ensure a balanced presentation. The trial sequence was similar to that in Experiment 1, except that the tactile stimulation lasted for 80 ms and the pupil response was recorded for 1.58 s after stimulus onset.