Discussion
Previous studies of the perceived intensity of tactile stimuli have
relied on overt motor or verbal responses. However, a more objective
measure of perceived tactile intensity has so far been lacking. Such an
index is useful when overt responses are not possible or to avoid
explicit bias. Furthermore, it is crucial to tear apart the objective
components of touch processing from subjective reports. Here, we set out
to systematically test pupil size change as an objective measure of
perceived intensity of tactile stimulation. We found greater pupil
dilation following stimulation of constant intensity on more sensitive
parts of the body (Experiment 1) and following higher stimulation
intensity on the finger (Experiment 2). This highlights the usefulness
of pupillometry as a means of studying tactile perception.