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.