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Pupil dilation reveals the intensity of touch
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  • Antonia Francisca Ten Brink,
  • Iris Heiner,
  • Chris Dijkerman ,
  • Christoph Strauch
Antonia Francisca Ten Brink
Utrecht University

Corresponding Author:[email protected]

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Iris Heiner
Utrecht University
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Chris Dijkerman
Utrecht University
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Christoph Strauch
Utrecht University
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Touch is important for many aspects of our daily activities. One of the most important tactile characteristics is its perceived intensity. However, quantifying the intensity of perceived tactile stimulation beyond subjective self-reports remains challenging. Here, we show that pupil responses can objectively index the intensity of tactile stimulation in the absence of overt participant responses. In Experiment 1 (n=32), we stimulated three reportedly differentially sensitive body locations (finger, forearm, calf) with a single tap of a tactor while tracking pupil responses. Tactile stimulation resulted in greater pupil dilation than a baseline without stimulation. Furthermore, pupils dilated more for the more sensitive location (finger) than for the less sensitive locations (forearm, calf). In Experiment 2 (n=20) we extended these findings by manipulating the intensity of the stimulation with three different intensities, here a short vibration, always at the little finger. Again, pupils dilated more when being stimulated at higher intensities as compared to lower intensities. In summary, pupils dilated more for more sensitive parts of the body at constant stimulation intensity and for more intense stimulation at constant location. Taken together, the results show that the intensity of perceived tactile stimulation can be objectively measured with pupil responses – and that such responses are a versatile marker for touch research. Our findings may pave the way for previously impossible objective tests of tactile sensitivity, for example in minimally conscious state patients.
Submitted to Psychophysiology
23 Jan 2024Editorial Decision: Revise Minor
24 Jan 20242nd Revision Received
24 Jan 2024Submission Checks Completed
24 Jan 2024Assigned to Editor
24 Jan 2024Review(s) Completed, Editorial Evaluation Pending
26 Jan 2024Editorial Decision: Accept
16 Feb 2024Published in Psychophysiology. https://doi.org/10.1111/psyp.14538