Trial timeline of the experiment.

Participants are seated with the electrodes of both the electrical stimulation and the ECG attached. Each trial starts with a fixation cross (60 seconds), after which the noxious stimulation is administered and the pain intensity (i.e., Numerical Rating Scale) and unpleasantness (i.e., Likert scale) ratings are collected. After each trial, a pause screen of 45 seconds was shown (i.e., ISI, interstimulus interval), after which participants proceeded to the next trial by pressing the spacebar. The trial timeline was identical for both the no-feedback and feedback phases, with the only exception that in the feedback phase participants were provided with the acoustic feedback (i.e., slower, faster, congruent) about their HR, reproduced for the whole fixation period (60 seconds) preceding the shock.

a Intensity pain ratings (Numeric Pain Scale) b Unpleasantness ratings (5-points Likert Scale) c Real cardiac frequency. Values consist of the central tendency of change of pain intensity (a), unpleasantness (b) and heart rate (c) associated with the exposure to the faster vs. slower cardiac feedback, relative to the congruent feedback. Values of zero on the vertical axis would represent no change relative to the exposure to the veridical congruent feedback. Positive and negative values would represent an increase and a decrease, respectively. The plot consists of a violin plot, a boxplot, and datapoints. In the boxplot, the line dividing the box represents the median of the data, the ends represent the upper/lower quartiles, the extreme lines represent the highest and lowest values. The code for plot visualization has been adapted from van Langen, 2020.

a Intensity pain ratings (Numeric Pain Scale) b Unpleasantness ratings (5-points Likert Scale) c Real cardiac frequency. Values consist of central tendency of the change of pain intensity (a), unpleasantness (b) and heart rate (c) associated with the exposure to the faster vs. slower exteroceptive feedback, relative to the congruent feedback. Values of zero on the vertical axis would represent no change relative to the exposure to the veridical congruent feedback. Positive and negative values would represent an increase and a decrease, respectively. The plot consists of a violin plot, a boxplot, and datapoints. In the boxplot, the line dividing the box represents the median of the data, the ends represent the upper/lower quartiles, and the extreme lines represent the highest and lowest values. The code for plot visualization has been adapted from van Langen, 2020.