Communication of pain intensity and unpleasantness through magnitude ratings: Influence of scale type, but not sex of the participant

A critical aspect for much human pain research is the ability of participants to communicate their first person, experiential perspective to a third person observer. This communication is frequently accomplished via pain ratings. The type of scale and how participants/patients may differentially use the scale has a major influence on the communication of pain experiences. The present study examined the role of sex on the pain rating process using both noxious and innocuous stimuli and two different types of rating scales. Participants underwent noxious heat, auditory and visual stimulation paradigms. Pain intensity and unpleasantness ratings were collected using the visual analog scale (VAS) and numerical rating scale (NRS) in a random order. For noxious heat stimuli, low (44-45{degrees}C) and high (47-48{degrees}C) intensity stimuli were delivered. To identify if one rating scale allows better discrimination between different stimulus intensities and if this is dependent on sex, discrimination thresholds were calculated. Significant effect for rating scale and intensity level of stimuli were found for all stimulus modalities (noxious heat, auditory and visual) indicating that higher intensity and unpleasantness ratings were found using the NRS compared to the VAS. No effect of sex or interaction with sex was found. No differences in rating scale and sex were found for the discrimination thresholds. Biases in rating scales usage exist with NRS yielding higher ratings to the same stimuli. However, this bias does not appear to contribute significantly to sex differences in pain.