Study Provides Insights Into People’s Certainty Levels When Rating Their Pain

When asked to rate their pain on a 0 to 10 scale, people reacted faster when they were more confident of their rating, according to a new study published in Scientific Reports. The study, which was funded by the National Center for Complementary and Integrative Health and led by researchers from the National Institutes of Health and the Karolinska Institute in Sweden, also showed that people experience variations in their confidence when rating pain. The findings shed light on factors that guide judgments about pain and suggest that metacognition plays a role.

Clinicians and researchers rely on self-report methods, like a visual analogue scale or verbal pain report, to understand how much pain a patient is feeling and select the right treatment. Understanding how people make decisions when rating pain is therefore important. A critical part of understanding the process is determining whether people are capable of pain metacognition—awareness of their own confidence in their pain—and whether specific measures can predict people’s certainty or uncertainty about their pain ratings.

Eighty healthy people underwent 24 trials of varying acute thermal pain on their forearms. After each trial, participants looked at a 0 to 10 visual analogue scale for 3 seconds and then rated their pain. Zero meant no sensation and 10 meant the most pain imaginable. Researchers recorded the number of eye fixations participants made while viewing the pain scale and the time participants took to record their pain ratings. Immediately after each pain rating, participants rated the uncertainty in their rating using a 0 to 100 visual analogue scale in which 0 meant complete certainty and 100 meant complete uncertainty.

The study’s findings suggest that people are not always confident about the pain they report and that they are aware of this fact. Pain rating reaction times decreased as confidence increased, meaning participants were faster to rate their pain when they were more confident. Confidence in pain ratings increased over time as participants gained more experience with the pain trials and made more metacognitive judgments about their pain. This effect of experience supports the idea of future pain studies including practice trials or calibration procedures to increase the likelihood that participants will have confident pain reports.

Participants’ confidence was less clearly associated with the number of eye fixations when they viewed the pain scale. Participants who had very strong relationships between heat temperature and pain displayed more eye fixations when they were less certain, but these effects were not observed for all participants, and did not predict trial-by-trial confidence ratings. This suggests that reaction time, which is an easier measure to collect, is a more reliable marker of confidence in pain ratings.

The authors recommend that future research incorporate confidence ratings to further understand features that drive confidence and uncertainty in pain and to measure whether pain metacognition interacts with other forms of pain modulation. For example, patients who are uncertain about their pain relief might be less likely to adhere to treatment than patients who are confident, and might benefit from more in-depth consultation. Understanding these additional features will improve the ability to tailor pain treatment and address all aspects of patients’ pain, including confidence in their pain decision making.