Detecting Feigned Pain Using an Eye-Tracker Integrated Numerical Pain Rating Scale (NPRS)

The Numerical Pain Rating Scale (NPRS) is routinely used to assess pain severity. A recently developed NPRS integrated the pain scale with an eye tracker (NPRS_ETI). As part of this study, we explored the NPRS_ETI's utility to detect feigned pain, an ongoing challenge facing clinicians. To achieve this aim, chronic pain outpatients were randomly assigned to a simulation (i.e., requested to exaggerate their pain; n = 34) or a control condition (i.e., requested to genuinely report their pain severity; n = 35). They then rated their pain using the NPRS_ETI. Eye movement analyses indicated that simulators spent more time gazing at the higher NPRS_ETI pain ratings before providing their pain ratings and less time at the leftward (“No pain”) anchor afterward. The discrimination capacities of these measures, however, were poor. In contrast, pain ratings using the NPRS_ETI showed excellent discriminative capacity, with a pain rating of 10 associated with 94.3% specificity and 26.5% sensitivity. Overall, the study's findings further indicate the feasibility of incorporating an eye tracker to evaluate the severity of pain. Though the findings at present do not support the utility of NPRS_ETI-based eye movement measures as validity indicators, pain ratings showed promise as a simple screen of feigned pain. The preliminary nature of the findings, however, calls for further research. Such research may aid in further developing effective indicators of feigned pain and hopefully clarify cognitive processes (e.g., experienced cognitive load) involved in pain deception. Perspective: The NPRS_ETI enables pain ratings by patients with severe motor and speech impairments. While eye movements were not adequate in detecting feigned pain, participants' pain ratings showed initial promise. As this is a preliminary study, further research is recommended.