Validation of the Montreal Pain and Affective Face Clips (MPAFC): The role of sex and participants’ pain status

Background: The use of pain-related stimuli in experimental psychology studies has increased in the last few years. Consequently, various sets of stimuli have been created for this purpose. Aims: To analyze the validity of the pain faces of Montreal Pain and Affective Face Clips (MPAFC), in Spanish participants with and without pain. Method: A total of 291 participants completed psychological self-report and pain measures and were asked to rate the prototypicality and emotional intensity of the eight pain-related faces from the MPAFC by rating. The sample was divided into three groups depending on the participants’ pain status (chronic, acute, or pain-free). Results: Three of the eight pain faces did not reach a higher rating than 5 (on a 0-10 points scale) in both dimensions. Regarding the pain status, there were no significant differences in the ratings between groups of participants. Female faces were rated as significantly more prototypical and emotionally intense than male faces. Limitations:As we used the last image of every clip, this study is based just on static images of the pain facial expression, which may be less representative of the emotion. Conclusion: Overall, the presence of pain in participants did not significantly affect their assessment of the faces. Female faces were significantly rated as more prototypical and more emotionally intense than male faces. From our results, we conclude that experimental studies about pain should explore and report the validity of the selected stimuli to optimize the adequacy of the stimuli.