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Version: 2.0

Pain Expressivity

Similar to emotion expressivity, pain expressivity is calculated using a combination of action units as defined in the Facial Action Coding System (FACS)1. The following action units have been found to be associated with pain according to reports in the scientific literature: 4 + 6 + 7 + 9 + 10 + 12 + 20 + 26.2

Raw Variables

VariableDescription
fac_paiintsoftPain intensity ‘soft’. Continuous vector indicating intensity of pain in each video frame regardless of whether all action units for that emotion are present. Range is between 0 and 1.
fac_paiinthardPain intensity ‘hard’. Continuous vector indicating intensity of pain in each video frame, only providing non-zero value if all action units for that emotion are present. Range is between 0 and 1.

Derived Variables

VariableDescription
fac_paiintsoft_pctPercentage of frames where at least one of the pain AUs were detected.
fac_paiintsoft_meanPain expressivity ‘soft’ mean, equal to the average of all fac_paiintsoft values.
fac_paiintsoft_stdPain expressivity ‘soft’ standard deviation.
fac_paiinthard_meanPain expressivity ‘hard’ mean, equal to the average of all fac_paiinthard values.
fac_paiinthard_stdPain expressivity ‘hard’ standard deviation.

  1. https://en.wikipedia.org/wiki/Facial_Action_Coding_System
  2. Prkachin, Kenneth M. (1992). The consistency of facial expressions of pain: a comparison across modalities. Pain, 51(3), 297–306.