Perceptual weighting of pain behaviours of others, not information integration, varies with expertise

Background Being able to estimate effort pain in patients is important for health care providers working in physical rehabilitation services. Previous studies have shown that clinicians and physiotherapists underestimate patients' pain. Methods The present study examined how two sources of visual information, namely body kinematics (movement speed and postural constraints) and facial expressions are integrated in order to estimate effort pain magnitude experienced by a paraplegic person performing a sitting pivot transfer. In addition, the effect of familiarity with paraplegia on judgment was assessed by comparing performance among physiotherapists, paraplegic patients and unfamiliar participants. Functional measurement was used to determine the psychophysical law of visual information integration carried by pain behaviours (guarding and facial expression). Results Results indicate that guarding behaviour (specified by movement speed) carried important information for perceived effort pain independently of familiarity. In contrast, facial expression of pain was relevant only to unfamiliar and physiotherapist participants and not to paraplegic participants. Even if physiotherapists underestimated effort pain as compared to the other groups, they relied more strongly on facial expression, than other participants, in their estimation of effort pain expressed by a paraplegic patient. Conclusions These results bring further insights into understanding physiotherapists' perception of patients' pain. In order to improve their ability to adapt the difficulty of the rehabilitation sessions, they should learn to raise their global level of pain magnitude estimation (for example, by performing themselves the body movement) instead of overweighting facial pain expression signals.