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Last updated: Fri, Jun 30, 2017
Can a person tell how much another person hurts by looking at them? The answer is a qualified, "Yes." Facial expression is nonlinguistic communication and it is believed to be at least in part genetically based1 or instinctive. Facial expression is usually available as a means of communication, and facial expressions are closely attended to by others.
The Facial Action Coding System (FACS) is an organized system for describing and analyzing facial expressions. It is based on defined positions or motions of the many facial muscles. FACS is usually applied by recording facial expressions and later analyzing them in slow or stop motion. Numerous studies have analyzed the face during acute pain, "persistent pain," and evoked pain. The studies found a pattern. The face in pain has a lowered brow, tightened orbits (the area surrounding the eye socket), raising of the upper lip and wrinkling of the nose, and narrowing of the eyes. The mouth may be stretched horizontally, the corners of the mouth may be pulled obliquely, or the mouth may be stretched vertically.
This pattern is displayed after short, sharp pains, including sharp exacerbation of chronic pains, as when the doctor performs certain parts of the clinical tests for low back pain. The conclusion that this facial pattern indicates pain is supported by several lines of evidence:
Witnessing others displaying facial expressions of pain instigates unique patterns of brain activity associated in part with the direct experience of pain....2 (In non-scientific language, we feel each others' pain when it is displayed this way.)
Kenneth D. Craig and the co-authors of the chapter about facial display of pain in the Handbook of Pain Assessment state that [f]acial expression can largely be characterized as a reflexive, automatic reaction to painful experience, whereas verbal report is representative of a deliberate, controlled, and goal-oriented response to the event [that is, the stimulus].
3 They go on to state that discordance between the facial display and verbal report is most often observed during chronic pain, unless there is acute exacerbation.
I interpret this, together with the authors' lack of statements to the contrary, to mean that the facial display is not an accurate indicator of the intensity of chronic pain.
Facial pain displays are of special importance when working with infants or with cognitively-limited older patients. Researchers have developed facial pain grading techniques for newborns and premature babies.
Researchers in 1997 found that healthy four-to-six month olds who had been circumcised as neonates displayed a stronger facial pain response, cried longer, and were judged to have experienced more pain during vaccination than did non-circumcised boys. Boys who were circumcised with a topical analgesic tended to have an intermediate reaction.4
The response of little ones to pain changes rapidly as they develop. Several studies have found that while very young newborns respond to injections primarily with pain, infants at six to eight months first express fear, then pain, then anger.5 Good for them!
If we accept the authors' position that detailed FACS analysis of facial displays yields a superior measure of pain, what can we say about interpretation by un-aided observers? Studies have shown that health care workers estimate infant pain lower than family members do. Other studies have shown that observers including health care workers underestimate the pain of adults.6 Studies into the facial cues used by un-aided observers show that, although they use some of the same cues found effective in the FACS system, they don't “read” pain levels as well as the FACS system does. This can be seriously compounded by the use of published pain scales that use cues which aren't, based on the evidence, indicative of pain.7
If the facial display of pain is genetically-based, it is nevertheless subject to modification by learning and context. The facial expression of pain varies depending on the setting. Studies of audience effects suggest that people inhibit painful displays in the presence of strangers.
8 Notwithstanding, the authors state that children and adults can be relatively successful in faking, exaggerating, or suppressing facial displays of pain when it seems in their interests.
9 Experimenters have demonstrated that observers' readings tend to be more consistent with the impression that the subject wants to convey than with the subject's actual pain experience, and that observers are only marginally better than chance at detecting faked or suppressed pain. Faked or exaggerated pain tends to be "overblown," containing exaggerated versions of normal elements plus elements that are not normally present in facial pain. The authors say that the potential for misrepresentation is developed early in life. Interestingly, children appear less successful in deceiving their parents than do adults in deceiving one another, suggesting that skill in dissembling is acquired in the course of child development. The children were more adept at hiding pain than faking it....
10 (I'd be interested in knowing why children develop the capability of suppressing pain displays.)
Since detailed FACS-style analysis is impractical in the clinic but observers are easily deceived, the authors suggest a one-day training program which, they believe, allows clinicians to make more reliable pain judgments while they perform a lower back evaluation.