Illness Clues From the Inside-Out

"We can detect subtle cues related to the skin, eyes and mouth. And we judge people as sick by those cues."
"[While there is some evidence that an unhealthy person emits odours another individual can identify as illness] the face is our primary source of social information for communication."
"People did not really become sick from [research-induced injections] the bacteria."
"The change of skin colour seemed to be the most robust [signal of illness]. We are trying to tap into these first cues."
John Axelsson, Karolinska Institute, Sweden

"[No one had studied whether humans can sense] experimentally induced sickness [by looking at faces]; sickness judgements turn out to be far more reliable [than other visual judgements -- gauging a person's personality from a neutral expression, as example]."
"We will be much better as other cues come into play, helping resolve any ambiguity. A sick person will likely become withdrawn from conversation and would hunch up."
David Perrett, psychologist, researcher, University of St. Andrews, Scotland

Can you spot the sick person? The face on the left shows a sick person and the right shows a healthy person. Audrey Henderson/St Andrews University

Judging from his comments Dr. Perrett, who was not involved in the Swedish research, is clearly intrigued with the findings of this new study published in the journal Proceedings of the Royal Society B. Dr. Axelsson makes a comparison between humans sensing illness in others and the evident capacity of other animal species to do just that with their 'more finely tuned disease radars', specifically those of odour.

Animals can sniff out sickness in other animals. One example, that of a Canadian hospital that undertook the assistance of an English springer spaniel trained to identify through smell bacterial spores that infect patients. There is evidence that dogs can be trained to sniff out the emergent presence of cancer cells. Evidence exists that in an unhealthy state, individuals emit odours which an alert other person can recognize as illness.

The research team that studied the thesis out of which their findings produced the recently published study was comprised of neuroscientists and psychologists in both Germany and Sweden. The team used a molecule found in bacterial membranes to inject eight men and eight women participating in their study with a view to examining their reactions. The injected substance, lipopolysaccharide, is known to elicit strong reactions in its presence from mammals and even insects.

The bodies of the test subjects would not know that the injected bacteria weren't attacking the body, and their immune systems reacted just as they were meant by nature to do, to eject the foreign substance. That reaction resulted in feelings of sickness on the part of the test subjects who were photographed two hours and ten minutes post-injection, coinciding with the time that most study participants stated they felt unwell. All of whom were photographed again, after  having received a placebo injection of saline solution on a different occasion.

The researchers then enlisted the reaction of sixty students recruited from Stockholm-located universities to assess the photographs. The portraits were examined by the students one after the other, with a sick face and a healthy face from the same individual appearing non-consecutively. Five seconds' time was allotted to view and assess each photograph, to identify the individual appearing in the photograph to be either healthy or ill, according to the viewers' perceptions.

On a scale of 0.5 to 1,0.5 representing completely random, the observers managed an average score of 0.62; the accuracy rate was judged to be well above sheer chance in correct observations. In three subject photographs the differences in healthy or ill appeared almost indistinguishable to the students, despite which the balance of 13 others were reliably and accurately judged as sick, (800 correct conclusions of the total 1.215 images presented).

Yet another group of 60 students was tasked to rate pale lips, droopy mouths or other possibly telltale features in the portraits -- resulting in skin colour being the most obvious symptom of an ill individual. Heavy eyelids also rated as an influential cue related to illness. The researchers noted that when observing a familiar face accuracy is heightened since one is familiar with normal colouration of a known individual's complexion.

Dr. Axelsson's considered opinion is that observing disease is a learned behaviour. And, of course, one might expect that those involved in the medical community, observing and diagnosing, would be most skilled at recognizing illness in the outward signs available on a face reflecting lack of wellness. Despite which, Dr. Axelsson plans to take his research one step further; to study whether indeed doctors and other medical professionals are more accurate in rating sick faces than untrained individuals.