Throughout human evolution, infectious diseases have been the leading cause of death.
The detection of subtle signals indicating disease and leading to the avoidance of sick people would, therefore, be an adaptive way of coping with an environment full of pathogens.
DISCOVERY OF A HUMAN BRAIN CAPACITY AND ITS FUNCTIONS
The human brain is much more powerful than we thought. He would be able to discover and avoid diseases that affect people in our environment, according to a new study conducted by Karolinska Institute researchers in Sweden.
Our sense of vision and smell are enough to make us realise that someone has a disease before it even declares itself. And not only conscious – we also act on the information received and avoid sick people. This study (with surprising results) has been published on May 22, 2017, in the scientific journal PNAS.
THE BRAIN DETECTS DISEASES IN OTHER PEOPLE AT AN EARLY STAGE
The human immune system is effective in fighting the disease, but since it involves a large amount of energy expenditure, avoidance of the disease should be part of our survival instinct.
This new study now shows that this is indeed the case: the human brain is better than previously thought to discover an early stage disease in people around us. In addition, we also tend to act on signals by presenting less healthy people to infected people.
” The study shows us that the human brain has great abilities and that this discovery motivates avoidance behaviour, “ says lead researcher Mats Olsson of the Department of Clinical Neurochemistry at the Karolinska Institutet. Recall that avoidance is a defence mechanism against anxiety already identified by science.
ONE OF THE LAST MYSTERIES OF THE BRAIN REVEALED
By injecting innocuous layers of bacteria, researchers activated the immune response in participants, who developed the classic symptoms of the disease – fatigue, pain and fever – for a few hours. Odour samples were taken, photographed and filmed. The injected substance then disappeared from their bodies and with it the symptoms!
Another group of participants was then exposed to these odours and images as well as those of the healthy controls. Participants were asked to rate how many people they enjoyed while their brain activities were measured by a CT scan (magnetic resonance imaging, MRI).
They were then asked to identify, by looking at the photographs, the participants who looked sick, the people they considered attractive and those they might consider contacting.
” Our study shows a significant difference in how people prefer and are more likely to get in contact with healthy people, than those who are sick and whose immune system we have artificially activated,” says Professor Olsson.
” We can also see that the brain is performing to add weak signals from multiple senses related to a person’s state of health in our environment .” It considers biological confirmation of the argument that survival naturally means avoiding infection.
” Common sense tells us that there should be a basic repertoire of behaviour that helps the immune system.Avoiding, however, does not necessarily apply if you have a close relationship with the person
who is sick, “says the study. ” For example, there are few people other than your kids that you kiss when they have a runny nose. In other words, a disease signal can improve the management behaviour in close relationships. With this study, we demonstrate that the brain is more sensitive to these signals than previously thought. “