While most appreciate the efficiency of our immune system — a biological system that automatically responds to pathogens once they have entered our system — few realize that our brain also has an immune system.
In fact, our behavioral immune system can activate our physiological immune system when the brain perceives threats.
A new study takes this a step farther and presents evidence that recent bouts of illness will cause a heightened sense of awareness of potential threats that may cause a repeat bout of illness and cause avoidance behavior.
“When people have been recently sick, and therefore recently activated their physiological immune systems, they are more likely to pay attention to and display avoidance of disfigured faces”—which they read, like a rash or a sneeze, as a sign of contagion, said University of Kentucky psychologist Dr. Saul Miller.
Two experiments showed that the recently ill more vigilantly pay attention to and avoid others who might make them sick.
In the first, faces, some disfigured and some normal, were displayed on a screen. When they disappeared, either a circle or square appeared, and the person had to press a key, as quickly as possible, indicating which shape they saw.
When the face appeared in a different portion of the screen, the participant had to shift her attention to it. A longer lag in switching meant more attention was paid to the face.
After 80 trials, participants answered a questionnaire about whether they had been ill—”feeling a little under the weather,” “had a cold or flu recently,” for instance—and if so, when, from today to a year or more ago.
Other questions measured feelings of vulnerability to disease and germs.
The results: Independent of their conscious worries, those who had more recently been ill paid more attention to the disfigured faces than to the normal faces. Those who hadn’t been ill showed no difference in reaction time.
In the second experiment participants had to push a joystick—a tested indication of avoidance—in response to a disfigured face and pull (showing approach) for normal face.
Everyone was quicker to push away the disfigured one or pull the normal one. But those who’d been sick were even quicker than normal in avoiding the “sick” face, and the sicker they’d been, the faster they pushed. The not-ill people showed no difference.
Researchers believe these findings tell us something about human nature and may teach us something about reducing bigotry, racism and segregation.
“When we’re sick, we tend to show biases against people stereotypically associated with disease—the obese, the elderly, foreigners,” says Miller.
Avoiding people who might make us sick is hard-wired behavior when we ourselves our ill, he says.
But we’re taught to be repelled by certain people—like the obese, old, or foreign—who present no threat of contagion.
While scientists learn the pathways between psychological and physiological immunity, he suggests, the rest of us can unlearn our fears and treat people better.