Illustration for article titled Is your immune system controlling how you feel about this person?

Were you recently sick? If so, newly published research says you're more likely to be repelled by "disfigured" faces like the one up top. The findings provide the very first evidence of how a biological immune response can actually give rise to a psychological immune reaction — and this backs up recent research that points to an adaptive interaction between our psychological and biological systems.


Every relatively healthy person has their very own biological immune system (BIO). You know: T-cells, B-cells, all that good stuff. But you've also got what scientists refer to as a "behavioral immune system" (BEH). Your BEH is what tells you to step away when you see that your toddler cousin is about to wipe snot all over your face, or to turn and run when you see a zombie lurching your way.

Recently, scientists have shown that activation of your BEH can lead to heightened levels of biological immune response (for example, the observation of skin lesions on another person can lead to an increase in your own production of B-cells).


Now, University of Kentucky psychologist Saul Miller has teamed up with Florida State University's Jon K. Maner to demonstrate for the first time that the opposite cause and effect — wherein the activation of your BIO system leads to activation of your BEH system — can also occur.

In one experiment, volunteers were shown a series of faces, some disfigured (e.g. lesioned, or distorted in a pre-sneeze grimace) and some normal, on a screen. Following the appearance of each face, a circle or square would appear, and the test participant would have to indicate which shape had appeared as quickly as possible by pressing a button corresponding to the shape. A longer delay between the time it took for the volunteer to shift attention to the shape and select the corresponding button meant the participant had paid closer attention to the face.

After the face/shape test, volunteers were asked whether they had been ill recently. The researchers found that the more recently a volunteer had been ill, the more likely he or she was to pay more attention to disfigured faces than to normal faces. Those who had not been ill reacted just as quickly after seeing a disfigured face as they did after seeing a normal one.

In a second experiment, volunteers were shown a disfigured face or a normal face, and asked to respond by pushing a joystick in response to the type of face that appeared; participants were instructed to push the joystick away from them (indicating avoidance) in response to disfigured face, and pull towards them (indicating approach) in response to a normal face.


While all the volunteers tended to push the joystick away faster than they pulled, recently sick volunteers were shown to do so significantly faster than the recently healthy. Moreover, the researchers observed that the sicker a volunteer had been, the faster they tended to push.

"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" said Miller, who hypothesizes that the recently ill likely interpret these visual cues as a sign of contagion.


The researchers write:

The current findings provide important insight into the ways in which humans evolved to overcome disease threats. Combined with recent findings indicating that BEH system activation facilitates BIO system activation, the current findings suggest a bi-directional and compensatory relationship between the BIO and BEH systems. This relationship likely exists to provide maximal protection against infection when disease threats are most threatening; if one system fails (e.g., the BIO system is weakened), the other system provides an alternative solution (e.g., avoiding potential sources of contagion). Thus, the current findings illuminate a potentially adaptive interaction between psychological and biological systems.


The researchers' findings will appear in this month's Psychological Science; a direct link to the study will be made available when the article goes live.

Thanks to Dr. Saul Miller for the advance copy of the research paper

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