Yes, it's official. Cooties exist:
This may be the first study, though, that reveals an evolutionary basis to shopping preferences. Low-threshold revulsion makes sense, protecting our ancestors from eating rotten or poisonous food or touching animals that had died of infectious disease. The face of disgust--with the nose wrinkled and the eyes squinted as if against some pungent smell, and the tongue often protruding as if spitting something out--tells you a lot. "It was probably," says Fitzsimons, "a pretty good proxy for the germ theory of disease before anyone knew germs existed."
Strong preferences were just what the subjects exhibited. Any food that touched something perceived to be disgusting became immediately less desirable itself, though all of the products were in their original wrapping. The appeal of the food fell even if the two products were merely close together; an inch seemed to be the critical distance.
Notice that the first response regarding this research is to immediately link it to evolution, but not in a way that actually explains why this emotional response developed.
The author talks briefly about the germ theory, as noted in this quote, but the actual thing being tested here is the emotional response to objects.
If we were truly rational creatures, then the proximity of objects to each other would truly make no difference at all. We would acknowledge the wrapping around the foods and realize that no contamination was possible.
But we are not always rational creatures. I would find it to be a better study to develop this into discerning why we are not more rational in our approach to objects. But the focus is instead turned to marketing and improving the chances of redirecting the almighty dollar to one company's product instead of the competitor's.