The sense of smell doesn't get a lot of play in our current environment, but our ancestors likely used their noses in order to survive better in the wild. The ability to sniff out potential predators or rotten, disease-causing substances might have in many instances kept them alive. No surprise, then, that new research links a person's level of anxiety to a heightened sense of smell.

Researchers from University of Wisconsin at Madison exposed study participants to substances described as "neutral pure odor, neutral odor mixture, and negative odor mixture." They study participants were asked to detect whether an odor was present while in an MRI scanner. Researchers additionally measured skin conductivity and breathing patterns (two measures of anxiety), while also asking how anxious the participants was feeling. As levels of anxiety rose, so did the ability to discern negative smells. Researchers also found that, in response to negative odors, communication between the sensory and emotional areas of the brain increased.

Nature films often show zebras sniffing out lions, of course, but do we humans really get anxious over a whiff of spoiled milk? The research says yes, though the change in our emotional state might be imperceptible, as in a slight quickness of breath. Our olfactory environment has become more complicated than it might have been in earlier times, but the physical relationship between the input of negative stimulus and the anxiety response remains, a relic of evolutionary history that still serves us today.

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