The Smell of Fear: It's Catching

How good is the human sense of smell? Smell provides us with information about our environment, but due to evolution plays second string to our more developed senses of sight and hearing. Cortical areas in our brains are more devoted to cognitive, visual, and auditory functioning, while other species, such as rats and dogs, have increased area in their brains devoted to the sense of smell (relative to their brains' total sizes). Despite our more significant dependency on our other senses, we can actually identify a variety of scents, each discriminated by a specific and intricate combination of chemicals to our olfactory receptors. While humans can get by just fine without a sense of smell, it adds a descriptive component to everyday life that would surely be missed by those of us who have it. Smell plays the role of a warning system, alerting us of dangers such as spoiled food or a fire, and that of an enhancer, supplying yet another quality to associate an object or experience with. Close your eyes and imagine waking up in the morning to the aroma of hot coffee, the fragrance of apple pie for dessert, or an attractive perfume on your date. It is not hard to believe that the areas of our brain connected to smell are closely related to those involved with memory formation. We tend to rely more on smell when our other senses are weak, as opposed to animals that depend on a more sophisticated olfactory system as a sense of direction and communication. With our slightly inferior noses, is it credible for humans to identify scents characteristic of things less tangible than food, smoke, or cologne…such as emotion?

According to several studies, humans can actually smell the emotion of fear (staying true to the theme for Halloween). This discrimination occurs at a subconscious level, influencing our interpretation of otherwise ambiguous situations as fearful ones. What is the source of this smell? Human sweat. "Our findings provide direct behavioral evidence that human sweat contains emotional meanings," said Denise Chen, a psychologist at Rice University in Houston. Supposedly, we are able to unconsciously detect whether or not someone is stressed/fearful via the release of a chemical pheromone through his/her sweat. Brain regions of the study participants associated with fear (the amygdala and hypothalamus) responded at stronger levels when the smell inhaled was of sweat collected from the armpits of petrified skydivers vs. sweat collected from exercisers. However, participants did not posses the ability to consciously distinguish between the two types of sweat.

This leads scientists to believe that emotions may in fact be contagious via a process of chemical transfer, adding a whole other component to social dynamics. Imagine the appeal to military institutions hoping to invoke fear in enemies, or perfume companies working to master the rules of sexual attraction (yes, there are pheromones in sweat during sex as well). Movie directors of horror films perhaps profit from this, because if one person in the movie is scared, chances are the viewers immediately around him will sense fear, starting a domino effect. The marketable value of these research results suggests a way in which pheromones may physiologically influence our behavior and perception. So the next time that you have an exam, remember not to show up too early with all of the worriers; just being around them can create a source of self-doubt when confidence is necessary to perform well.

For more information on two of these studies, click the links below:

http://www.livescience.com/health/090310-fear-scent.html

http://www.guardian.co.uk/science/2008/dec/04/smell-fear-research-pheromone