Smell of Fear

Recent studies done at Rice University may have found that the "smell of fear" may be more than just an old saying. Denise Chen of Rice's psychology department has recently published work showing that humans may in fact react to the smells emitted by frightened humans in their surrounding.

One of the many ways in which organisms communicate with one another is through the use of
"pheromones". Hormonal chemicals emitted outside the body to relay messages to other members of the same species. Biologist E.O. Wilson discovered in the 1960s that ants taste and smell substances that evaporate from the chemicals laid down by other ants. When threatened ants will release alarm pheromones into the air that expand in a circle of smell. Ants can then determine the concentration of the pheromone to determine the proximity of the source of danger.

Dr. Chen, speculated that humans may have a similar mechanism in sweat, and so to test this hypothesis researchers collected sweat samples from male subjects watching a series of horror films. These samples were then slipped under the nostrils of female volunteers as they viewed a series of faces with happy to ambiguous to fearful facial expressions. The women were then tasked to indicate whether the face was happy or fearful on a computer.

Researchers found that the women subjects exposed to the smell of fear were unaffected in their interpretations of discernible facial expressions, but showed a bias towards "fearful" when it came to the ambiguous. As Dr. Chen explains of the findings, “Our findings provide direct behavioral evidence that human sweat contains emotional meanings and that social smells modulate vision in an emotion-specific way."

While further research is needed into the impacts of smell on emotional processing, it does provide added evidence of the prevalence of the sense of smell in human function; especially when the more dominant senses are weak.

Sources:

http://www.sciencedaily.com/releases/2009/03/090306142536.htm