November 6, 2012
Study Finds We Use Sense Of Smell In Emotional Communication
April Flowers for redOrbit.com - Your Universe Online
While is it well known that many species transmit information via chemical signals, the extent to which these chemosignals play a role in human communication is unknown. Researchers from Utrecht University in the Netherlands have investigated whether we humans might actually be able to communicate with each other about our emotional states through chemical signals.
Previous studies have suggested that emotional expressions serve more than one function. For example, fear signals not only help to warn others about environmental danger but are also associated with certain behaviors that offer a survival advantage through ℠sensory acquisition´ to the individual that emits them.
Previous research has revealed that making a fearful expression, like opening the eyes very wide, leads us to breathe in deeply through our noses, enhances our perception, and accelerates our eye movements. This in turn allows us to spot potentially dangerous targets quickly. Disgust reactions, known as ℠sensory rejection´, warn others to avoid potentially noxious chemical by lowering our eyebrows and wrinkling our noses.
Building on this research, the research team examined the role of chemosignals in social communication. The underlying hypothesis is that chemicals in bodily secretions, such as sweat, activate processes in both the sender and the receiver, establishing a sort of emotional synchrony between them.
In other words, this means that people who inhale chemosignals associated with fear would then make a fearful expression themselves, showing signs of sensory acquisition. People who inhaled chemosignals associated with disgust would likewise make an expression of disgust, showing signs of sensory rejection.
The team collected sweat from men while they watched either a disgust-causing or a fear-causing movie. To avoid possible contamination, the men followed a strict protocol for two days prior to the collection; they did not smoke, engage in in excessive exercise, or consume odorous food or alcohol. The protocol also called for the participants to use scent-free personal-care products and detergents that were provided for them.
The sweat samples were then exposed to women while they were performing a visual search task while their facial expressions were recorded and their eye movements were tracked as they completed the task.
As predicted by the team, women who were exposed to chemosignals from "fear sweat" produced fearful expressions. Likewise, women exposed to chemosignals from "disgust sweat" exhibited facial expressions typically associated with disgust.
Additionally, the researchers also found that the chemical signals of fear and disgust altered the women's perceptions during their visual search task. These signals also changed the sniffing and eye-scanning behaviors in accordance with either sensory acquisition or sensory rejection. Moreover, the changes appeared to be unconscious as the women reported that they were not aware that they had shifted their behavior. There seemed to be no relationship between the effects observed and how pleasant or intense the women judged the stimuli to be.
The authors argue that these findings are important because they contradict the common assumption that human communication is solely through language and visual cues. Instead, the findings support the embodied social-communication model, which suggests that chemosignals act as a medium through which people can be "emotionally synchronized" on a level that is outside of their conscious awareness.
These effects could also help to understand the kind of emotional contagion that is often observed in situations involving dense crowds, such as mob riots.