Smell a rat? Yes! But can you smell disgust? Probably. On the contrary, the amazing range of ways animals transmit information to each other through chemical signals—like territorial marking, odour trail formation, mate attraction—doesn’t surprise us. But we would be surprised to know chemosignals indeed play a role in human communication.
Existing research suggests that emotional expressions are multi-faceted, serving more than one function. Fear signals, for example, not only help to warn others about environmental danger, they are also associated with behaviours that confer a survival advantage. A key mechanism to confer this advantage is heightening our senses–so that we breathe in more through our noses and accelerate our eye movements so that we can spot potentially dangers quicker. Disgust signals, on the other hand, help us to avoid potentially noxious chemicals and diminish our senses, causing us to lower our eyebrows and wrinkle our noses.
Researchers from Utrecht University investigated whether we humans might actually be able to communicate our emotional states to each other through chemical signals.
They conducted a test to examine the function of chemosignals in a framework furnished by embodied social communication theory.
The experimenters collected sweat from men while they watched either a fear-inducing or a disgust-inducing movie. The men followed a strict ‘no smoking, consumption of scent-free products’ protocol to avoid possible contamination
Women were then exposed to the sweat samples while performing a visual search task. Their facial expressions were recorded and their eye movements were tracked as they completed the task.
As the researchers predicted, women who were exposed to chemosignals from “fear sweat” produced fearful facial expressions, while women who were exposed to chemosignals from “disgust sweat” produced disgusted facial expressions. The researchers also found that exposure to fear and disgust sweat altered the women’s perceptions during the visual search task and affected their sniffing and eye-scanning behaviors in accordance with either sensory acquisition or sensory rejection
These findings underline the common assumption that human communication occurs exclusively through language and visual cues. Rather it suggests that chemosignals act as a medium through which people can be “emotionally synchronised” outside of conscious awareness.