Harnessing the Smell of Fear

The release of “alarm molecules” is a subject has been well-researched and well-documented over the years. In Chapter 6 of Whiff!, we learn that “animals experiencing stress and fear produce chemical warning signals that can lead to behavioral and physiological responses in members of the same species. For instance, if a herd member were under attack, the animal would release a scented fear message to the others, warning the entire herd to flee as fast as dominoes may fall.” But what part of the olfactory system of the animal on the receiving end is responsible for detecting this crucial chemical message? The same component which allows them to perceive and identify odorants? Or maybe the vomeronasal organ which serves to detect sexual pheromones?

Neither, confirms a recently-concluded study from the University of Lausanne in Switzerland. It’s a third subsystem of the olfactory system, the Grueneberg ganglion, which is responsible for detection of “fear pheromones.” First identified in 1973 in the nose-tips of various mammals–including humans–this microscopic arrow-shaped group of nerve cells were ignored for decades until 2005, when biologist Marie-Christine Broillet began to suspect its connection to sniffing out fear, after electron microscopy revealed proteins associated with pheromone reception in mice.

Numerous tests and three years later, Broillet and her team have confirmed that the ganglion plays a crucial role in danger communication. When a group of mice with their Grueneberg ganglia removed and another group with their ganglia intact were exposed to alarm pheromones from stressed-out mice, the contrast was striking. The unaltered group displayed an immediate reaction, running to the corner of the box and freezing, while the ganglion-deprived group carried on as usual–oblivious to the chemical warnings. Both groups were still able to sniff out hidden cookies, demonstrating that their sense of smell was otherwise unaffected.

“This is a definite advantage for animals to have,” says Dr. Mathieu Lesort of the University of Alabama at Birmingham of the discovery, “because they are unable to make inferences about a situation using cues from their surroundings, as humans are able to do.”

But, why should humans rely on the sluggish, circuitous processing of visual and audio clues alone when this olfactory warning system–linked directly to our brains–works so much more efficiently?

We shouldn’t, and we don’t. Numerous studies have determined the human ability to distinguish “fear sweat” from “neutral sweat,” notably a 2002 experiment by Viennese research scientist Karl Grammer which demonstrated that women could detect the smell of fear in secretions from the armpits of people who had watched a terrifying film. But perhaps one of the most compelling examples lies in a remarkable but little-known rodent-like creature indigenous to East Africa.

Whiff! credits the recently-deceased Lyall Watson, author of Jacobson’s Organ, for spotlighting the Lophiomys which possesses a remarkably unique defense system: When alarmed, the animal secretes a volatile substance which renders any animal in the vicinity–including human beings–distinctly uneasy and fearful. This “little merchant of fear” is a small creature in a land of large predators, but is generally avoided–even though the olfactory illusion of danger is the only threat it has to peddle and there is, literally, nothing to fear but fear itself. If such potent alarm pheromones could be artificially reproduced, the potential for applications–from warning us to flee from pending earthquakes or terrorist attacks to dispersing crowds or evacuating buildings–fairly boggles the mind.

Dr. Broillet’s findings may be just the push needed to spur the additional research necessary to make these possibilities into realities. New studies are already being proposed to test how the ganglion intercepts and translates alarm signals to the brains of other mammals, including humans. It’s a fact not lost on Columbia University neuroscientist Stuart Firestein. “The study’s as significant for giving us so much to do,” he observed, “as it is for what it shows.”