By Alison George | NewScientist.com

From politics to commerce to sex, the "forgotten emotion" of disgust can affect you in subtle ways

David Pizarro can change the way you think, and all he needs is a small vial of liquid. You simply have to smell it. The psychologist spent many weeks tracking down the perfect aroma. It had to be just right. "Not too powerful," he explains. "And it had to smell of real farts."

It’s no joke. Pizarro needed a suitable fart spray for an experiment to investigate whether a whiff of something disgusting can influence people’s judgements.

His experiment, together with a growing body of research, has revealed the profound power of disgust, showing that this emotion is a much more potent trigger for our behaviour and choices than we ever thought. The results play out in all sorts of unexpected areas, such as politics, the judicial system and our spending habits. The triggers also affect some people far more than others, and often without their knowledge. Disgust, once dubbed "the forgotten emotion of psychiatry", is showing its true colours.


Disgust is experienced by all humans, typically accompanied by a puckered-lipped facial expression. It is well established that it evolved to protect us from illness and death. "Before we had developed any theory of disease, disgust prevented us from contagion," says Pizarro, based at Cornell University in Ithaca, New York. The sense of revulsion makes us shy away from biologically harmful things like vomit, faeces, rotting meat and, to a certain extent, insects.

Disgust’s remit broadened when we became a supersocial species. After all, other humans are all potential disease-carriers, says Valerie Curtis, director of the Hygiene Centre at the London School of Hygiene and Tropical Medicine. "We’ve got to be very careful about our contact with others; we’ve got to mitigate those disease-transfer risks," she says. Disgust is the mechanism for doing this - causing us to shun people who violate the social conventions linked to disgust, or those we think, rightly or wrongly, are carriers of disease. As such, disgust is probably an essential characteristic for thriving on a cooperative, crowded planet.

Yet the idea that disgust plays a deeper role in people’s everyday behaviour emerged only recently. It began when researchers decided to investigate the interplay between disgust and morality. One of the first was psychologist Jonathan Haidt at the University of Virginia in Charlottesville, who in 2001 published a landmark paper proposing that instinctive gut feelings, rather than logical reasoning, govern our judgements of right and wrong.

Haidt and colleagues went on to demonstrate that a subliminal sense of disgust - induced by hypnosis - increased the severity of people’s moral judgements about shoplifting or political bribery, for example (Psychological Science, vol 16, p 780). Since then, a number of studies have illustrated the unexpected ways in which disgust can influence our notions of right and wrong.

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