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“That stinks.”

“Rotten to the core.” 

“It makes me sick.”

“I can’t stomach it.”


We’re all familiar with these visceral metaphors that convey disgust. But next time you hear such words, be curious about that mucky pile of yuck because beneath all that disgust lies a violation of a fundamental norm of human interaction: fairness.


Why is unfairness disgusting? 

Why does unfairness initiate such an intense emotional and physical response that its effects can last for days, or even decades?


For answers, we need to go back into our evolutionary past to understand how fairness, and the related concepts of trust and reciprocity, have imprinted so deeply on our psychology and physiology.


Before bank accounts and supermarkets, our mental trading ledgers kept track of people’s exchange behaviours. Favours - such as shared food resources - were essentially stored in other people. This system only worked if people acted fairly and had an ability to recognise reciprocal behaviour in others. So much so, that the ability to detect fairness and unfairness, was selected for as an evolutionary trait conferring advantage.


Fairness is a primary and primal human need.

We are as attracted to fairness as we are repulsed by unfairness.

Fairness evolved as a reward; unfairness evolved as a threat.

Embodied, visceral, real.


Gustatory (taste) disgust and social disgust are processed in the same brain region: the insula, part of the limbic system involved in emotional and behavioural response. Rancid food stimulates a cascade of physiological responses evolved to protect us from toxins and pathogens. Rancid behaviour that violates the social norms of fairness and morality, activates a similar visceral response. Just contemplating the moral disgust of an unfair act leaves us with both a literal and metaphorical bad taste in our mouths such that our perception of taste is altered accordingly.


Gustatory reward and social reward are also processed in the same brain region: the ventral striatum, an area linked to the dopaminergic reward system and involved in motivation and motor responses. The striatum receives a dopamine stimulus both when we eat fresh nourishing food and when we experience the social reward of fairness. This stimulates a ‘move towards’ response, creating a positive reinforcement effect. Fairness is its own reward.


And fairness is a beautiful thing. So says the Old English origin of the word ‘Faeger’, meaning beautiful, attractive and pleasing to the eye. Through Middle to Modern English, the meaning of fairness shifted away from attractive appearances and towards attractive qualities such as justice, equality, impartiality and transparency.


The norms of fairness have been reinforced by rules as our scales of interaction became more complex over time. For example, justice systems encourage and enforce fairness by punishing unfair acts. We talk of level playing fields, even-handedness and balanced scales to convey the abstract but highly regarded concepts of equality in opportunity and treatment.


Treating people fairly, sets up an expectation that you, in turn, would also be treated fairly. Hence, the prevalence of the ‘Golden Rule’, and its equivalents in religion and philosophy: Treat others as you would have them treat you.


Understanding the biological and psychological bases of fairness and how we express these through language offers new perspectives and pathways for changemakers. If you hear words of disgust, look beyond the language for the root cause. Is there a transgression of fairness at play?


Changemakers can leverage our shared human need for fairness in campaigns and through advocacy. In Australia, for example, we have a deep cultural understanding and agreement about the “fair go”. It encodes the intrinsic values of equality, broadmindedness, friendship and social justice that most people are motivated by. Our shared embodied understanding of fairness enables us to activate empathy and engage people in bigger-than-self thinking via the ultimate question: how would this feel if it were you?



Go Deeper


Chapman H. A. (2009). In bad taste: evidence for the oral origins of moral disgust. Science 323,1222-1226.


Chapman H. A. & Anderson A. K. (2013). Things rank and gross in nature: A review and synthesis of moral disgust. Psychological Bulletin 139, 300-327.


Eskine K. J., Kacinik N. A. & Prinz J. J. (2011). A bad taste in the mouth: gustatory disgust influences moral judgment. Psychological Science 22, 295-299.


Rock D. (2009). Your Brain at Work. HarperCollins.


Sapolsky R. (2017). Behave. The Biology of Humans at our Best and Worst. Penguin Random House.

© Words for Change

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