Emotions may bend your moral values.

Neuroscience offers a biological point of view to moral dilemmas.

Deciding between green tea and black tea is a straightforward problem and has effectively no implications. However, deciding on a moral issue is problematic; outcomes frequently involve significant loss (e.g. death penalty), and we struggle to assign value to its elements (e.g. what is the value of a life?). We cannot ignore these questions, but we can recognise that emotions influence the brain’s decision-making process and shape our moral judgement.   

Are you feeling disgusted?

Disgust is an emotional response of rejection of certain substances. In a world full of parasites, microbes and viruses, disgust has evolved as a mechanism that helps species to avoid eating contaminated food. For example, dead meat has a high bacterial load and can cause food poising [1]. The British Journal of Nutrition has published an article on how bacterial endotoxins survive the cooking process and then increase inflammatory reactions in our body [2].

Although the brain processes disgust to prevent food poisoning, there is evidence to suggest it extends the same mechanism to social rejection. Researchers have shown that humans use words and facial expression, demonstrating disgust to socially inappropriate behaviour, such as cannibalism, torture, hypocrisy or betrayal [3].

Shifting moral judgement.

Researchers investigated whether participants’ opinion change under different disgusting conditions; physical (a putrid smell, a dirty room) and psychological (by recalling a physically repulsive experience, watching a video) [4]. Then compared the answers with those of participants in the control group (a clean and tidy environment). Examples of moral tests involved illustrations (a man eating his dog and a plane crash survivor eating dead passengers) and public policy (spend money on patrolling borders against illegal immigrants).

Interestingly, participants in a disgusting environment had a significant increase in the severity of their moral judgements relative to those in a clean room and displayed bodily reactions, such as nausea. This means that when feeling disgusted participants strongly judged the man eating his dog and were more supportive of public policies involving more control against illegal immigrants. Whereas those in a clean and tidy room, thus less disgusted, demonstrated more acceptable moral judgement.

These results suggest that moral judgement associated with disgust shifts according to the environment (e.g. how clean is your city, home, workplace). More importantly, it may be possible to deliberate induced the concept of disgust using a technique called priming (e.g. advertisement and campaigns).

The neuroscience behind it.

It is fascinating to see that individuals who have rated moral dilemmas as more acceptable have neurons spiking on different areas of the brain compared to the neurons from their morally strict individuals [5]. How do we know that? Neuroscientists have used a brain scan, called functional magnetic resonance imaging (fMRI), and detected significant changes in brain activity in the frontal lobe of the brain. Interestingly, the frontal lobe is know for processing key intellectual functions such as decision-making, planning and judgement.

Furthermore, the association between emotions (disgust) and decision-making (moral judgement) is consistent with Damasio’s Somatic Marker Hypothesis. You might recall that just by thinking the brain triggers emotions (e.g. disgust) and bodily reaction (e.g. nausea), thus influencing the ability to make decisions.

A neuropharmacological test showed that healthy volunteers who took citalopram (a selective serotonin inhibitor, like an anti-depressive drug) promoted more prosocial behaviour than those who received a placebo drug [6]. This means that the neurotransmitter serotonin, increase prosocial behaviour, thus moral judgement. Fun fact: the production of serotonin requires an amino acid, called tryptophan, found in sesame seeds.

Stress also influences moral judgement.

I hope it is not a surprise to tell you that psychological stress also affects moral judgement. There is evidence that activation of the stress response inclined individuals to fewer utilitarian responses when faced with ethical questions [7]. Utilitarianism is a concept that proposed every act should maximise the good and wellbeing to the largest number of people [8].

As you might remember from my previous post, stress is also a survival mechanism and triggers physiological functions to ensure survival. We could say that the stronger the perception of threat and danger, the more individualistic you become. Given the theory of natural selection, I am not surprised to have reached this conclusion.

However, bear in mind that we often feel threatened at work by peers and supervisors or in relationships by our friends and partners who have symptoms of anxiety and stress. As a result, we may display individualist behaviour rather than providing support and care.


Look around and make an honest evaluation about the environment you spend most of your time—probably your home, work and commute— but do not forget the places you often go to have fun and meet your friends (pub, cinema, gym). How clean (or dirty) are these places? How likely are you to discuss moral dilemmas in those places? Do you feel threatened by someone around you? How do you think the environment you live affects your moral judgement? 

Last, but not least, here is a list of significant moral dilemmas we face today. Perhaps you could test someone you know by asking their opinion about these dilemmas in different places. (a) should we edit children’s genome? (b) should we give robots the right to kill? (c) is it ethical to profit from livestock farming? (c) is it wrong to be a whistle-blower? (d) should governments provide universal basic income to its citizens? (e) if all humans are the same, then why do we need borders? 


There is evidence to suggest that emotions, such as disgust, can trigger bodily reactions, which shift our moral judgement. Also, the environment plays a crucial role in how we feel and subsequently make decisions. Last, these facts are consistent with neurobiological research and the somatic marker hypothesis.

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[1] Greger, M. (2012, July 6). Dead meat bacteria endotoxins. Retrieved from Nutritionfacts.

[2] Erridge, C. (2011). The capacity of foodstuffs to induce innate immune activation of human monocytes in vitro is dependent on food content of stimulants of Toll-like receptors 2 and 4. British journal of nutrition, 105(1), 15-23.

[3] Haidt, J., Rozin, P., McCauley, C., & Imada, S. (1997). Body, psyche, and culture: The relationship between disgust and morality. Psychology and Developing Societies, 9(1), 107-131.

[4] Schnall, S., Haidt, J., Clore, G. L., & Jordan, A. H. (2008). Disgust as embodied moral judgment. Personality and social psychology bulletin, 34(8), 1096-1109.

[5] Lim, J., Kurnianingsih, Y. A., Ong, H. H., & O’Dhaniel, A. (2017). Moral judgment modulation by disgust priming via altered fronto-temporal functional connectivity. Scientific reports, 7(1), 10887.

[6] Crockett, M. J., Clark, L., Hauser, M. D., & Robbins, T. W. (2010). Serotonin selectively influences moral judgment and behavior through effects on harm aversion. Proceedings of the National Academy of Sciences, 107(40), 17433-17438.

[7] Youssef, F. F., Dookeeram, K., Basdeo, V., Francis, E., Doman, M., Mamed, D., … & Legall, G. (2012). Stress alters personal moral decision making. Psychoneuroendocrinology, 37(4), 491-498.

[8] Sinnott-Armstrong, W. (2019, June 3). Consequentialism. Stanford Encyclopedia Philosophy. Retrieved from Stanford.

Image by Matt Warring

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