The trolley problem: would you sacrifice one life to save five lives?The trolley problem: would you sacrifice one life to save five lives?

Paul Kaufman, chair of the East London Humanists, explains the concept of disgustology, a new area of research which explores the pivotal role of revulsion in the evolution of human morality.

Disgustology has been coined to describe what is a relatively new area of research. The study of revulsion, a uniquely human emotion, raises important questions about how we make moral decisions. Thought-provoking results from various experiments about our 'disgust' response have recently featured in the press. One example involved asking participants about cleaning their bathroom with a cloth bearing the national flag. Conservatives are more likely to say this is wrong and disrespectful; left-leaning liberals are less likely to be concerned about the 'sanctity' of a piece of cloth.

As an evolutionary psychologist, Dr Diana Fleischmann explores the evolution of the human mind in much the same way as an evolutionary biologist explores the evolution of the human body. She argues that the role played by the disgust emotion is unique. It was an adaptation humans developed in response to the threat of disease, for example, to avoid eating meat crawling with maggots. She believes this adaptation, originally developed for self-preservation, now influences our moral judgements in ways which are not always rational.

A feeling of repugnance is often treated as sufficient evidence that the behaviour that causes this reaction is wrong. This avoids dealing with a possible lack of rational argument against the offending behaviour. One of many examples is the response to other people's sexual practices. Another is stem cell research. Dr Fleischmann quotes from a religious conservative and adviser to George Bush, who opposed this valuable scientific development, with the words: "Shallow are the souls who have forgotten how to shudder."

Dr Fleischmann views the 'misfiring' of disgust as a potential weakness, or bias, in our evolved morality, and one we should be mindful of. It helps to explain why humans often make decisions which are rationally less ethical to avoid committing an act that causes them moral disgust. This is illustrated by classic dilemmas such as the so-called 'trolley problem.' In this thought experiment, a run-away trolley is about to run over five people tied to the railway tracks. Many people would not wish to pull a lever diverting the trolley to a parallel track on which one person is tied up. Their disgust at being responsible for taking one life outweighs the logical decision, which would save five lives.

Dr Fleischmann doesn't provide any easy answers. However, the questions she raises are fascinating. At our meeting this month, we will show a film of The Darwin Day Lecture 2018, given by Dr Fleischmann and chaired by Jim Al-Khalili, scientist, broadcaster and vice-chair of Humanists UK. There will be plenty of time for questions, answers and discussion afterwards.

The East London Humanists' discussion on disgustology will take place at Wanstead Library on 23 April from 7.30pm (visitors welcome; free). Visit wavidi.co/elh

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