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Psychology: The appetite for right

John Whitfield explores two studies that take us from infant ethics to moral choices faced by adults in society.

Just Babies: The Origins of Good and Evil

Crown: 2013. 9781847921628 | ISBN: 978-1-8479-2162-8

Moral Tribes: Emotion, Reason, and the Gap Between Us and Them

Penguin: 2013. 9781594202605 | ISBN: 978-1-5942-0260-5

It would be nice to think that ideas of right and wrong were founded on a blend of insight, experience and instruction. But mostly, instinct is in charge. Morality is an appetite for certain types of behaviour in oneself and others. Like tastes in food and sex, it is rooted in biology, shaped by culture and imperfectly controlled by reason.


As with those other appetites, we develop moral urges because our ancestors prospered by heeding them. Morality underpins social life by guarding against the selfishness that threatens cohesion, and turning that togetherness into a weapon against outsiders. But ethical instincts that put 'us' before 'them' are poorly suited to a globalized world in which different moral systems are in constant contact and problems such as climate change demand cooperation on an unprecedented scale.

Psychologists Paul Bloom and Joshua Greene share this view of the evolutionary roots, social function and limitations of morality. They diverge, however, on the aspects of it that they tackle.

In Just Babies, Bloom looks at how moral psychology develops in childhood. Using puppet shows or animations that depict helpful or antisocial behaviour, researchers are probing how the ability to judge others develops in infants. These studies, many of which are the work of Bloom and his colleagues, show that ideas of right and wrong begin to emerge so early in life that they must be innate: three-month-olds show that they recognize and prefer good deeds by, for example, looking longer at a kind character than a mean one.

Bloom, ever brisk and authoritative, generally focuses on how things are rather than on how developmental psychology might inform philosophy. His discussion of disgust is particularly good. This is partly because the experiments he describes are nifty. Moral purity, for example, is a value associated with conservative philosophies, and students' political views have been shown to move rightwards when they are standing next to a hand-sanitizer dispenser. And it is partly because he pursues the implications further, arguing that disgust is a poor guide to right and wrong and is liable to make people prejudiced and abusive.

In two senses, Greene picks up where Bloom leaves off. Moral Tribes looks at how adults resolve ethical dilemmas, and makes a detailed case for how they should do this.

Greene argues that we have two moral systems that engage different parts of the brain. A fast, automatic, 'tribal' one operates through the emotions and is well suited for solving problems within groups; a slower, deliberative one allows a more impartial perspective. This echoes ideas in Daniel Kahneman's Thinking, Fast and Slow (Farrar, Straus and Giroux, 2011); the relevant bit of Greene's book is even called 'Morality Fast and Slow'. Greene's research has focused on conflicts between the two systems, using a philosophical problem called the trolley dilemma, which asks whether it is right to put one person in the path of a runaway tram to save the lives of several more. Most people believe it is wrong to stop the trolley by pushing a man onto the tracks. But most think it is right to flick a switch that diverts the car from a track on which it hits five people onto one where it hits only one.

This seems like an instinctive manifestation of the doctrine of double effect — the philosophical principle that holds that using people as a means to an end is worse than harming them as collateral damage. Greene's experiments, however, seem to show that we think that flicking a switch is more ethical than pushing a person not because of any moral distinction, but because it is socially useful to recoil from physical violence that might provoke retaliation or ostracism.

In place of moral absolutes, Greene carries a flag for utilitarianism. This pragmatic philosophy, developed in the eighteenth and nineteenth centuries by Jeremy Bentham and John Stuart Mill, argues that, to quote Bentham, “it is the greatest happiness of the greatest number that is the measure of right and wrong”. The brain's slow moral system, Greene says, naturally arrives at utilitarian decisions, and the philosophy's universality and impartiality transcend faster 'tribal' thinking.

As a science writer who touches on issues beyond science, Greene should be cherished for pursuing his questions wherever they take him and for having the interdisciplinary skills to do so. Moral Tribes is clever and absorbing. But although Greene makes a persuasive case for utilitarianism as a means for individuals to live a good life, there is a politics-shaped hole in his suggestion that it might offer a cure for social divides.

It is difficult, for example, to imagine pro-lifers being swayed by Greene's utilitarian argument for the legality of abortion — as the satirist Jonathan Swift remarked, you cannot reason a man out of something that he was not reasoned into. It seems that those who succeed in harnessing a group's tribal instincts tend to defeat those who aim to rise above them. Policy-makers could benefit from reading Greene's book, but anyone with an election to win might be better off with Bloom's focus on morality's automatic weaponry.

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Correspondence to John Whitfield.

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Whitfield, J. Psychology: The appetite for right. Nature 502, 622–623 (2013).

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