Wake up, sleepy head, it’s time to become morally lucid (Image: Loeiza Jacq/Millennium)

Read more: Special report: Morality put to the test

We should embrace rather than fear the knowledge science brings as it unravels morality’s muddles, says Fiery Cushman

A LUCID dream has three phases. First you experience the dream as reality. Then you recognise it as a product of your mind. Finally, you gain the power of control.


Morality is proceeding along similar lines. We have long thought of moral laws as fixed points of reality, self-evident truths rooted in divine command or in some Platonic realm of absolute rights and wrongs. But new research is offering an alternative, explaining moral attitudes in the context of evolution, culture and the neural architecture of our brains. This apparent reduction of morality to a scientific specimen can seem threatening, but it needn’t. Rather, by unmasking our minds as the authors of morality, we may be better able to bend its narrative arc towards a happy end.

One way to do this is to recognise the ways in which evolution has shaped morality. Social psychologist Jonathan Haidt asked students at the University of Virginia in Charlottesville to imagine a brother and sister engaging in secret, consensual, protected sex. Would that be wrong, he asked? Most thought so. But when asked why, the students floundered. Protection meant no threat of disabled children, and secrecy brought no possibility of embarrassment. The pair had no regrets – it was consensual. So how is it wrong? Perhaps incest is simply an arbitrary taboo, passed on through religion, law, parents and peers.

But another possibility is that humans have an evolved aversion to incest because such unions tend to produce less-fit offspring.

Debra Lieberman, an evolutionary psychologist at the University of Miami in Florida, tested these rival hypotheses with an ingenious experiment (Proceedings of the Royal Society of London B, vol 270, p 819). She considered the ways in which evolution could have built in a “sibling detector”. For older siblings, it is easy: just watch who your mother gives birth to and raises. For younger siblings a subtler strategy is needed: note how many years you live in the same household as other children.

Lieberman asked over 1000 people how much the thought of incest disgusted them, and the results were clear as day: older siblings were uniformly disgusted by the thought, while younger siblings’ disgust was a linear function of years of cohabitation. Then Lieberman showed that unrelated children reared together in Israeli kibbutzim develop sexual aversions according to the same factors, even though there is no cultural taboo against relationships between them. Finally, she showed that people’s moral outrage when contemplating others engaging in incest was predicted by the level of aversion they would feel towards intercourse with their own siblings, again based on those two factors. In short, it seems that the moral injunction against incest is a product of a specifically evolved mechanism to prevent sibling sex.

Theories about the biological evolution of morality have been around for some time, but a very recent area of research is into the cultural evolution of morality. Just as we inherit genes from our parents, we inherit values from cultural sources. And just as genes adapt to environments, values evolve to match the structure of social life.

In a striking study, a team led by anthropologist Joseph Henrich at the University of British Columbia in Vancouver, Canada, used simple economic games to probe moral norms in 15 societies, from the Amazon to Siberia. A game might ask, if I loan you $10 so that you can convert it into $30, how much of the profit will you return to me? The team found large differences in levels of giving, trust and reciprocity among different societies, and these social norms correlate with their economic practices. Cultures that exhibit strong bonds of mutual trust between individuals and enforce them with punishment for non-compliance also practice division of labour and the exchange of goods in open markets, ultimately leading to economic wealth (Science, vol 327, p 1480).

Both biological and cultural evolution attempt to explain morality in terms of adaptive design principles, but another line of research illustrates how sophisticated moral principles can rest on accidents of cognitive architecture. Consider the distinction between actions and omissions. Most people think it is worse to actively harm than to passively allow a harm to occur.

For instance, the US Supreme Court and the American Medical Association prohibit active euthanasia, such as administering morphine, but allow passive euthanasia, such as terminating dialysis. But the patient is just as dead either way, so why make this distinction?

Surprisingly, it may have less to do with morality per se than with how we understand causation. People generally think that actions cause outcomes in a direct way that omissions do not. If I roll a bowling ball past your feet and you don’t stop it, it seems more appropriate to say that I caused the pins to fall rather than you. If we replace the pins with a person’s ankle, it seems appropriate to say that I caused the injury – even though you could have prevented it. Because judgements of moral responsibility often begin with a determination of causal responsibility, I receive greater blame.

When I and a team of neuroscientists used fMRI to investigate such judgements, we found that a large network of brain regions exhibits greater activity when judging omissions than when judging actions. Many of these regions are associated with deliberate, effortful, logical thinking. The more activity a person exhibited in these regions, the more likely they were to say that harm by omission is morally wrong. In short, it looks like judging a harmful action is relatively easy, while judging a harmful omission is hard work. This may reflect the fact that causal responsibility is much more obvious in the active cases – a feature of the brain’s design with major consequences for law and policy.

All the studies I have described share a common view: moral rules are born in human minds. For many, this is deeply threatening. Moral rules must be immutable and eternal, they say, like the speed of light or the mass of a proton. Otherwise, why should we obey them?

These studies all suggest that moral rules are born in human minds. For many, this is deeply threatening

As we come to a scientific understanding of morality, society is not going to descend into anarchy. Instead, we may be able to shape our moral thinking towards nobler ends. Which norms of fairness foster economic prosperity? What are the appropriate limits on assisting a patient’s end-of-life decisions? By recognising morality as a property of the mind, we gain a magical power of control over its future.