Why on Earth would a working-class person ever vote for a conservative candidate? This question has obsessed the American left since Ronald Reagan first captured the votes of so many union members, farmers, urban Catholics and other relatively powerless people – the so-called "Reagan Democrats". Isn't the Republican party the party of big business? Don't the Democrats stand up for the little guy, and try to redistribute the wealth downwards?

Many commentators on the left have embraced some version of the duping hypothesis: the Republican party dupes people into voting against their economic interests by triggering outrage on cultural issues. "Vote for us and we'll protect the American flag!" say the Republicans. "We'll make English the official language of the United States! And most importantly, we'll prevent gay people from threatening your marriage when they … marry! Along the way we'll cut taxes on the rich, cut benefits for the poor, and allow industries to dump their waste into your drinking water, but never mind that. Only we can protect you from gay, Spanish-speaking flag-burners!"

One of the most robust findings in social psychology is that people find ways to believe whatever they want to believe. And the left really want to believe the duping hypothesis. It absolves them from blame and protects them from the need to look in the mirror or figure out what they stand for in the 21st century.

Here's a more painful but ultimately constructive diagnosis, from the point of view of moral psychology: politics at the national level is more like religion than it is like shopping. It's more about a moral vision that unifies a nation and calls it to greatness than it is about self-interest or specific policies. In most countries, the right tends to see that more clearly than the left. In America the Republicans did the hard work of drafting their moral vision in the 1970s, and Ronald Reagan was their eloquent spokesman. Patriotism, social order, strong families, personal responsibility (not government safety nets) and free enterprise. Those are values, not government programmes.

The Democrats, in contrast, have tried to win voters' hearts by promising to protect or expand programmes for elderly people, young people, students, poor people and the middle class. Vote for us and we'll use government to take care of everyone! But most Americans don't want to live in a nation based primarily on caring. That's what families are for.

One reason the left has such difficulty forging a lasting connection with voters is that the right has a built-in advantage – conservatives have a broader moral palate than the liberals (as we call leftists in the US). Think about it this way: our tongues have taste buds that are responsive to five classes of chemicals, which we perceive as sweet, sour, salty, bitter, and savoury. Sweetness is generally the most appealing of the five tastes, but when it comes to a serious meal, most people want more than that.

In the same way, you can think of the moral mind as being like a tongue that is sensitive to a variety of moral flavours. In my research with colleagues at YourMorals.org, we have identified six moral concerns as the best candidates for being the innate "taste buds" of the moral sense: care/harm, fairness/cheating, liberty/oppression, loyalty/betrayal, authority/subversion, and sanctity/degradation. Across many kinds of surveys, in the UK as well as in the USA, we find that people who self-identify as being on the left score higher on questions about care/harm. For example, how much would someone have to pay you to kick a dog in the head? Nobody wants to do this, but liberals say they would require more money than conservatives to cause harm to an innocent creature.

But on matters relating to group loyalty, respect for authority and sanctity (treating things as sacred and untouchable, not only in the context of religion), it sometimes seems that liberals lack the moral taste buds, or at least, their moral "cuisine" makes less use of them. For example, according to our data, if you want to hire someone to criticise your nation on a radio show in another nation (loyalty), give the finger to his boss (authority), or sign a piece of paper stating one's willingness to sell his soul (sanctity), you can save a lot of money by posting a sign: "Conservatives need not apply."

In America, it is these three moral foundations that underlie most of the "cultural" issues that, according to duping theorists, are used to distract voters from their self-interest. But are voters really voting against their self-interest when they vote for candidates who share their values? Loyalty, respect for authority and some degree of sanctification create a more binding social order that places some limits on individualism and egoism. As marriage rates plummet, and globalisation and rising diversity erodes the sense of common heritage within each nation, a lot of voters in many western nations find themselves hungering for conservative moral cuisine.

Despite being in the wake of a financial crisis that – if the duping theorists were correct – should have buried the cultural issues and pulled most voters to the left, we are finding in America and many European nations a stronger shift to the right. When people fear the collapse of their society, they want order and national greatness, not a more nurturing government.

Even on the two moral taste buds that both sides claim – fairness and liberty – the right can often outcook the left. The left typically thinks of equality as being central to fairness, and leftists are extremely sensitive about gross inequalities of outcome – particularly when they correspond along racial or ethnic lines. But the broader meaning of fairness is really proportionality – are people getting rewarded in proportion to the work they put into a common project? Equality of outcomes is only seen as fair by most people in the special case in which everyone has made equal contributions. The conservative media (such as the Daily Mail, or Fox News in the US) is much more sensitive to the presence of slackers and benefit cheats. They are very effective at stirring up outrage at the government for condoning cheating.

Similarly for liberty. Americans and Britons all love liberty, yet when liberty and care conflict, the left is more likely to choose care. This is the crux of the US's monumental battle over Obama's healthcare plan. Can the federal government compel some people to buy a product (health insurance) in order to make a plan work that extends care to 30 million other people? The derogatory term "nanny state" is rarely used against the right (pastygate being perhaps an exception). Conservatives are more cautious about infringing on individual liberties (eg of gun owners in the US and small businessmen) in order to protect vulnerable populations (such as children, animals and immigrants).

In sum, the left has a tendency to place caring for the weak, sick and vulnerable above all other moral concerns. It is admirable and necessary that some political party stands up for victims of injustice, racism or bad luck. But in focusing so much on the needy, the left often fails to address – and sometimes violates – other moral needs, hopes and concerns. When working-class people vote conservative, as most do in the US, they are not voting against their self-interest; they are voting for their moral interest. They are voting for the party that serves to them a more satisfying moral cuisine. The left in the UK and USA should think hard about their recipe for success in the 21st century.

Jonathan Haidt is a professor of psychology at New York University's Stern School of Business. He is the author of The Righteous Mind: Why Good People are Divided by Politics and Religion. To take the survey described in this essay, visit www.yourmorals.org/express_welcome_sacredness.php