Can you name the six basic emotions? Take a straw poll of your friends and we guarantee that you will find no consensus. Yet psychologists are unequivocal: joy, sadness, anger, fear, surprise and disgust. These are the Big Six, quite literally the in-your-face emotions - the ones that everyone exhibits with the same characteristic facial expressions. They have been the subjects of intense research for more than half a century, not least because of the role they have played in our survival as a species. Times have changed, though. We live in a more subtle world in which other emotions have come to the fore.
In the midst of last year's economic turmoil, the US president Barack Obama's inauguration speech was inspiring stuff. Some of his supporters, hanging on his every word, will have had tears in their eyes, a tingling sensation on the back of their necks and a warm feeling in their chest as though it was opening up to let love and hope flood out. This feeling is what Jonathan Haidt, at the University of Virginia, Charlottesville, has labelled "elevation".
But to be considered as a basic emotion it should also have a purpose. If emotions are to fulfil their role as survival aids, they must motivate activities that help us thrive. So what is elevation for? Prof Haidt's idea was born of the choked feelings that people often report when they describe experiencing elevation. This hints that the vagus nerve is involved because it is responsible for stimulating the throat and neck muscles. Activation of the vagus nerve is also linked to the release of a hormone called oxytocin, which generates warm, calm feelings - just the sort associated with elevation. So elevation has a physiological component and motivational one, too. However, unlike the Big Six emotions, it does not have an obvious characteristic facial expression, which may explain why it has slipped under the research radar for so long.
Your head tilts to one side, your speech quickens and the muscles in your forehead and around your eyes contract as you become engrossed in mastering a bassoon sonata, understanding the thermodynamics of the universe, or perhaps just browsing through your stamp collection. Interest may be trickier to pin down than fear or joy but it nevertheless possesses one of the hallmarks of a basic emotion - its own facial expression. Since the 1960s when Paul Ekman pioneered the field, psychologists have looked for universal, characteristic facial expressions to help measure and classify emotions. Interest also seems to have a purpose. Paul Silvia, a psychologist at the University of North Carolina, at Greensboro, believes it motivates people to learn - not for money, not for an exam, but for its own sake, to increase their knowledge just because they want to.
Gratitude has some way to go before it satisfies the most stringent emotion criteria. The facial expression has yet to be identified, although it is easy to speculate what it might involve - a smile and a dip of the head, perhaps. Like all emotions worth their salt, though, gratitude motivates us to act: it makes us want to acknowledge and repay a kindness or thoughtful gesture. So gratitude might simply ensure a quid pro quo repayment mechanism, but new research suggests that there might be more to it than that. Sara Algoe, of the University of North Carolina, at Chapel Hill, has found that gratitude makes cohabiting couples feel more connected. If Prof Algoe is correct, gratitude has big potential benefits in the modern world. High-quality relationships are good for our health, her colleague Barbara Fredrickson points out.
It is a feeling we have all experienced, whether in a lecture theatre, an art gallery or walking in an unfamiliar city, but confusion is tricky to describe. Dacher Keltner, at the University of California, Berkeley, suggests that it is the "feeling that the environment is giving insufficient or contradictory information". But is confusion really an emotion? For some psychologists, the idea is scandalous. Others describe confusion as the fringiest of the fringe. Nevertheless, Prof Silvia thinks there is a good case to be made for considering confusion as a basic emotion, not least because it is so easy to spot. The brow furrows, the eyes narrow, the lip might even get bitten - you know confusion when you see it. In fact, one study found it was the second most recognisable everyday expression, only surpassed by joy. What, then, is confusion for? He believes it is our brain's way of telling us that the way we are thinking about things is not working, that our mental model of the world is flawed or inadequate. Sometimes this will make us withdraw, but it can also motivate us to shift our attention or change our learning strategy, he says.
The conceited, arrogant feeling of pride has been called the deadliest of the seven deadly sins. Yet pride can also be noble. That is why Jessica Tracy, at the University of British Columbia in Vancouver, Canada, one of the few psychologists focused on pride, makes the distinction between what she calls "hubristic pride" and "authentic pride".
Pride may manifest itself in two ways, but we cannot tell these apart by their outward appearance, she says. So what is the point of pride, and why do we have two prides that feel different but look the same? In general, when people see pride expressed they associate it with high status. So pride motivates us to do well so that we gain respect. There are two distinct ways to do this, which perhaps explains the flip sides of pride.