In the wake of the Brexit referendum, many people across the globe have expressed bewilderment at what they see as Leave voters’ irrational decision-making. Headlines and commentaries abound accusing Leavers of voting against their self-interest. Urban Dictionary, the crowdsourced online dictionary of slang, now even defines “Brexit” as “shorthand for ‘shooting yourself in the foot’”.

If self-interest is defined in purely economic terms, there may be some truth in these accusations. But psychologists have long known that humans consider far more than their pocketbooks when making decisions. One of the clearest demonstrations of this comes from the ultimatum game. The game is simple: one player, the “proposer”, is given some money and proposes a way to split the pie with a second player, the “responder”. The responder has a choice: she can accept the proposer’s offer, in which case both players are paid accordingly. Or, she can reject the offer, in which case neither player gets any money.

Classical economic theories, which dictate that people always act in their self-interest and define self-interest purely in terms of money, make a very strong and straightforward prediction about behavior in the ultimatum game. Since some money is always better than no money, responders should always accept any nonzero offer.

However, in reality humans play the game very differently: responders overwhelmingly reject offers they perceive to be unfair, usually around less than 30% of the stake. Many would rather end up with nothing than accept the losing end of a bad deal. This behaviour is observed across many different cultures and emerges at a young age. The aversion to unfair treatment is so strong that people are willing to give up as much as a few months’ wages to reject unfair offers.

When Werner Güth published the first ultimatum game studies in 1982, economists were shocked – just as Brexit commentators are now flabbergasted by the referendum results. Both failed to appreciate that people often disregard economic self-interest in order to express their emotions and their identities.

Recent interviews with Leave voters reveal that their choice was deliberately considered and driven by far more than economics. “I voted leave for empowerment, and to feel like my voice is heard,” said one voter. Another cited a desire for “regaining control over our own destiny”. Some thought their vote would not influence the referendum’s outcome. Others assumed that any negative economic consequences of leaving the EU would have little impact on their already dire situation. Thus many Leave voters saw their choice as a tradeoff between the potential financial costs of leaving the EU, which many perceived as negligible, and the immediate, emotional benefits of expressing their outrage at metropolitan elitism and an economic system that has richly rewarded the few at the expense of the many: “It was a chance to kick the whole establishment where it hurt, for us to send pain the other way”. Viewed through this lens, the referendum results seem less surprising.

Research on the power of self-expression indeed shows that the urge to communicate frustration often dominates economic self-interest. In one recent study, participants were asked how much they agreed with statements like “I do not want someone to interfere with my business” and “I do not like having someone else’s opinion imposed on me”. Those participants who strongly agreed with such statements were far more likely to reject unfair offers in the ultimatum game. These findings are consistent with recent reports that a majority of Leave voters were motivated by concerns about sovereignty: “the ability of Britain to make its own laws” was the primary reason they rejected the EU.

The desire to express anger over unfair outcomes can be so strong that the consequences for those in power matter little. The impunity game is identical to the ultimatum game apart from one important distinction: responders’ choices affect only their own payoffs. Thus, when a responder rejects an offer from a proposer in the impunity game, she forgoes her own payoff but the proposer still keeps his payoff. Many responders nevertheless reject unfair offers in the impunity game – even when their decisions are known only to themselves. They would rather have nothing than signal to themselves that they are willing to accept a raw deal. Such behaviour parallels the explanations of Leave supporters who voted to prove something to themselves: one commenter wrote, “The only way I could live with myself, is a vote for OUT!”

Sadly, some Leave voters are now regretting their decisions. While the emotional benefits of self-expression are immediate, they may be short-lived; meanwhile, the economic and social costs of Brexit will be felt for generations to come. Could this outcome have been avoided?

Research using another variant of the ultimatum game shows people are less likely to hurt themselves financially when given alternative ways to express frustration with inequality. One group of responders played the game as usual, deciding whether to accept or reject offers from proposers. A second group of responders played the same game, and also had the opportunity to send a written note to the proposers. The first group of responders rejected unfair offers 60% of the time. But the second group, who had an alternative channel for expressing their displeasure, rejected the same unfair offers only 30% of the time. Rather than signaling their outrage via rejection, they sent critical messages instead, writing notes like “Why do you have to be greedy?” and “Too selfish. I would rather get nothing and let you get a penny.”

One important difference between responders and Leavers is that responders know exactly who is responsible for their economic fate. Leavers may feel especially frustrated because there is no single person or institution to blame for their situation. Can self-expression defuse anger even when it can’t be directed toward those responsible for inequality? A recent study suggests yes. Responders playing the ultimatum game were given the opportunity to send a message to a third party before the proposers made their offers. Specifically, they were asked to write “what they would have told the proposer if they had the chance.” The results were striking. Responders were far less likely to reject unfair offers when they were able to voice their opinions, despite knowing the proposers would never receive those messages. Sending messages allowed responders to accept unfair offers while proving to themselves they are no pushover. So powerful was the drive to preserve self-image that a majority of responders were willing to pay substantial amounts of money to send these messages.

The psychology of self-expression teaches us that people will use whatever channels are available to them to make their voices heard. Brexit illustrates the perils of linking those channels to the fate of the world economy. Frustration with economic inequality is not unique to the UK; similar sentiments fuel the growing popularity of Donald Trump in the USA and both far-left and far-right parties throughout Europe. Those who wish to engage with these voters would be well-advised to recognise the human need to feel that someone – anyone – is listening.

