ith a death toll over 2 million and nearly 100 million people infected worldwide, Covid-19 is still wreaking havoc even as vaccines are rolled out. Yet fatalities are far from evenly distributed. Some nations have effectively beaten the pandemic; others have been soundly beaten. Japan’s 126 million citizens have recorded just over 5,000 deaths. With a nearly identical population, Mexico has suffered more than 150,000 deaths and counting. What explains such stark differences? Wealth? Hospital capacity? Age? Climate? It turns out Covid’s deadliness depends on something simpler and more profound: cultural differences in our willingness to follow rules. All cultures have social norms, or unwritten rules for social behaviour. We adhere to standards of dress, discipline our kids, and don’t elbow our way through crowded subways not because these are legislative codes but because they help our society function. Psychologists have shown that some cultures abide by social norms quite strictly; they’re tight. Others are loose – with a more relaxed attitude toward rule-breakers. This distinction, first noticed by Herodotus, is in modern times capable of being quantified by psychologists and anthropologists. Relative to the US, the UK, Israel, Spain and Italy, countries like Singapore, Japan, China and Austria have been shown to be much tighter. These differences aren’t random. Research in both nation-states and small-scale societies has shown that communities with histories of chronic threat – whether natural disasters, infectious diseases, famines or invasions – develop stricter rules that ensure order and cohesion. It makes good evolutionary sense: following rules helps us survive chaos and crisis. On the flipside, looser groups that have faced fewer threats can afford to be more permissive. Neither type is better or worse – until a global pandemic hits. Back in March, I started to worry that loose cultures, with their rule-breaking spirit, would take longer to abide by public health measures, with potentially tragic consequences. I was hopeful that they would eventually tighten. All of our computer models prior to Covid suggested they would. But they didn’t. In research that tracked more than 50 countries, published this week in the Lancet Planetary Health, my team and I show that, taking into account other factors, loose cultures had five times the number of cases that tight cultures did, and more than eight times as many deaths. Remarkably, our analysis of data from the UK firm YouGov revealed that people in loose cultures had far less fear of the Covid-19 virus throughout 2020, even as cases skyrocketed. In tight nations, 70% of people were very scared of catching the virus. In loose cultures, only 49% were. Reality never bit in these populations in part because people in cultures that are adapted to low levels of danger didn’t respond as swiftly to the “threat signal” embodied by the pandemic when it came. This can happen in nature too. The most infamous case is the fearless dodo bird of Mauritius, which, having evolved without predators, became extinct within a century of its first contact with humans. The dodo’s story shows that traits honed in one environment can become a liability when the environment changes. This is what scientists call an evolutionary mismatch, and it has led to thousands of unnecessary Covid-19 deaths in loose-leaning societies. Obviously, loose groups aren’t destined to disappear from the face of the earth. But their continuing struggles with a year-old pandemic shows the difficulties they are having in adapting. The virus has been especially effective at turning some societies’ propensity for rule breaking against them. Americans exemplify this spirit. It’s why the United States boasts a great deal of creativity and innovation. It’s also a major liability during times of threat. Such maverick behaviour is supposed to subside in emergencies. Yet countless US citizens continue holding parties, shopping maskless and generally scoffing at the virus. When the fear reflex is triggered, it’s often in a perverse way: fearing lockdowns and mask mandates more than the virus itself. These cultural mismatches made that threat signal harder to discern. But former President Trump’s messaging silenced it for millions. “Just stay calm. It will go away,” he said on 10 March 2020. Even in January 2021, well after more than 300,000 Americans had died, he complained of the Centers for Disease Control and Prevention’s supposed exaggerations. The British prime minister, Boris Johnson, also interrupted the fear reflex in the UK. As cases rose last March, he boasted: “I was at a hospital the other night where there were a few coronavirus patients, and I shook hands with everybody, you’ll be pleased to know, and I continue to shake hands … people obviously can make up their own mind.” Tragically, citing worries about “behavioural fatigue”, Johnson and his ministers deliberately enacted health measures slowly, essentially hitting the snooze button on the alarm citizens were supposed to feel. It’s no surprise that King’s College London found just one in 10 people in the UK who were exposed to a confirmed Covid-19 carrier are actually following orders to isolate for two weeks, or that fewer than one in five have been self-isolating after developing symptoms themselves. To minimise further Covid fatalities, and to ready ourselves for future collective threats – one expert called this a “dress rehearsal” for what is to come – loose nations must adapt and heed the right threat signals. We can begin by building cultural intelligence to outsmart the threat. Three actions are key. First, we need to shift the way we communicate about the type of threat we’re facing. We tighten quickly in response to vivid, concrete threats, such as warfare. By contrast, because germs are invisible and abstract, the threat signal is easier to ignore. Public health officials need to make Covid’s dangers vivid. Simply scaring people, however, can backfire: when we feel helpless, psychologists find that we adopt a defensive, passive posture. To persuade people to change their behaviour, we should be candid about Covid symptoms while also calling on our “can-do” spirit. Second, we need to make clear that tightening is temporary. A society of rule-breakers can get on board with tighter procedures if they know there’s an end in sight. The faster we tighten, the faster we’ll reduce the threat, and the faster we’ll restore freedom. What all nations need is what we call cultural ambidexterity: the ability to adjust how tight and loose they are based on how dangerous conditions are. New Zealand exemplifies this approach. Kiwis are famously loose, but they enacted some of the world’s strictest measures early on – and tamed their rule-breaking spirit, limiting Covid-19 deaths to just 25. Finally, we need to recognise that we’re all in this together. The Washington Post profiled one small town that exemplifies this approach. For months, Tangier Island in the Chesapeake Bay, Virginia, was free of cases. But when the outbreak hit, it united people in a powerful display of public health coordination. Resident Reta Pruitt captured the town’s ethos: “They’re taking it serious now. But that’s the whole trouble: the first time, we weren’t serious about it.” An evolutionary mismatch was thwarted just in time by compassion and coordination – and, above all, getting the threat signal right. • Michele Gelfand is a professor at the University of Maryland, and the author of Rule Makers, Rule Breakers: How Tight and Loose Cultures Wire Our World