Why is it against the law to sell chewing gum or to not flush a toilet in Singapore, but completely legal to smoke pot in the Netherlands? Anthropologists have developed a spectrum, called the tightness-looseness scale, to explain this kind of cultural variation. "Tight" countries have strong social norms, don’t tolerate much deviant behavior, and enforce strict rules and conventions. Meanwhile, "loose" nations have weaker social norms and are more permissive.
But what actually determines the type of culture that nations have? A study published in Science last week finds that where a nation falls on the tightness-looseness spectrum has much to do with its ecological, historical, and societal threats.