麻豆传媒

TAKE a look at the data below, showing crime rates in US cities according to whether or not they ban concealed handguns. Based on these numbers, would you conclude that gun control reduces crime? Take as much time as you want.

If you answered no, give yourself a pat on the back. Most people answer yes, dazzled by the large number of cities with gun control and decreasing crime. But what matters is the proportion of cities with falling crime. That鈥檚 75 per cent for cities with gun control and 84 per cent for those without. The rational conclusion is that gun control increases crime, or at least doesn鈥檛 decrease it.

Before you punch the air or a passer-by, the data is fake. But faced with it, supporters of gun control are more likely to jump to the wrong conclusion. Opponents of gun control scrutinise the data more cautiously and more often spot the real pattern.

The test is designed to winkle out a pervasive and intractable source of human irrationality, the myside bias. It expresses the tribal thinking that evolution has gifted us (see 鈥淲hy are we good and evil?鈥�): a tendency to seek and accept evidence that supports what we already believe. 鈥淵ou direct your reasoning to end up with a conclusion that is already a sacred belief or a shibboleth in your side, your team, your coalition, your party, your posse,鈥� says Steven Pinker at Harvard University, author of Rationality: What it is, why it seems scarce, why it matters.

On an individual level, such 鈥渕otivated reasoning鈥� is generally fairly harmless, but once promoted to group level, it can unleash chaos. The obvious example is climate change, where positions are determined almost completely by politics and denial is impervious to scientific facts.

鈥淭here is little evidence that irrationality is on the march鈥�

Yet there is no reason to conclude that humans are fundamentally irrational. Our brains evolved to deal with proximate dangers to our own survival and that of our kith and kin. In performing life tasks such as holding down a job and putting food on the table, most of us act rationally for the majority of the time. A gradual, distant danger such as climate change, however, pertains to the world beyond immediate experience. This contains the deep past and far future, the microscopic and cosmic, distant peoples and places, the goings-on in palaces and corridors of power. Here, we generally have no way of knowing the answers but still desire them.

We have developed many tools to analyse such situations rationally: logic, probability, Bayesian reasoning, game theory, correlation versus causation and so on. But these don鈥檛 come naturally to us. We often fall back on conjecture, in the form of exciting, morally charged stories, a mode of thinking that furnishes the world with paranormal beliefs, fake news and conspiracy theories.

Are they now gaining the upper hand? There is little evidence behind the widespread perception that irrationality is on the march, says Pinker 鈥� just as there is little evidence that the tools of enlightened reasoning have seriously reduced the global prevalence of codswallop. The problem is, we look at the available data and see what we want to see.