46 | New Scientist | 20 November 2021
we good and evil?”, page 40): a
tendency to seek and accept evidence
that supports what we already believe.
“You 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,” says Steven Pinker
at Harvard University, author of
Rationality: What it is, why it seems
scarce, why it matters.
On an individual level, such
“motivated reasoning” 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.
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,T
AKE a look at the data to the
right, 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’s 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’t 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 “Why are“ THERE IS LITTLE EVIDENCE THAT
IRRATIONALITY IS ON THE MARCH”
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’t
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 – 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. Graham LawtonWhy are we
irrational?
Crime rate increased Crime rate decreased
Gun control 75 223
No gun control 21 107
How does banning concealed handguns
influence crime rates in US cities?
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