One of our most exploited biases is how we’re naturally drawn to negative information. There is an evolutionary element to this. Negative information tends to be more urgent, even life-threatening: we needed to take note when we were warned by our fellow cavepeople about a lurking sabre-toothed tiger (and those who didn’t were edited out of the gene pool). We are instinctive worriers, through natural selection.

Our brains handle negative information differently and store it more accessibly, as shown in many experiments that track electrical activity in subjects’ brains. We react more strongly to negative images, like mutilated faces or dead cats, and process them with different intensity in different parts of the brain.

Murder rates are actually decreasing significantly across the world – but that is not our perception. When we asked what people thought was happening to murder rates across 30 countries, only 15 per cent correctly said that they were declining, and nearly half said they were increasing. This is partly us communicating our worries. Psychologists suggest that when we worry and ruminate about something, we lose some elements of cognitive control, and the threat becomes bigger in our brains.

We also have a faulty view of change: in particular, we’re susceptible to a false sense that everything is going downhill. We naturally suffer from what social psychologists call ‘rosy retrospection’: we literally edit out bad things from our past, on everything from our poor exam results to our less-than-perfect holidays. The Romans referred to this phenomenon with the phrase memoria praeteritorum bonorum, which roughly translates as ‘the past is always well remembered’.

Again, this is not a dumb fault in our brains, it’s good for our mental health not to dwell on past failings or challenges. But it has the unfortunate side-effect of making us think the present and future are worse than our memories of the past.

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