Some years ago a fascinating study found that people who score very poorly in tests often incorrectly estimate that they have in fact performed better than average.
By contrast those who performed very well often underestimate their performance relative to others.
This is known as the Dunning-Kruger effect. People who know very little about a subject are often completely ignorant of their shortcomings and are therefore the most likely to speak with misplaced confidence and authority.
Genuine experts, on the other hand, know only too well the extent of their ignorance.
As everyone’s favourite genius Einstein once said, “The more I learn, the more I realise how much I don’t know.”
This can have real world consequences – and not just when you get cornered at a party by a boorish know-all whose ill-informed opinions are unwittingly revealed with every mangled syllable.
Or when a contestant confidently strides up to the microphone in a singing contest only to murder a much loved ballad.
It can have devastating effects in areas such as personal finance when people are led to believe they can enjoy a higher standard of living while falling victim to predatory loans without even a rudimentary understanding of interest rates.
And it is causing havoc seemingly everywhere in the age of Brexit, anti-vaccine propaganda and climate change denial.
Donald Trump has been described as the Dunning-Kruger effect personified.
But perhaps the most famous – and most amusing – case of the Dunning-Kruger effect is that of McArthur Wheeler.
Wheeler embarked on two brazen bank robberies in Pittsburgh in 1995 in broad daylight – and without a disguise – in the mistaken belief that the lemon juice he had smeared on his face would obscure his identity on the security cameras.
When Wheeler was arrested that night he was dumbfounded that the magical properties of lemon juice had failed him. He had, after all, tested his theory by taking a photograph of himself with a Polaroid camera in which his face was not visible.
It turned out he was just not a good photographer – and had simply been out of shot.