Not long ago, as part of an experiment, an American psychologist named Sian Beilock recruited a number of female university students and asked them to take a maths test.

The women were divided into two groups, one of which was told that the purpose of the research was to understand why men, in general, do better than women at maths. The other group was given no such explanation. Here's what happened: the students who were reminded of the stereotype that women are worse at maths did worse at maths, performing 10-15% less well than the others.

The reason for their poor showing, Beilock argued, was the phenomenon known as "stereotype threat" - the way anxiety stops us succeeding precisely because we know we're expected to fail.

Even so, it's a little troubling to speculate whether many of us, whatever our race or gender, might not be subconsciously sabotaging ourselves because we've internalised the belief that being a certain sort of person entails demonstrating certain characteristics: