There are two things most people will tell you about left-handedness. First, cultures around the world and across history have been wary of those born left-handed. The Latin word for “left side” was “sinister”, underlining the negative connotations of being born as such.

And, second, that left-handedness appears to be disproportionately represented among some ultra-successful people – four of the last five US presidents, for instance, have been left-handed. That is a startling figure, given that only around 10 per cent of Americans are thought to be left-handed.

But research, as ever, is the bane of popular perception. A new study by a Harvard economist, covered today in our business section, suggests that, except in certain unusual cases, left-handed people earn roughly 10 to 12 per cent less than right-handers. That’s equivalent to a skills and expertise difference of a year’s schooling. Some explain this by pointing to the early years of development. Left-handed children, they argue, are more prone to smudging their work when they write left to right. Therefore, they need to concentrate harder and persevere more, which are the sort of skills that result in high-functioning, high-achieving jobs in later life. This seems to make sense if you consider that US presidents Obama, Bill Clinton, George H W Bush and Ronald Reagan were all left-handed.

But what about left-handers who don’t concentrate on keeping their work smudge-free? Are they less hard-working and rightly condemned to earn less? No one knows.

In any case, the theory would make sense if we only considered languages that use the Latin script (English, French, Spanish etc). What about those that write right to left –Arabic, Persian, Urdu? And what about Azeri, which can be written in both Latin and Arabic scripts? Finally, here’s the real conundrum. Chinese is written top to bottom. For centuries, writing meant careful brushwork, not penmanship so leftie smudging was probably not much of an issue. And yet, in Mandarin, left still connotates the “bad” side.